Topic 13 · Water's special properties — 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, 4 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: Water's special properties
Script
| Say | Screen |
|---|---|
| Here is a pond on a rainy morning. | [a pond; rain] |
| A raindrop lands on a lily pad and sits there as a round bead, not a flat sheet. | [scene 1: the bead on the pad] |
| Water climbs up inside the reeds' narrow stems, above the pond. | [scene 2: the reed, the water level inside it above the pond's] |
| And a water strider, a thin insect with long legs, walks across the pond without sinking. | [scene 3: the strider on the surface] |
| The same water does all three. | [the three scenes in a row] |
| So what is going on inside the water that lets it bead, climb and hold up an insect? | [question mark over the pond] |
| To find out, we will look at what is going on between the particles of water, and between water and other things. | [the three scenes stay] |
| Okay, so are you ready to find out what lets a water strider walk on a pond? | [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 out what lets a water strider walk on a pond?
- A Yes, let's go! — Great. Here we go.
- B Not sure yet — That's fine. We take it one step 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
Water particles pull on each other
MAT-073 · Cohesion — Explain why water forms rounded droplets by referring to the attraction between water particles.
Script
| Say | Screen |
|---|---|
| Suppose you drip water onto a penny, one drop at a time. | [a dropper over a penny seen from the side; drops land] |
| The water does not run off; it piles into a rounded dome. | [the dome rises and rounds with each drop] |
| The penny holds 25 drops before the dome spills. What holds the water together? | [a counter reaches 25; question mark over the dome] |
| The water's own particles hold it together. | [the dome; chip: ITS OWN PARTICLES] |
| Water is made of tiny particles, packed close and touching. | [zoom into the dome: a heap of touching gray circles] |
| Every water particle pulls on the particles next to it. | [double-headed arrows appear between neighboring circles] |
| This double-headed arrow means the two particles pull on each other, not that they move. | [the key: two circles, the arrow, the words a pull, not a movement] |
| An outer particle has neighbors only on its inner side, so it is pulled in toward the rest. | [arrows on the outer circles, each pointing inward] |
| Water pulling on water is one substance pulling on itself. | [label: water on water] |
| The pull between particles of the same substance is called cohesion. | [chip: COHESION] |
| A raindrop on a leaf sits as a rounded bead, not a flat sheet. | [a bead on a leaf beside a dashed flat sheet, crossed out] |
| When two drops touch, they join into one bigger drop. | [before and after: two drops, then one] |
| So, here's what we've seen. Water particles pull on each other. | [the rule slide: the dome zoom with its inward arrows; chip COHESION; nothing else printed] |
| Cohesion pulls the outer particles of a drop in toward the rest, so the water gathers into a rounded shape. | [the heap rounds into a dome] |
| So on the penny, cohesion pulls the outer particles in, and the water stands as a dome. | [the penny and its dome] |
| Okay, now your turn. | [closing screen: bullets — • Water particles pull on each other • This pull is cohesion] |
“Okay, now your turn.” — the attached question
Water is dripped onto a penny and piles into a rounded dome. What does cohesion do to the water?
- A It pulls it together into a dome.
- B It pushes it off the edge.
- C It turns it into water vapor.
Answer
Key: A — It pulls it together into a dome.
Cohesion pulls the water's outer particles in toward the rest.
So the water on the penny stands as a rounded dome.
Feedback per option
- A Cohesion pulls the outer particles in toward the rest, so the water stands as a dome.
- B Nothing pushes the water off the edge; cohesion pulls the water together.
- C The water stays liquid; cohesion pulls it together into a dome.
Quiz after the video — the mastery check, 10 items
A glass holds water. What is the water made of?
- A tiny particles, packed close and touching
- B one smooth stuff with nothing smaller inside it
- C tiny particles, far apart with empty space between them
Answer
Key: A — tiny particles, packed close and touching
Water in a glass is a liquid.
In a liquid the particles are packed close and touching, with no fixed positions.
Feedback per option
- A Water is a liquid, so its particles are packed close and touching, with no fixed positions.
- B All matter is made of tiny particles, water included.
- C Particles far apart, with empty space between them, make a gas.
In liquid water the particles touch.
Water particles pull on other water particles. What is this pull, between particles of the same substance, called?
Typed answer
Answer
Accepted: cohesion · the cohesion
Water pulling on water is cohesion.
