Topic 11 · Physical and chemical change — the scripts
What you are deciding: go-ahead for video generation on this topic, card by card.
Out of scope: articles and PP100 items (not on this page).
Here: the intro video, 6 lesson videos (2 marked by the author as “could do without a video”) and the summary video, in teaching order. Each card: the script, the attached question, then the quiz the student meets after the video.
How: tap one button per card. Taps and notes save as you go and are sent; the Notes tab shows what has gone and re-sends.
Introduction: Physical and chemical change
Script
| Say | Screen |
|---|---|
| Here is a kitchen table. A sheet of paper lies on it, torn in two, and an ice cube has melted into a puddle. | [a kitchen table; the torn sheet; the ice cube melting to a puddle] |
| By the back door is an iron nail that has been outside for a month: orange, flaky, crumbling. | [the nail, rusted, by the door] |
| Something changed in all three. But is the stuff at the end still the stuff you started with? | [the paper, the puddle and the nail in a row; question mark] |
| One question sorts every change like these. | [the question mark stays] |
| To find out, we will look at changes that make new stuff, and changes that do not. | [the three scenes stay] |
| Okay, so are you ready to find the one question that tells them apart? | [the three replies appear] |
The ready line's poll — the attached item (no key; the intro teaches nothing)
Okay, so are you ready to find the one question that tells them apart?
- A Yes, let's go! — Great. Here we go.
- B Not sure yet — That's fine. We take it one change at a time.
- C Let me watch that again — Good idea. Watch it again, then come back.
Answer
No key. A poll: every reply is accepted with its friendly line.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Physical change: the same substance in a new form
MAT-062 · Physical change — Identify which changes are physical based on whether any new substance is formed.
Script
| Say | Screen |
|---|---|
| A student tears a sheet of paper into two pieces. | [a sheet of paper tears in two] |
| She lets an ice cube melt in a glass. | [an ice cube in a glass melts to liquid] |
| And she stirs a spoon of sugar into water until the grains vanish. | [a spoon stirs; the grains vanish] |
| In each case, is the substance you end with the same substance you started with? | [the three scenes in a row; question mark] |
| Yes, it is, every time. | [three ticks appear faintly] |
| Each torn piece is still paper: zoom in, and the same paper particles are there. | [paper_torn: the sheet, the pieces, the two zoom boxes] |
| Look at the glass: the liquid is water, the same water particles, now rearranged. | [ice_to_water: the before box, the after box] |
| She sips the sugar water: it tastes sweet, so the sugar is still there, spread among the water particles. | [sugar_into_water: the two boxes, then the mixture box] |
| She bends a copper wire into a hook. | [a wire bends into a hook] |
| It is still copper. | [the table row: yes] |
| But if an iron nail stays in the rain for a month, orange flakes grow that are not iron. | [the nail row: no] |
| A change in which no new substance forms is called a physical change. | [chip: PHYSICAL CHANGE] |
| So, here's what we've seen. A physical change is a change in which no new substance forms. | [the rule slide: the cases table with its ticks and one cross; chip PHYSICAL CHANGE; nothing else printed] |
| The size, the shape or the state changes, but the particles are the same particles, arranged or moving differently. | [the three after boxes side by side] |
| So the torn paper, the melted ice and the dissolved sugar are three physical changes. | [the three scenes, each ticked under 'the same substance?'] |
| Okay, now your turn. | [closing screen: bullets — • A physical change: no new substance forms • The particles are the same particles, arranged or moving differently] |
“Okay, now your turn.” — the attached question
A sheet of paper is torn in two. What is in each piece?
- A the same paper particles
- B new particles that are not paper
- C no particles at all
Answer
Key: A — the same paper particles
Each piece is still paper.
So each piece holds the same paper particles.
Feedback per option
- A Each piece is still paper: the same paper particles are there.
- B Tearing makes pieces; it makes no new particle.
- C Every piece of paper is made of paper particles.
Quiz after the video — the mastery check, 14 items
A popsicle left on a plate turns into a puddle of liquid. Which change of state is this?
- A freezing
- B melting
- C evaporating
Answer
Key: B — melting
It became a liquid.
A solid turning into a liquid is called melting.
Feedback per option
- A Freezing is a liquid turning into a solid; here a solid turned into a liquid.
- B A solid turning into a liquid is melting.
- C Evaporating is a liquid turning into a gas; here a solid turned into a liquid.
Salt is stirred into water until no grains are left. The water is then left to evaporate. What is left in the dish?
- A nothing at all
- B a new white powder that is not salt
- C the salt
Answer
Key: C — the salt
Evaporating turns the water into a gas that leaves the dish.
The salt particles stay behind, so the salt is left in the dish.
Feedback per option
- A The water left as a gas, but the salt particles cannot; they stay in the dish.
- B Dissolving made no new substance; the powder left behind is the salt.
- C The salt particles were spread through the water; when the water leaves as a gas, the salt is left behind.
A steel shovel left out in the rain grows orange, flaky patches that crumble. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: B — not a physical change
Steel is shiny and gray and bends; the orange flakes are dull and crumble.
A new substance formed, so this is not a physical change.
Feedback per option
- A Steel is gray and bends; the orange flakes crumble. A new substance formed.
- B The orange flakes have properties steel does not have, so a new substance formed.
A stick of lip balm melts into a soft puddle in a warm pocket. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: A — physical change
The soft puddle is still lip balm, now a liquid instead of a solid.
No new substance formed, so this is a physical change.
Feedback per option
- A The puddle is still lip balm; only the state changed.
- B Melting changes the state, not the substance: the puddle is still lip balm.
A cucumber is sliced into thin rounds. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: A — physical change
Each round is still cucumber.
No new substance formed, so slicing is a physical change.
Feedback per option
- A Each round is still cucumber; only the size and shape changed.
- B Slicing makes pieces of the same substance: each round is still cucumber.
A banana peel turns brown, then black, over three days. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: B — not a physical change
The yellow peel became black and soft: properties it did not have before.
A new substance formed, so this is not a physical change.
Feedback per option
- A The black, soft peel has properties the yellow peel did not have: a new substance formed.
- B The peel did not only change shape or state; new substances with new properties formed in it.
A new, shiny penny turns dull brown after a year in a drawer. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: B — not a physical change
The shiny metal grew a dull brown layer that was not there before.
A new substance formed on the penny, so this is not a physical change.
Feedback per option
- A The dull brown layer is a substance that was not there on the shiny penny.
- B The shiny metal grew a dull brown layer with new properties: a new substance formed.
A glass jar falls and shatters into sharp pieces. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: A — physical change
Every sharp piece is still glass.
No new substance formed, so shattering is a physical change.