What does cohesion mean?
- A water particles spreading out to fill a space
- B water particles pulling on each other
- C water particles turning into water vapor
Answer
Key: B — water particles pulling on each other
The pull between particles of the same substance is called cohesion.
So cohesion means water particles pulling on each other.
Feedback per option
- A Spreading out to fill a space is what a gas does; cohesion is a pull.
- B Cohesion is the pull between particles of the same substance, such as water on water.
- C Turning into vapor is evaporating; cohesion is a pull between particles.
A drop of water lands on a smooth plastic lid. What shape does the water take?
- A a rounded bead
- B a flat sheet across the lid
Answer
Key: A — a rounded bead
The pull tugs the drop's outer particles in toward the rest.
So the water gathers into a rounded bead, not a flat sheet.
Feedback per option
- A Cohesion pulls the drop's outer particles in, so the drop gathers into a rounded bead.
- B The water's outer particles are pulled in toward the rest, so the water does not spread into a flat sheet.
In the morning, dew stands on the hood of a car as round beads. Explain why each bead is round instead of spread out flat.
Starter: Water particles…
Answer
Model answer · ['water particles pull on each other (cohesion)', 'the outer particles are pulled in toward the rest', 'so the water gathers into a rounded shape'] points
This pull is cohesion.
Cohesion tugs each bead's outer particles in toward the rest.
So the water gathers into the roundest shape it can, a bead.
Idris says: "The water on the penny piles up into a dome because the penny pushes the water up." Is Idris correct?
- A yes
- B no
Answer
Key: B — no
Cohesion pulls the outer particles in toward the rest, so the water gathers into a dome.
The penny only holds the water up; it does not gather the water into a dome, so Idris is not correct.
Feedback per option
- A The penny holds the water up, but it does not gather it into a dome.
The water particles pull each other in, so the water gathers into a dome. - B The water particles pull each other in, so the water gathers into a dome.
The penny only holds the water up.
Does cohesion pull the outer particles of a drop in, toward the rest of the water?
- A yes
- B no
Answer
Key: A — yes
An outer particle has neighbors only on its inner side.
So cohesion pulls the outer particle in, toward the rest.
Feedback per option
- A Cohesion pulls the outer particles in toward the rest; that is what rounds the drop.
- B Cohesion is a pull toward the rest of the water, so the outer particles are pulled in.
Does cohesion push water particles apart from each other?
- A yes
- B no
Answer
Key: B — no
That pull is cohesion.
A pull draws particles together, so cohesion does not push them apart.
Feedback per option
- A Cohesion is a pull, not a push: water particles pull on each other.
- B Cohesion is a pull between water particles; nothing pushes them apart.
Two small drops of water on a plate are pushed until they touch. What happens?
- A they push each other apart
- B they stay as two touching drops
- C they join into one bigger drop
Answer
Key: C — they join into one bigger drop
When the drops touch, the particles of one drop pull on the particles of the other.
So the two drops join into one bigger drop.
Feedback per option
- A Water particles pull on each other; they do not push apart.
- B The particles of one drop pull on the particles of the other, so the drops do not stay separate.
- C The particles of one drop pull on the particles of the other, so the two drops join into one.
After rain, beads of water hang on the threads of a spider's web. Why is each bead rounded?
- A the thread squeezes the water into a ball
- B the water particles pull on each other
- C the air presses the water into a ball
Answer
Key: B — the water particles pull on each other
Cohesion pulls each bead's outer particles in toward the rest.
So each bead gathers into a rounded shape.
Feedback per option
- A A thread holds the bead in place; it does not squeeze the water.
- B Cohesion pulls each bead's outer particles in toward the rest, so the bead is rounded.
- C The air does not shape the bead; the water's own particles pull each other in.
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
Water pulls on other surfaces too
MAT-074 · Adhesion — Distinguish cohesion from adhesion by identifying which involves attraction between the same substance and which involves different substances.
Script
| Say | Screen |
|---|---|
| Suppose you dip the corner of a paper towel into a glass of water. | [a glass; a towel strip dips in] |
| The water climbs up the towel, above the water in the glass. | [the wet part rises above the level] |
| When you tip the glass and pour the water out, a thin film stays stuck inside. | [the glass tips, empties, and stands again with a film on its inside] |
| Cohesion pulls water toward water; what pulls water toward paper and glass? | [question mark between the towel and the glass] |
| The paper's particles and the glass's particles do. | [zoom on the towel: gray circles beside a hatched band labeled paper; pull arrows to the band] |
| That pull drags the water's edge up the towel. | [the edge climbs] |
| In the glass, water pulls on glass, so a film stays stuck. | [gray circles pulled to a hatched band labeled glass] |
| Water pulling on paper or glass is two different substances pulling on each other. | [label: water on paper; water on glass] |
| The pull between particles of different substances is called adhesion. | [chip: ADHESION] |
| Cohesion is water pulling on water; adhesion is water pulling on something else. | [the two-panel figure: water on water, water on glass] |
| To sort a case, ask what is pulling on what. | [chip: WHAT PULLS ON WHAT?] |
| A drop beading on a leaf is water on water, so it is cohesion; water climbing a towel is water on paper, so it is adhesion. | [tick over the bead; cross over the towel; chip above: SAME SUBSTANCE?] |
| So, here's what we've seen. Water particles also pull on the particles of other substances, such as glass and paper. | [the rule slide: the five cases under the question; chips COHESION, ADHESION; nothing else printed] |
| The pull between particles of different substances is called adhesion. | [chip ADHESION brightens] |
| Okay, now your turn. | [closing screen: bullets — • Water particles also pull on other substances, such as glass and paper • This pull is adhesion] |
“Okay, now your turn.” — the attached question
The corner of a paper towel dips into water, and the water climbs up the towel. Which two things pull on each other?
- A water and water
- B water and glass
- C water and paper
Answer
Key: C — water and paper
Water and paper are two different substances.
That pull, adhesion, drags the water's edge up the towel.
Feedback per option
- A Water pulling on water is cohesion; the climb comes from the water pulling on the paper.
- B The glass holds the water; the climb up the towel is the water pulling on the paper.
- C The water particles pull on the particles of the paper: two different substances, adhesion.
Quiz after the video — the mastery check, 12 items
A drop of water pulls itself into a rounded shape. What is the pull between water particles and other water particles called?
Typed answer
Answer
Accepted: cohesion · the cohesion
The pull between particles of the same substance is called cohesion.
Water particles pull on the particles of glass. What is this pull, between particles of two different substances, called?
Typed answer
Answer
Accepted: adhesion · the adhesion
Water pulling on glass is adhesion.
What does adhesion mean?
- A water pulling on a different substance
- B water pulling on more water
- C water spreading out to fill its container
Answer
Key: A — water pulling on a different substance
The pull between particles of different substances is called adhesion.
So adhesion means water pulling on a different substance.
Feedback per option
- A Adhesion is the pull between particles of different substances, such as water on glass.
- B Water pulling on water is the same substance: that is cohesion.
- C Spreading out to fill a container is what a gas does; adhesion is a pull between particles.
A drop of water on a tabletop stands as a rounded bead. Which pull is this?
- A cohesion
- B adhesion
Answer
Key: A — cohesion
The drop's water particles pull on each other: water on water.
The same substance pulling on itself is cohesion.
Feedback per option
- A Water pulls on water: the same substance, so cohesion.
- B The bead is water pulling on water, the same substance; adhesion needs two different substances.
Water soaks up into a dry sponge set in a puddle. Which pull is this?
- A cohesion
- B adhesion
Answer
Key: B — adhesion
The water particles pull on the particles of the sponge: water on sponge.
Two different substances pulling on each other is adhesion.
Feedback per option
- A Water pulls on the sponge, a different substance; cohesion is water pulling on water.
- B Water pulls on the sponge: two different substances, so adhesion.
After rinsing, water clings to the bristles of a paintbrush. Which pull is this?
- A cohesion
- B adhesion
Answer
Key: B — adhesion
The water particles pull on the particles of the bristles: water on bristle.
Two different substances pulling on each other is adhesion.
Feedback per option
- A Water pulls on the bristles, a different substance; cohesion is water pulling on water.
- B Water pulls on the bristles: two different substances, so adhesion.
Two raindrops on the lid of a trash can run together into one bigger drop. Which pull is this?
- A cohesion
- B adhesion
Answer
Key: A — cohesion
The particles of one drop pull on the particles of the other: water on water.
The same substance pulling on itself is cohesion.
Feedback per option
- A The two drops' water particles pull on each other: water on water, so cohesion.