Feedback per option
- A Every piece is still glass; only the size and shape changed.
- B Shattering makes pieces of the same substance: every piece is still glass.
A spoonful of powdered drink mix stirred into water vanishes, and the water tastes of the mix. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: A — physical change
The water tastes of the mix, so the mix's particles are still there, spread through the water.
No new substance formed, so dissolving is a physical change.
Feedback per option
- A The taste says the drink mix is still there, spread through the water.
- B Dissolving spreads the drink mix's particles among the water particles; the mix is still the mix.
A firework bursts into colored light and leaves a cloud of smoke. Is this a physical change?
- A physical change
- B not a physical change
Answer
Key: B — not a physical change
The packed powder became smoke and burnt leftovers with different properties.
New substances formed, so this is not a physical change.
Feedback per option
- A The smoke and the burnt leftovers are not the powder that was packed inside: new substances formed.
- B The packed powder became light, smoke and ash, substances that were not there before.
Each size and shade of circle is a different kind of atom; touching circles are joined. The boxes show the particles before and after a change. Is the substance after the change the same substance?
- A yes
- B no
Answer
Key: A — yes
After, every particle is the same shape, only laid out differently.
The same particles, so the same substance: yes.
Feedback per option
- A Every particle after is the same shape as every particle before: the same substance, rearranged.
- B Compare the shapes: every particle after is one large open circle joined to two small dark circles, the same as before.
Each size and shade of circle is a different kind of atom; touching circles are joined. The left box shows the particles before a change; the right box shows a sample of what is left after it. Is the sample the same substance?
- A yes
- B no
Answer
Key: B — no
After, every particle is one gray circle joined to one large open circle.
New particles formed, so not the same substance: no.
Feedback per option
- A Before, the gray circles and the open pairs were apart; after, every particle is a gray circle joined to an open circle: a new particle.
- B The atoms joined into a new kind of particle, so the substance after is not the same.
Mateo stirs a spoon of salt into soup until no grains are left. He says: "The salt is destroyed; it has stopped existing." Is Mateo correct?
- A yes
- B no
Answer
Key: B — no
Those particles spread through the soup, which is why the soup tastes salty.
No new substance formed and nothing was destroyed, so Mateo is not correct.
Feedback per option
- A Out of sight is not destroyed. The salt particles are spread among the soup's particles; the soup tastes salty.
- B The salt particles are still there, spread among the soup's particles; the soup tastes salty, and evaporating the water would leave the salt.
A change in which no new substance forms, only the size, the shape or the state, is called a…
Typed answer
Answer
Accepted: physical change · a physical change · physical
The particles are the same particles, arranged or moving differently.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Chemical change: a new substance forms
MAT-063 · Chemical change — Identify which changes are chemical based on whether a new substance with different properties is formed.
Script
| Say | Screen |
|---|---|
| An iron nail left out for a month turns orange-brown and flaky. | [a shiny nail; a month passes; orange flakes grow] |
| Iron is shiny gray, bends without breaking, and a magnet pulls it hard. | [the shiny nail bends; a magnet grabs it] |
| The flakes are dull, crumble in your fingers, and a magnet barely pulls them. | [flakes crumble; the magnet barely moves them] |
| They are not iron in a new shape. What are they? | [question mark over the flakes] |
| They are a new substance, and the table shows it: every property differs. | [iron_rust_table fills row by row] |
| Iron atoms in the nail joined with oxygen atoms from the air. | [iron_to_rust: the iron box, the oxygen box] |
| The joined atoms make particles of a new substance, called rust. | [the rust box appears below; chip: RUST] |
| Rust is not iron with oxygen stuck on top: the atoms joined into new particles. | [stuck_on_vs_joined, both boxes under the question A NEW SUBSTANCE?] |
| A change in which a new substance forms is called a chemical change. | [chip: CHEMICAL CHANGE] |
| Ask the same question of every change: did a new substance form? | [l02_cases_table, empty last column] |
| Wood burning to ash, baking soda fizzing with a new gas, an egg frying solid: each gets a yes. | [the three yes rows fill together] |
| Ice melting to water, salt dissolving: each gets a no. | [the two no rows fill together] |
| So, a chemical change is a change in which a new substance forms. | [the rule slide: the rust box; chip CHEMICAL CHANGE; nothing else printed] |
| The new substance has its own properties, different from the substance you started with. | [iron_rust_table beside the rust box] |
| So the rusting nail is a chemical change. | [the nail, the rust box, chip: CHEMICAL CHANGE] |
| Okay, now your turn. | [closing screen: bullets — • A chemical change: a new substance forms • The new substance has its own properties] |
“Okay, now your turn.” — the attached question
An iron nail rusts. What do the iron atoms do?
- A They stay iron, with oxygen sitting on top of them.
- B They melt into orange flakes.
- C They join with oxygen atoms and make rust.
Answer
Key: C — They join with oxygen atoms and make rust.
Iron atoms in the nail join with oxygen atoms.
The joined atoms make particles of a new substance, rust.
Feedback per option
- A If oxygen only sat among the iron atoms, the iron would still be iron.
- B Nothing melts; the atoms join into new particles.
- C Iron atoms join with oxygen atoms: particles of a new substance, rust.
Quiz after the video — the mastery check, 13 items
Modeling clay is rolled from a ball into a long snake. Is this a physical change?
- A yes
- B no
Answer
Key: A — yes
The long snake is still clay: only the shape changed.
So rolling the clay is a physical change.
Feedback per option
- A The snake is still clay; only the shape changed, so no new substance formed.
- B A new shape is not a new substance. The snake is still clay, so no new substance formed: a physical change.
Water is a compound of hydrogen and oxygen. Hydrogen is a gas that burns. Does water burn like hydrogen?
- A yes
- B no
Answer
Key: B — no
New particles behave in new ways.
So water does not burn like hydrogen; it puts fires out.
Feedback per option
- A Being made from hydrogen does not make water burn. A compound is not like the elements it is made from; water puts fires out.
- B A compound is not like the elements it is made from; water puts fires out.
A knitted scarf is unraveled back into a long strand of yarn. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
The strand is the same yarn the scarf was made of.
No new substance formed, so unraveling is a physical change.
Feedback per option
- A The yarn is the same yarn the scarf was knitted from; no new substance formed.
- B Unraveling changes the shape only: the strand is still the same yarn.
A steel gate hinge left in the weather grows orange, crumbly patches that a magnet barely pulls. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
Steel is gray and a magnet pulls it hard; the patches are orange, crumbly and barely pulled.
A new substance formed, so this is a chemical change.
Feedback per option
- A Steel is gray and a magnet pulls it hard; the crumbly orange patches are a different substance.
- B The orange patches have properties steel does not have: a new substance formed.