- B The joining is water pulling on water, the same substance; the lid is not part of that pull.
A thin stream of water from a faucet holds together as one rope as it falls. Which pull is this?
- A cohesion
- B adhesion
Answer
Key: A — cohesion
The water particles in the stream pull on each other: water on water.
The same substance pulling on itself is cohesion.
Feedback per option
- A The stream's water particles pull on each other: water on water, so cohesion.
- B Holding together is water pulling on water, the same substance; adhesion needs a different substance.
Gray circles are water particles, the hatched band is a glass wall, and the double-headed arrow shows a pull. Which pull does the arrow show?
- A cohesion
- B adhesion
Answer
Key: A — cohesion
The arrow joins two gray circles: two water particles.
Water on water is the same substance, so the pull is cohesion.
Feedback per option
- A The arrow joins two water particles: the same substance, so cohesion.
- B The arrow joins two gray circles, two water particles, not a particle and the glass.
Gray circles are water particles, the hatched band is a glass wall, and the double-headed arrow shows a pull. Which pull does the arrow show?
- A cohesion
- B adhesion
Answer
Key: B — adhesion
The arrow joins a gray circle, a water particle, to the hatched band, the glass.
Water on glass is two different substances, so the pull is adhesion.
Feedback per option
- A The arrow joins a water particle to the glass wall, not to another water particle.
- B The arrow joins a water particle to the glass wall: two different substances, so adhesion.
Rain clings to the underside of a metal railing instead of falling straight off. Which pull is this?
- A cohesion
- B adhesion
Answer
Key: B — adhesion
The water particles pull on the particles of the metal: water on metal.
Two different substances pulling on each other is adhesion.
Feedback per option
- A Water pulls on the metal, a different substance; cohesion is water pulling on water.
- B Water pulls on the metal railing: two different substances, so adhesion.
Malia says: "Water sticking to a window is cohesion, because the sticking thing is water." Is Malia correct?
- A yes
- B no
Answer
Key: B — no
The water particles pull on the particles of the glass: water on glass.
Two different substances pulling on each other is adhesion, so Malia is not correct.
Feedback per option
- A Being water is not the test; what pulls on what is. Water pulls on glass, two different substances, so it is adhesion.
- B Water and glass are two different substances, so water sticking to a window is adhesion. Cohesion is water pulling on water.
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 surface acts like a stretched skin
MAT-075 · Surface tension — Explain how surface tension allows small objects to rest on water without sinking.
Script
| Say | Screen |
|---|---|
| Suppose you drop a steel paper clip into water: it sinks. | [the clip falls to the bottom] |
| Steel has a density of about 8 grams per cubic centimeter, and water 1.0 gram per cubic centimeter, so steel is denser. | [the two-row density table] |
| Now suppose you lay a dry clip gently on the water: it rests, and the surface dips under it. | [the clip lowered; the surface line dips under it] |
| Why does the same clip sink one time and rest the next? | [question mark between the two glasses] |
| The water's surface holds it up. | [the resting clip; the dipped surface highlighted] |
| Steel is denser than water, so the resting clip is not floating. | [label: not floating] |
| Water particles pull on each other; that pull is cohesion. | [zoom: gray circles with pull arrows] |
| A particle inside has neighbors all around, so it is pulled from every side. | [particle P ringed; six arrows] |
| A particle at the surface has no water above it, so its neighbors pull it only sideways and down. | [particle S in the top row; four arrows, none upward] |
| So the surface particles hold together like a tight, stretched skin. | [arrows along the whole top row] |
| This skin effect is called surface tension. | [chip: SURFACE TENSION] |
| Laid on gently, the clip dips the skin without breaking it, so it rests. | [the sagging top row under the clip] |
| Dropped hard, the clip punches through the skin, and steel, denser than water, sinks. | [the clip breaks the row and falls] |
| So, here's what we've seen. The surface particles hold together like a tight, stretched skin. | [the rule slide: the skin zoom, the top row with its sideways-and-down arrows; chip SURFACE TENSION; nothing else printed] |
| This skin effect is called surface tension. | [chip SURFACE TENSION brightens] |
| Okay, now your turn. | [closing screen: bullets — • The surface particles hold together like a tight, stretched skin • This skin effect is surface tension] |
“Okay, now your turn.” — the attached question
A steel paper clip laid gently on water rests on the surface. What holds it up?