A sparkler burns with bright sparks and leaves a black, brittle wire. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
The sparkler's coating became sparks, smoke and a black, brittle crust.
New substances formed, so burning the sparkler is a chemical change.
Feedback per option
- A The gray coating became sparks, smoke and a black crust: substances that were not there before.
- B The coating on the wire became new substances with new properties.
A carrot is grated into thin shreds. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
Every shred is still carrot.
No new substance formed, so grating is a physical change.
Feedback per option
- A Every shred is still carrot; only the size and shape changed.
- B Grating makes pieces of the same substance: every shred is still carrot.
A rubber band is stretched to twice its length. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
The stretched band is still rubber.
No new substance formed, so stretching is a physical change.
Feedback per option
- A The stretched band is still rubber; only the shape changed.
- B Stretching changes the shape only: the band is still rubber.
The cut face of an avocado turns brown within an hour. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
The pale green flesh grew a brown layer that was not there before.
A new substance formed, so the browning is a chemical change.
Feedback per option
- A The pale green flesh grew a brown layer that was not there before: a new substance formed.
- B The brown layer has properties the green flesh did not have; it is a new substance.
Pale, runny pancake batter turns golden brown and spongy on a hot griddle. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
The pale, runny batter became a golden, spongy solid.
A new substance with new properties formed, so cooking the pancake is a chemical change.
Feedback per option
- A Golden, spongy pancake has properties the runny batter did not have: a new substance formed.
- B The batter did not only change shape; it became a spongy solid with new properties.
A cardboard box is flattened for recycling. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
The flattened box is still cardboard.
No new substance formed, so flattening is a physical change.
Feedback per option
- A The flat sheet is still cardboard; only the shape changed.
- B Flattening changes the shape only: the box is still cardboard.
Iron bends without breaking. The orange flakes on a rusted nail crumble. What does this difference tell you?
- A The flakes are iron rolled out into a thinner shape.
- B The flakes are a different substance from iron.
- C The flakes are iron that has cooled down.
Answer
Key: B — The flakes are a different substance from iron.
The flakes crumble instead.
A different property means a different substance, so the flakes are not iron.
Feedback per option
- A Thin iron still bends without breaking; the crumbling flakes are a different substance.
- B A different property means a different substance: the flakes are not iron.
- C Cold iron still bends without breaking; the crumbling flakes are a different substance.
Harper says: "Rust is just iron with some oxygen stuck on top, so the flakes are still iron." Is Harper correct?
- A yes
- B no
Answer
Key: B — no
In rust the iron atoms are joined to oxygen atoms in new particles.
New particles have new properties, so rust is a different substance and Harper is not correct.
Feedback per option
- A The oxygen is not stuck on top. Iron atoms joined with oxygen atoms into new particles with new properties, so rust is a different substance.
- B Iron atoms joined with oxygen atoms into new particles. The new particles have new properties, so rust is a different substance.
A change in which a new substance forms, with its own properties, is called a…
Typed answer
Answer
Accepted: chemical change · a chemical change · chemical
The new substance has its own properties, different from the substance you started with.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
The signs of a chemical change
MAT-064 · Name the signs of chemical change — Name the observable signs that a chemical change may have occurred.
Script
| Say | Screen |
|---|---|
| A spoon of baking soda goes into a beaker of vinegar, and it fizzes. | [a beaker of vinegar; the spoon tips in; it fizzes] |
| A match burns with a yellow flame and warms your fingers. | [a match flares] |
| A cut apple turns brown. | [an apple browns] |
| Two clear liquids poured together turn cloudy white. | [two liquids go cloudy] |
| What do these scenes have in common? | [the four scenes; question mark] |
| In each, a chemical change happened, and something you could notice changed. | [the four scenes ringed] |
| Nobody can see the atoms join, yet a cook, a mechanic and a doctor spot chemical changes every day. | [a magnifier over the beaker finds no atoms to watch; three people at work] |
| The apple turned brown: a color change. | [icon: color; label A COLOR CHANGE] |
| Bubbles poured off the vinegar: a gas forming. | [icon: gas; label A GAS FORMING] |
| A white solid appeared where two liquids met: a solid forming, called a precipitate. | [icon: solid; label A SOLID FORMING; chip: PRECIPITATE] |
| The match warmed your fingers: a temperature change. | [icon: temperature; label A TEMPERATURE CHANGE] |
| And the match burned with a flame: light given out. | [icon: light; label LIGHT GIVEN OUT] |
| Boiling water bubbles too, and boiling is a physical change. | [a pan boils; label A CLUE, NOT PROOF] |
| So, five signs tell you a chemical change may have happened: a color change, a gas forming, a solid forming from two liquids, a temperature change, and light given out. | [the rule slide: five_signs, the five panels in a row; nothing else printed] |
| Each sign is a clue, not proof: each can appear without a chemical change. | [the boiling pan beside the five panels] |
| So the cook, the mechanic and the doctor watch for these five signs, then check for a new substance. | [the three people; the five icons] |
| Okay, now your turn. | [the five labeled panels hold; no closing line and no bullets: the five panel labels are the summary] |
“Okay, now your turn.” — the attached question
A match burns with a yellow flame and warms your fingers. Which two signs of a chemical change are these?
- A a color change and a gas forming as bubbles
- B a temperature change and light given out
- C a solid forming (a precipitate) and a color change
Answer
Key: B — a temperature change and light given out
The match burns with a yellow flame: light given out.
Feedback per option
- A The match warms your fingers and burns with a flame: a temperature change and light.
- B The flame warms your fingers, a temperature change, and gives out light.
- C No solid forms; the match warms your fingers and gives out light.
Quiz after the video — the mastery check, 13 items
Which of these changes forms a new substance?
- A a damp steel scouring pad turning orange and crumbly
- B a spoonful of strawberry jam dissolving in a mug of hot tea
- C a wooden plank sawn in half
Answer
Key: A — a damp steel scouring pad turning orange and crumbly
The orange, crumbly patches have properties the gray steel did not have, so they are a new substance.
Dissolving and sawing leave the same substance, only spread out or in pieces.
Feedback per option
- A Steel is gray and firm; the orange, crumbly patches are a new substance with new properties.
- B The jam is still there, spread through the tea; no new substance formed.
- C Each half is still the same wood; no new substance formed.
What is a precipitate?
- A a solid that forms when two liquids meet
- B a gas that forms and bubbles up out of a liquid
- C a liquid that turns a new color
Answer
Key: A — a solid that forms when two liquids meet
That solid is called a precipitate.
A gas forming and a color change are two other signs.
Feedback per option
- A A precipitate is the solid that forms when two liquids meet.
- B A gas bubbling out of a liquid is the sign a gas forming, not a precipitate.
- C A liquid turning a new color is the sign a color change, not a precipitate.
Bubbles or fizz in a liquid show which of the five signs?
Typed answer
Answer
Accepted: a gas forming · gas forming · a gas forms · gas forms · a gas · gas · a gas is forming · gas is forming · a gas given off · gas given off · a gas being given off
So the sign is a gas forming.
Which of these is NOT one of the five signs that a chemical change may have happened?
- A the mixture gets warm on its own
- B a solid forms where two clear liquids meet and mix
- C the liquid is poured into a taller glass
Answer
Key: C — the liquid is poured into a taller glass
Getting warm on its own and a solid forming are on the list.
Pouring a liquid into a new glass is not.
Feedback per option
- A A temperature change is one of the five signs.
- B A solid forming from two liquids, a precipitate, is one of the five signs.
- C Pouring changes the shape of the liquid; it is not one of the five signs.
Which of these is one of the five signs that a chemical change may have happened?
- A the liquid is stirred faster
- B light is given out
- C the substance is cut into smaller pieces
Answer
Key: B — light is given out
Light given out is on the list.
Stirring and cutting are things you do, not signs.
Feedback per option
- A Stirring is something you do to a mixture, not one of the five signs.
- B Light given out is one of the five signs.
- C Cutting makes smaller pieces of the same substance; it is not one of the five signs.
A clear liquid turns deep blue when a drop of a second liquid is added. Is this one of the five signs?
- A yes
- B no
Answer
Key: A — yes
That is a color change.
A color change is one of the five signs: yes.
Feedback per option
- A A color change is one of the five signs.
- B The liquid changed color, and a color change is one of the five signs.
A mixture in a cup gets warm on its own, with no heater near it. Is this one of the five signs?
- A yes
- B no
Answer
Key: A — yes
That is a temperature change.
A temperature change is one of the five signs: yes.
Feedback per option
- A A temperature change on its own is one of the five signs.
- B The mixture warmed with no heater, and a temperature change is one of the five signs.
A pan of soup on a hot stove gets warm. Is this one of the five signs?
- A yes
- B no
Answer
Key: B — no
The sign is a temperature change on its own, with nothing heating or cooling the mixture.
Warming from a stove is not one of the five signs: no.
Feedback per option
- A The soup got warm because the stove heated it. The sign is a temperature change on its own, with nothing heating or cooling the mixture.
- B The stove warmed the soup, so the warming is not one of the five signs. The sign is a temperature change on its own.
A spoon of honey stirred into warm milk vanishes. Is this one of the five signs?
- A yes
- B no
Answer
Key: B — no
Nothing changed color, no gas or solid formed, nothing warmed on its own or glowed.
Dissolving is not one of the five signs: no.
Feedback per option
- A Vanishing is dissolving, not one of the five signs. Nothing changed color, no gas or solid formed, nothing warmed on its own or glowed.
- B The honey dissolved and spread through the milk; nothing changed color, no gas or solid formed, nothing warmed on its own or glowed.
Yellow grains settle out where two clear liquids were mixed. Is this one of the five signs?
- A yes
- B no
Answer
Key: A — yes
A solid forming when two liquids meet is a precipitate.
A precipitate is one of the five signs: yes.
Feedback per option
- A A solid forming where two liquids meet, a precipitate, is one of the five signs.
- B The yellow grains are a solid that formed where two liquids met: a precipitate, one of the five signs.
An ice cube in a glass melts into a puddle. Is this one of the five signs?
- A yes
- B no
Answer
Key: B — no
Nothing changed color, no gas or solid formed, nothing warmed on its own or glowed.
A change of state is not one of the five signs: no.
Feedback per option
- A Melting is a change of state, not one of the five signs. Nothing changed color, no gas or solid formed, nothing warmed on its own or glowed.
- B Melting is a change of state; nothing changed color, no gas or solid formed, nothing warmed on its own or glowed.
Kofi says: "If bubbles appear in a liquid, a chemical change has definitely happened." Is Kofi correct?
- A yes
- B no
Answer
Key: B — no
Each sign is a clue, not proof, because each can appear without a chemical change.
Boiling water bubbles, and boiling is a physical change, so Kofi is not correct.
Feedback per option
- A Bubbles are a clue, not proof: water boiling in a pan bubbles, and boiling is a physical change.
- B Each sign is a clue, not proof. Boiling water bubbles, and boiling is a physical change.
Two clear liquids meet, and a white solid appears where they mix. What is that solid called?
Typed answer
Answer
Accepted: precipitate · a precipitate · the precipitate
It is one of the five signs that a chemical change may have happened.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Which sign is this?
MAT-064b · Apply the signs of chemical change to examples — Identify which sign of chemical change appears in a described reaction.
Script
| Say | Screen |
|---|---|
| Read these four sentences. | [four sentences appear one by one, printed as written: they are the data the lesson reads, not a caption] |
| A tablet dropped into water fizzes. | [sentence one highlighted] |
| A pale green leaf turns brown. | [sentence two] |
| The mixture in the beaker gets warm on its own. | [sentence three] |
| Two clear liquids poured together turn cloudy white. | [sentence four] |
| Each sentence shows one sign of a chemical change. Which sign is which? | [question mark] |
| Look for the word that tells what was seen. | [the telling words glow: fizzes, brown, warm, cloudy] |
| Fizzes: bubbles of gas left the water, so the sign is a gas forming. | [icon: gas; label A GAS FORMING] |
| Turns brown: the leaf's color changed, so the sign is a color change. | [icon: color; label A COLOR CHANGE] |
| The mixture gets warm on its own, so the sign is a temperature change. | [icon: temperature; label A TEMPERATURE CHANGE] |
| Turns cloudy white: a solid formed where two liquids met, so the sign is a solid forming, a precipitate. | [icon: solid; label A SOLID FORMING] |
| Some scenes show two signs at once: a log burning in a fireplace glows, and the room gets warmer. | [a fireplace; icons light and temperature] |
| So, to match a described change to its sign, look for the word that tells what was seen. | [the rule slide: sign_words_table; nothing else printed] |
| So the four sentences show a gas forming, a color change, a temperature change and a solid forming. | [four_scenes_l04] |
| Okay, now your turn. | [closing screen: one line — "To match a described change to its sign, look for the word that tells what was seen."] |
“Okay, now your turn.” — the attached question
A tablet dropped into water fizzes. Which sign of a chemical change is that?
- A a gas forming
- B a color change
- C light given out
Answer
Key: A — a gas forming
Bubbles or fizz mean a gas formed.
So the sign is a gas forming.
Feedback per option
- A Fizz is bubbles of gas leaving the water: a gas forming.