- A the clip being less dense than water
- B the water's surface skin
- C air bubbles under the clip
Answer
Key: B — the water's surface skin
So they hold together like a tight, stretched skin.
The clip does not break the skin, so the skin holds it up.
Feedback per option
- A Steel is denser than water, so the clip cannot float; the surface skin holds it up.
- B The surface particles hold together like a stretched skin, and the skin holds the clip up.
- C No air is trapped under the clip; the surface skin holds it up.
Quiz after the video — the mastery check, 12 items
Steel has a density of about 8 g/cm³ and water has a density of 1.0 g/cm³. A steel nut is dropped into a bucket of water. What does the nut do?
- A it sinks
- B it floats
Answer
Key: A — it sinks
Steel is denser than water.
An object denser than water sinks when it is dropped in, so the nut sinks.
Feedback per option
- A Steel is denser than water, so the nut sinks.
- B An object floats only if it is less dense than the water; steel at about 8 g/cm³ is denser than water at 1.0 g/cm³.
Which name is given to the pull between water particles and other water particles?
- A adhesion
- B cohesion
- C density
Answer
Key: B — cohesion
Water on water is the same substance.
The pull between particles of the same substance is called cohesion.
Feedback per option
- A Adhesion is the pull between water and a different substance.
- B The pull between particles of the same substance is called cohesion.
- C Density is how much mass a material packs into each cubic centimeter; it is not a pull.
The particles at the surface of water hold together like a tight, stretched skin. What is this skin effect called?
Typed answer
Answer
Accepted: surface tension · the surface tension
This skin effect is called surface tension.
What does surface tension mean?
- A the surface particles pull each other into a tight skin
- B the water at the surface is denser than the water below
- C the air presses down on the surface
Answer
Key: A — the surface particles pull each other into a tight skin
So the surface particles hold together like a tight, stretched skin.
This skin effect is called surface tension.
Feedback per option
- A The surface particles, pulled only sideways and down, hold together like a stretched skin: surface tension.
- B The surface water is the same water, with the same density; the skin comes from the pulls between its particles.
- C Air pressing down is not surface tension; the skin comes from the surface particles pulling on each other.
A dry sewing needle is lowered flat onto still water, very gently. What happens?
- A it sinks at once
- B it rests on top of the water
- C it floats half out of the water
Answer
Key: B — it rests on top of the water
A small object lowered gently does not break the skin.
So the needle rests on top of the water.
Feedback per option
- A The needle was lowered gently, so it does not break the skin.
The skin holds it up, so it does not sink. - B Lowered gently, the needle dips the surface skin but does not break it, so the skin holds the needle up.
- C The needle is not floating; the surface skin holds it up, lying on the surface.
A dry steel thumbtack is laid flat on still water, very gently, and it rests on top, although steel is denser than water. Explain why the thumbtack does not sink.
Starter: A particle at the surface…
Answer
Model answer · ['a surface particle is pulled only sideways and down (no water above it)', 'the surface particles hold together like a stretched skin (surface tension)', 'laid on gently, the thumbtack does not break the skin, so the skin holds it up'] points
So its neighbors pull it only sideways and down.
So the surface particles hold together like a tight, stretched skin.
The thumbtack is laid on gently, so it does not break the skin.
So the skin holds the thumbtack up.
Otto says: "The paper clip floats on the water because steel is less dense than water." Is Otto correct?
- A yes
- B no
Answer
Key: B — no
A denser object cannot float; dropped in, the clip sinks.
The resting clip is held up by the surface skin, so Otto is not correct.
Feedback per option
- A Steel at about 8 g/cm³ is denser than water at 1.0 g/cm³, so the clip is not floating. The surface skin holds it up.
- B Steel is denser than water, so the clip cannot float. The surface skin holds the resting clip up.
Gray circles are water particles. One particle in the top row is marked X. In which directions do X's neighbors pull it?
- A sideways and down
- B only down
- C up, down and sideways
Answer
Key: A — sideways and down
A particle's neighbors pull on it.
X's neighbors are beside it and below it, so they pull it only sideways and down.
Feedback per option
- A X is in the top row, so no water sits above it; its neighbors pull it only sideways and down.
- B X has neighbors beside it as well as below it, so X is pulled sideways too.
- C X has no neighbor above it, so no pull is upward; it is pulled sideways and down only.
A water particle sits deep inside a bowl of water, far below the surface. In which directions do its neighbors pull it?