- B Fizz is about bubbles, not about color.
- C Fizz is about bubbles, not about light.
Quiz after the video — the mastery check, 11 items
Which sign of a chemical change is a precipitate?
- A a gas forming, seen as bubbles or fizz
- B a color change to a new color
- C a solid forming when two liquids meet
Answer
Key: C — a solid forming when two liquids meet
So the sign a precipitate belongs to is a solid forming.
Feedback per option
- A A gas forming shows as bubbles or fizz; a precipitate is a solid.
- B A color change is a new color; a precipitate is a solid that forms.
- C A precipitate is the solid that forms when two liquids meet.
A pool test strip dipped into the water turns from yellow to pink. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: A — a color change
Turns a new color means a color change.
So the sign is a color change.
Feedback per option
- A Turns from yellow to pink: a new color, so a color change.
- B No bubbles or fizz are described.
- C No solid appeared; the strip changed color.
- D Nothing got warmer or colder.
- E Nothing glowed or flashed.
Yeast stirred into warm sugar water froths with tiny bubbles. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: B — a gas forming
Bubbles or froth mean a gas formed.
So the sign is a gas forming.
Feedback per option
- A No new color is described.
- B Froths with bubbles: a gas formed and left the water.
- C No solid formed; bubbles are a gas.
- D The water was already warm; no temperature change is described.
- E Nothing glowed or flashed.
A glow stick is snapped, and it shines green. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: E — light given out
A glow, a flame or a shine means light was given out.
So the sign is light given out.
Feedback per option
- A Shining green is light, not a change of the stick's color.
- B No bubbles or fizz are described.
- C No solid formed.
- D Nothing got warmer or colder.
- E Shines green: light is given out.
Two clear liquids are poured together, and yellow grains settle to the bottom. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: C — a solid forming
A solid appearing where two liquids met means a precipitate formed.
So the sign is a solid forming.
Feedback per option
- A The grains are a solid that formed, not a liquid changing color.
- B Grains that settle are a solid, not a gas.
- C Grains settling out where two liquids met: a solid formed, a precipitate.
- D Nothing got warmer or colder.
- E Nothing glowed or flashed.
A hand-warmer packet is opened, and it gets hot in your hand. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: D — a temperature change
Warm or cold on its own means a temperature change.
So the sign is a temperature change.
Feedback per option
- A No new color is described.
- B No bubbles or fizz are described.
- C No solid formed.
- D Gets hot on its own: a temperature change.
- E Nothing glowed or flashed.
A drop of bleach on a red T-shirt turns the spot pale. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: A — a color change
Turns a new color means a color change.
So the sign is a color change.
Feedback per option
- A Turns pale: the red spot changed color.
- B No bubbles or fizz are described.
- C No solid formed.
- D Nothing got warmer or colder.
- E Nothing glowed or flashed.
Muffin batter puffs up in the oven as tiny bubbles form inside it. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: B — a gas forming
Bubbles mean a gas formed.
So the sign is a gas forming.
Feedback per option
- A No new color is described.
- B Tiny bubbles form: a gas formed inside the batter.
- C No solid formed from two liquids.
- D The oven heats the batter; the sentence describes bubbles, not a change on its own.
- E Nothing glowed or flashed.
A cold pack is squeezed: a powder inside dissolves in water, and the pack turns icy cold. Which sign is this?
- A a color change
- B a gas forming
- C a solid forming
- D a temperature change
- E light given out
Answer
Key: D — a temperature change
Warm or cold on its own means a temperature change.
So the sign is a temperature change, a clue: here the powder only dissolved.
Feedback per option
- A No new color is described.
- B No bubbles or fizz are described.
- C No solid formed.
- D Turns icy cold on its own: a temperature change. A clue only: the powder dissolved, and dissolving is a physical change.
- E Nothing glowed or flashed.
Charcoal in a grill gives out light, and the air above it gets hot. Which two signs appear?
- A a gas forming and a color change of the coals
- B a solid forming (a precipitate) and light given out
- C light given out and a temperature change
Answer
Key: C — light given out and a temperature change
Light given out is one of the five signs.
Hot on its own means a temperature change, so both signs appear.
Feedback per option
- A No bubbles or fizz are described, and no new color is described.
- B No solid formed from two liquids; the second sign is the hot air.
- C Gives out light is light given out; the air gets hot is a temperature change.
Two clear liquids are stirred together: the mixture turns cloudy white, and the cup gets warm. Which two signs appear?
- A a color change and a gas forming as bubbles
- B a solid forming and a temperature change
- C light given out and a gas forming as bubbles
Answer
Key: B — a solid forming and a temperature change
Cloudy means a solid formed where two liquids met: a precipitate.
Warm on its own means a temperature change, so both signs appear.
Feedback per option
- A Cloudy white is a solid forming where two liquids met, and no bubbles are described.
- B Turns cloudy white is a solid forming, a precipitate; the cup gets warm is a temperature change.
- C Nothing glowed, and no bubbles are described.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Physical or chemical? The one test
MAT-065 · Decide whether a change is physical or chemical — Classify a described change as physical or chemical by applying the new-substance test.
Script
| Say | Screen |
|---|---|
| Water boils in a kettle, and bubbles pour off it. | [the kettle bubbles] |
| Baking soda meets vinegar, and bubbles pour off that too. | [the beaker fizzes beside it] |
| One is a physical change and one is a chemical change. How can you tell which is which? | [question mark between them] |
| Bubbles are a clue, not proof, so ask the question that decides: did a new substance form? | [chip: DID A NEW SUBSTANCE FORM?] |
| Inside the kettle's bubbles is water as a gas: the same water particles as in the liquid. | [two_beakers, left column: the before box, the after box] |
| No new substance formed, so boiling is a physical change. | [label PHYSICAL CHANGE under the left column] |
| Inside the vinegar's bubbles is carbon dioxide, and there was none in the vinegar or baking soda. | [right column: the before box, the after box] |
| A new substance formed, so the fizzing is a chemical change. | [label CHEMICAL CHANGE under the right column] |
| Whether the change can be undone is not the test. | [chip crossed out: CAN IT BE UNDONE?] |
| If you rip a newspaper in half, nobody can mend it. | [a newspaper rips] |
| Yet the pieces are still newspaper: a physical change. | [label STILL NEWSPAPER] |
| Wax melting is still wax, a physical change; wax burning to soot is a chemical change. | [trap_pairs_table, first two rows] |
| So, to decide whether a change is physical or chemical, ask one question: did a new substance form? | [the rule slide: the two columns with their labels; chip DID A NEW SUBSTANCE FORM?; nothing else printed] |
| So the kettle's water bubbles are a physical change, and the vinegar's carbon dioxide bubbles are a chemical change. | [the two columns with their labels] |
| Okay, now your turn. | [closing screen: one line — "To decide whether a change is physical or chemical, ask one question: did a new substance form?"] |
“Okay, now your turn.” — the attached question
Water boils in a kettle. What is inside the bubbles?
- A carbon dioxide, a new gas
- B air that was trapped inside the water
- C water as a gas, the same particles
Answer
Key: C — water as a gas, the same particles
Those are the same water particles that were in the liquid.
No new substance formed, so boiling is a physical change.
Feedback per option
- A Carbon dioxide is in fizzing vinegar's bubbles, not a kettle's.
- B The kettle's bubbles are water as a gas, not trapped air.
- C The kettle's bubbles are water as a gas: the same water particles as in the liquid.
Quiz after the video — the mastery check, 14 items
In which kind of change does a new substance form?
- A physical change
- B chemical change
Answer
Key: B — chemical change
A chemical change is a change in which a new substance forms.
Feedback per option
- A In a physical change no new substance forms; the particles are the same particles.
- B A chemical change is a change in which a new substance forms.
Bubbles appear in a liquid. Do the bubbles alone prove that a chemical change happened?
- A yes
- B no
Answer
Key: B — no
Each sign is a clue, not proof, because each can appear without a chemical change.
So bubbles alone do not prove a chemical change.
Feedback per option
- A Bubbles alone are not proof. Boiling water bubbles, and boiling is a physical change.
- B A gas forming is a clue, not proof: boiling water bubbles, and boiling is a physical change.
Two clear liquids are poured together. Yellow grains form and settle to the bottom. Is the yellow solid a new substance?
- A yes
- B no
Answer
Key: A — yes
The grains are yellow and solid: properties neither liquid had.
So the yellow solid is a new substance: yes.
Feedback per option
- A Neither liquid was yellow or a solid; the grains have properties neither liquid had, so they are a new substance.
- B Both liquids were clear and runny; a yellow solid has properties neither had, so it is a new substance.
Two clear liquids are poured together, and yellow grains form and settle. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
The yellow grains are a solid that neither clear liquid was.
A new substance formed, so this is a chemical change.
Feedback per option
- A A yellow solid that neither clear liquid was is a new substance, so this is not a physical change.
- B A new substance, the yellow solid, formed, so this is a chemical change.
A slice of bread is cut into four squares. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
Each square is still bread.
No new substance formed, so cutting is a physical change.
Feedback per option
- A Each square is still bread; only the size and shape changed.
- B Cutting makes pieces of the same substance: each square is still bread.
A slice of bread left in the toaster turns black and gives off smoke. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
The soft bread became black crust and smoke.
New substances formed, so burning the toast is a chemical change.
Feedback per option
- A Black, brittle crust and smoke are substances the soft bread was not: a new substance formed.
- B The bread became black crust and smoke, substances with properties bread does not have.
A seashell dropped into a sour cleaning liquid fizzes. The gas in the bubbles is carbon dioxide, and neither the shell nor the liquid is carbon dioxide. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
Neither the shell nor the liquid is carbon dioxide, yet the bubbles are carbon dioxide.
A new substance formed, so the fizzing is a chemical change.
Feedback per option
- A Carbon dioxide formed where there was none: a new substance, so this is not a physical change.
- B Carbon dioxide formed where there was none: a new substance, so a chemical change.
A seashell is ground into a fine white powder. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
The powder is the shell in tiny pieces.
No new substance formed, so grinding is a physical change.
Feedback per option
- A The powder is still seashell in tiny pieces; only the size changed.
- B Grinding makes tiny pieces of the same substance: the powder is still seashell.
A pear is sliced into eight pieces. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
Each piece is still pear.
No new substance formed, so slicing is a physical change.
Feedback per option
- A Each piece is still pear; only the size and shape changed.
- B Slicing makes pieces of the same substance: each piece is still pear.
The pear slices turn brown after an hour on the plate. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
The pale flesh grew a brown layer that was not there before.
A new substance formed, so the browning is a chemical change.
Feedback per option
- A A brown layer that was not there before formed on the pale flesh: a new substance.
- B The brown layer has properties the pale flesh did not have: a new substance formed.
Each size and shade of circle is a different kind of atom; touching circles are joined. The left box shows the particles before a change; the right box shows a sample of what is left after it. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: B — chemical change
After, every particle is one large open circle joined to two small dark circles: a shape that was not there.
A new substance formed, so this is a chemical change.
Feedback per option
- A Before, two kinds of pair sat apart; after, every particle is a new shape, so the substance is new.
- B Every particle after is one large open circle joined to two small dark circles: a shape that was not there before, so a new substance.
Each size and shade of circle is a different kind of atom; touching circles are joined. The boxes show the particles before and after a change. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
After, every particle is the same pair, only laid out differently.
No new substance formed, so this is a physical change.
Feedback per option
- A Every particle after is the same pair of large open circles as before, only laid out differently.
- B Compare the shapes: the same pairs before and after, so no new substance formed.
Esme says: "Ripping a sheet of newspaper in half is a chemical change, because you can never undo it." Is Esme correct?
- A yes
- B no
Answer
Key: B — no
The ripped pieces are still newspaper, so no new substance formed.
Whether the change can be undone is not the test, so Esme is not correct.
Feedback per option
- A Whether a change can be undone is not the test. The pieces are still newspaper, so no new substance formed: a physical change.
- B The pieces are still newspaper, so no new substance formed: a physical change. Whether it can be undone is not the test.
Rosa says: "Grinding coffee beans into powder is a physical change, because the powder is still coffee." Is Rosa correct?
- A yes
- B no
Answer
Key: A — yes
The ground powder is the coffee beans in tiny pieces: the same substance.
No new substance formed, so grinding is a physical change and Rosa is correct.
Feedback per option
- A The powder is the beans in tiny pieces: the same substance, so no new substance formed.
- B Grinding changes size, not substance. The powder is the beans in tiny pieces, so no new substance formed: a physical change.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Show your evidence
MAT-065b · Justify the classification of a change — Cite the evidence from a described change that shows whether it is physical or chemical.
Script
| Say | Screen |
|---|---|
| A test asks: is frying an egg physical or chemical? Explain. | [a test page with the question] |
| A student writes chemical and stops. | [the word chemical, then a blank] |
| That earns half the points; the evidence earns the rest. What does a full answer say? | [half the points; question mark] |
| A full answer has three lines. | [three empty lines] |
| Line one says what you observed. | [label I OBSERVED…] |
| Line two says what that shows about whether a new substance formed. | [label THAT SHOWS…] |
| Line three names the change. | [label SO THE CHANGE IS…] |
| For the egg: I observed the clear, runny white turn white and solid. | [frame_cards, card one, line one fills] |
| That shows a new substance formed: the solid has properties the runny white did not. | [line two fills] |
| So the change is a chemical change. | [line three fills] |
| For a physical change, the evidence is that the substance is still there. Now consider a melting ice cube: I observed that the liquid looks, pours and tastes like water. | [card two: the ice cube melting; lines one and two fill] |
| It is still water, so no new substance formed, and the change is a physical change. | [card two, line three] |
| 'It cannot be undone' is not the test; 'it fizzed' counts only if something fizzed. | [two crossed-out answers] |
| So, to justify the call, say what you observed, say what it shows about a new substance, then name the change. | [the rule slide: the three cards; nothing else printed] |
| So on the test, the egg white turned solid, so a new substance formed: a chemical change. | [the test page, three lines written] |
| Okay, now your turn. | [closing screen: bullets — • I observed… (what you saw) • That shows… (whether a new substance formed) • So the change is… (name it)] |
“Okay, now your turn.” — the attached question
A full answer to 'Is this change physical or chemical? Explain.' has three lines. What does the first line say?
- A the name of the change
- B what the student observed
- C whether the change can be undone
Answer
Key: B — what the student observed
Line two says what that shows about a new substance.
Line three names the change.
Feedback per option
- A The name of the change is line three.
- B Line one says what you observed.
- C Whether a change can be undone is not the test, and it is not one of the three lines.
Quiz after the video — the mastery check, 13 items
Which question decides whether a change is physical or chemical?
- A Can the change be undone afterwards?
- B Did a new substance form?
- C Did bubbles appear?
Answer
Key: B — Did a new substance form?
One question decides: did a new substance form?
Feedback per option
- A Whether a change can be undone is not the test.
- B The one test is whether a new substance formed.
- C Bubbles are a clue, not proof; the test is whether a new substance formed.
Two clear liquids meet, the mixture goes cloudy, and grains settle. Which sign is this?
- A a gas forming, seen as bubbles or fizz
- B a color change to a new color
- C a solid forming
Answer
Key: C — a solid forming
A solid appearing where two liquids met means a precipitate formed.
So the sign is a solid forming.
Feedback per option
- A Grains that settle are a solid, not a gas.
- B Cloudy with grains settling is a solid forming, not only a new color.
- C A solid appearing where two liquids met is a solid forming: a precipitate.
Pale, runny cake batter is baked into a brown, spongy cake. Which observation is the evidence?
- A The runny batter turned into a brown, spongy solid.
- B The oven was set to a high temperature for the whole bake.
- C The cake was baked for exactly 30 minutes.
Answer
Key: A — The runny batter turned into a brown, spongy solid.
The batter was pale and runny; it became brown, spongy and solid.
That change in the substance is the observation to cite.
Feedback per option
- A What the batter became is the observation that tells you about a new substance.
- B The oven setting is what was done, not what the batter became.
- C The time is what was done, not what the batter became.
Pale, runny cake batter baked into a brown, spongy cake. What does that observation show?
- A The batter is still batter, in a new shape.
- B A new substance formed.
- C The change can be undone by cooling the cake.
Answer
Key: B — A new substance formed.
Those are properties the batter did not have.
So a new substance formed.
Feedback per option
- A Spongy, brown and solid are properties the runny batter did not have, so it is not the same substance.
- B The cake has properties the batter did not have, so a new substance formed.
- C Whether a change can be undone is not the test.
Pale, runny cake batter baked into a brown, spongy cake. Which kind of change is baking the cake?
- A physical change
- B chemical change
Answer
Key: B — chemical change
That shows a new substance formed.
So baking the cake is a chemical change.
Feedback per option
- A A new substance with new properties formed, so this is not a physical change.
- B A new substance formed, so baking the cake is a chemical change.
A glass rod is heated until it softens, bent into a hook, and cooled: it is still clear, hard glass. What does that observation show?
- A A new substance formed.
- B A new substance formed, then turned back into glass.
- C No new substance formed.
Answer
Key: C — No new substance formed.
The substance is still glass.
So no new substance formed.
Feedback per option
- A Still clear and hard means the hook has the properties glass has; nothing new formed.
- B The hook is clear, hard glass all through; nothing new formed and nothing turned back. Whether a change can be undone is not the test.
- C The hook is still clear, hard glass, so the substance is still there and nothing new formed.
A glass rod is heated, bent into a hook and cooled, and the hook is still clear, hard glass. Which kind of change is this?
- A physical change
- B chemical change
Answer
Key: A — physical change
That shows no new substance formed.
So bending the rod is a physical change.
Feedback per option
- A The glass is still glass, only in a new shape: no new substance formed.
- B No new substance formed; the hook is still clear, hard glass, so this is not a chemical change.
Steel wool is shiny, and its strands bend without breaking. Held in a flame, it glows, and a black, crumbly powder is left that does not shine and does not bend. Justify whether this is a physical or a chemical change.
Starter: I observed…
Answer
Model answer · ['the observation: shiny steel wool became a black, crumbly powder that does not shine or bend', 'what it shows: a new substance formed (new properties)', 'the call: a chemical change'] points
That shows a new substance formed, because the powder has properties the steel wool did not have.
So the change is a chemical change.
A bar of soap is carved into the shape of a swan. The swan and the shavings both smell, feel and lather like the soap. Justify whether this is a physical or a chemical change.
Starter: I observed…
Answer
Model answer · ['the observation: the swan and shavings still smell, feel and lather like the soap', 'what it shows: the soap is still soap, no new substance formed', 'the call: a physical change'] points
That shows the soap is still soap, so no new substance formed.
So the change is a physical change.
A shiny brass doorknob turns dull brown over the years. The change is a chemical change. Which observation is the evidence for that call?
- A A dull brown layer that was not there before formed on the knob.
- B Brass doorknobs always change like this after many years in a busy house.
- C The knob cannot be made shiny again by wiping it.
- D The knob fizzed and gave off bubbles of gas.
Answer
Key: A — A dull brown layer that was not there before formed on the knob.
It says what that shows: a new substance formed.
Then it names the change: a chemical change.
Feedback per option
- A The brown layer has properties the shiny brass did not have, so a new substance formed: that is the evidence.
- B What usually happens to doorknobs is not an observation of this knob's substance.
- C Whether a change can be undone is not the test.
- D Nothing in the scene fizzed; this cites a sign that was not there.
Puddles of seawater in a tide pool dry up in the sun, leaving white salt behind. The change is a physical change. Which observation is the evidence for that call?
- A The water left the pool for good and can never be put back into it.
- B Water is a liquid, and liquids always do this.
- C The salt left behind is the salt that was dissolved in the seawater.
- D The pool got warm in the sun.
Answer
Key: C — The salt left behind is the salt that was dissolved in the seawater.
It says what that shows: the salt was there all along, dissolved, so no new substance formed.
Then it names the change: a physical change.
Feedback per option
- A Whether a change can be undone is not the test.
- B What liquids usually do is not an observation of this pool's substances.
- C The salt was there all along, dissolved, so no new substance formed: that is the evidence.
- D Warmth from the sun is not a change in the substances; the salt and the water are still salt and water.
A glow stick is snapped, the two liquids inside mix, and it glows green for hours. The change is a chemical change. Which observation is the evidence for that call?
- A Glow sticks are made in a factory so that they will glow when snapped.
- B Light came from the mixed liquids on their own.
- C The stick can never be made to glow again once it fades.
- D The stick changed shape when it was snapped.
Answer
Key: B — Light came from the mixed liquids on their own.
It says what that shows: light given out is a clue that new substances formed.
Then it names the change: a chemical change.
Feedback per option
- A How glow sticks are made is not an observation of the liquids' substances.
- B Light given out by the mixed liquids on their own is a clue that new substances formed: that is the evidence.
- C Whether a change can be undone is not the test.
- D A change of shape is not evidence of a new substance.
An ice sculpture melts into a puddle on a warm day. The change is a physical change. Which observation is the evidence for that call?
- A The ice can never be put back into the same sculpture once it has melted.
- B The sculpture was very cold to start with.
- C The ice gave off bubbles as it melted.
- D The puddle is water, the same substance as the ice.
Answer
Key: D — The puddle is water, the same substance as the ice.
It says what that shows: the ice was water too, so no new substance formed.
Then it names the change: a physical change.
Feedback per option
- A Whether a change can be undone is not the test.
- B How cold the sculpture was is not evidence about a new substance.
- C Nothing in the scene bubbled; this cites a sign that was not there.
- D The puddle is water and the ice was water, so no new substance formed: that is the evidence.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Summary: Physical and chemical change
Script, part 1 (129 words)
| Say | Screen |
|---|---|
| Here is everything we found out about physical and chemical change. | [a still: the torn paper and the rusted nail] |
| A physical change is a change in which no new substance forms. | [chip: PHYSICAL CHANGE; the paper, the ice, the sugar] |
| The size, the shape or the state changes, but the particles are the same particles, arranged or moving differently. | [ice_to_water: the same particles] |
| A chemical change is a change in which a new substance forms. | [chip: CHEMICAL CHANGE; the nail] |
| The new substance has its own properties, different from the substance you started with. | [iron_rust_table] |
| Five signs tell you a chemical change may have happened: a color change, a gas forming, a solid forming from two liquids, a temperature change, and light given out. | [five_signs] |
| A solid that forms when two liquids meet is called a precipitate. | [icon: solid; chip: PRECIPITATE] |
| And each sign is a clue, not proof, because each can appear without a chemical change. | [label A CLUE, NOT PROOF] |
| Okay, now your turn. | [closing screen: bullets — • Physical change: no new substance forms; the same particles, rearranged • Chemical change: a new substance forms, with its own properties • Five signs: a color change, a gas forming, a solid forming, a temperature change, light given out • Each sign is a clue, not proof] |
“Okay, now your turn.” — the check question between the parts
A cut apple turns brown. Which sign of a chemical change is that?
- A a color change
- B a gas forming
- C a temperature change
Answer
Key: A — a color change
Turning a new color is a color change.
Feedback per option
- A The apple turns a new color: a color change.
- B No bubbles form; the apple changes color.
- C The apple does not get warm or cold; it changes color.
Script, part 2 (89 words)
| Say | Screen |
|---|---|
| Here is everything we found out about telling the two changes apart. | [a still: two_beakers] |
| To match a described change to its sign, look for the word that tells what was seen. | [sign_words_table] |
| To decide whether a change is physical or chemical, ask one question: did a new substance form? | [chip: DID A NEW SUBSTANCE FORM?] |
| The signs are clues; the new-substance question decides. | [the two columns labeled] |
| And whether the change can be undone is not the test. | [chip crossed out: CAN IT BE UNDONE?] |
| To justify the call, say what you observed, say what it shows about a new substance, then name the change. | [frame_cards] |
| Okay, now your turn. | [closing screen: bullets — • Match a described change to its sign by the word that tells what was seen • The one question: did a new substance form? • Whether it can be undone is not the test • Justify: I observed… / that shows… / so the change is…] |
“Okay, now your turn.” — the two questions after part 2
Which one question decides whether a change is physical or chemical?
- A Did a new substance form?
- B Can the change be undone afterwards?
- C Did bubbles appear?
Answer
Key: A — Did a new substance form?
Whether a change can be undone is not the test.
One question decides: did a new substance form?
Feedback per option
- A The one question that decides is whether a new substance formed.
- B Whether a change can be undone is not the test.
- C Bubbles are a clue, not proof; the question that decides is whether a new substance formed.
Which of these is a chemical change?
- A ice melting to water
- B an iron nail rusting
- C a sheet of paper tearing
Answer
Key: B — an iron nail rusting
Rust is a new substance, not iron.
So rusting is a chemical change.
Feedback per option
- A Melted ice is still water: no new substance forms, so melting is a physical change.
- B Rust is a new substance with its own properties, so rusting is a chemical change.
- C Torn paper is still paper: no new substance forms, so tearing is a physical change.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Applied without asking
Rulings you have already given; in force on every card above, not re-asked.
- Every video ends “Okay, now your turn.” with one easy, video-dependent question (the XP gate).
- An intro video is at most 120 words and teaches nothing: it opens the question the topic answers.
- A summary video is at most 300 words: everything taught, in order, just before the PP100.
- A lesson script is at most 200 words.
- Each lesson ships as both a video and an article; the article is not under review here.
The topic’s fixed wording (the lexicon the scripts repeat)
- A physical change is a change in which no new substance forms.
- The size, the shape or the state changes, but the particles are the same particles, arranged or moving differently.
- A chemical change is a change in which a new substance forms.
- The new substance has its own properties, different from the substance you started with.
- Five signs tell you a chemical change may have happened: a color change, a gas forming, a solid forming from two liquids, a temperature change, and light given out.
- A solid that forms when two liquids meet is called a precipitate.
- Each sign is a clue, not proof, because each can appear without a chemical change.
- To decide whether a change is physical or chemical, ask one question: did a new substance form?
- Whether the change can be undone is not the test.
- To justify the call, say what you observed, say what it shows about a new substance, then name the change.
Scripts, questions and quizzes are read from the course content as it stands today; the student site for this topic is here.