- A only sideways
- B from every side
- C only down
Answer
Key: B — from every side
Every neighbor pulls on it.
So the particle is pulled from every side.
Feedback per option
- A Deep inside, the particle has neighbors above and below as well as beside it.
- B Deep inside the water, a particle has neighbors on every side, so it is pulled from every side.
- C Deep inside, the particle has neighbors above it and beside it too, not only below.
A mosquito lands on a pond and stands on the water without going under. What holds it up?
- A the mosquito is light enough to float like a cork
- B the water at the surface is thicker than the water below
- C the surface skin of the water holds its feet up
Answer
Key: C — the surface skin of the water holds its feet up
The mosquito's feet press the skin down a little but do not break it.
So the skin holds the mosquito up.
Feedback per option
- A Floating is for things less dense than water; the mosquito stands on the surface skin, denting it but not breaking it.
- B The surface water is the same water; the skin comes from the surface particles pulling on each other.
- C The mosquito's feet dent the surface skin but do not break it, so the skin holds the mosquito up.
A sewing needle rests on water. A fingertip pushes it down through the surface. What happens next?
- A it rises back to the surface
- B it floats just under the surface
- C it sinks to the bottom
Answer
Key: C — it sinks to the bottom
The fingertip pushes the needle through the skin.
Below the skin, steel is denser than water, so the needle sinks to the bottom.
Feedback per option
- A The skin held the needle up only while it was unbroken; steel denser than water does not rise.
- B Steel is denser than water, so below the skin the needle sinks all the way down.
- C The skin is broken, and steel is denser than water, so the needle sinks.
Is a steel clip resting on water floating the same way a cork floats?
- A yes
- B no
Answer
Key: B — no
Steel is denser than water, so a steel clip cannot float.
The resting clip is held up by the surface skin, so it is not floating the way a cork floats.
Feedback per option
- A A cork floats because it is less dense than water. Steel is denser than water, so the clip is held up by the surface skin, not floating.
- B Steel is denser than water, so the clip cannot float like a cork. The surface skin holds the clip up.
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 property explains it?
MAT-076 · Cohesion, adhesion, and surface tension explain everyday water phenomena — Match each of the three named phenomena (droplet formation, water rising in plants, insects walking on water) to the property that explains it.
Script
| Say | Screen |
|---|---|
| Here are three scenes from the same pond. | [the pond drawing] |
| A raindrop rounds itself into a bead on a lily pad. | [scene 1 highlighted] |
| Water climbs up inside the reeds' narrow stems. | [scene 2 highlighted; the water level inside the stem above the pond's] |
| A water strider, a thin insect with long legs, stands on the pond without sinking. | [scene 3 highlighted] |
| One of water's three properties, cohesion, adhesion or surface tension, explains each scene. | [the three scenes, each with an empty label slot under it] |
| Water pulling on water is cohesion; water pulling on another substance is adhesion. | [two chips: COHESION, ADHESION, each with its pull drawing] |
| The surface particles, pulled only sideways and down, hold together like a stretched skin, and that is surface tension. | [chip: SURFACE TENSION; the top row with its arrows] |
| The raindrop is water pulling on water, so it rounds into a bead, and that is cohesion. | [scene 1; label COHESION] |
| The water in the stem pulls on the stem's walls, and adhesion drags its edge up. | [scene 2; pull arrows to the stem walls] |
| Adhesion lifts the edge; cohesion pulls the rest up behind it. So the scene is adhesion. | [label ADHESION] |
| The strider's feet dip the skin without breaking it, and the skin holds it up, and that is surface tension. | [scene 3; the dents; label SURFACE TENSION] |
| So, to sort a scene, ask what is pulling on what. | [the rule slide: the three-scene table; nothing else printed] |
| Water rounding itself into a drop is cohesion; water clinging to another surface and climbing is adhesion; water's surface holding up a small object is surface tension. | [the three verdict chips light in turn: COHESION, ADHESION, SURFACE TENSION] |
| Okay, now your turn. | [closing screen: bullets — • Water on water, rounding into a drop: cohesion • Water clinging to another surface and climbing: adhesion • The surface holding up a small object: surface tension] |
“Okay, now your turn.” — the attached question
A raindrop beads on a lily pad, water climbs a reed's stem, and a water strider stands on a pond. Which scene is cohesion?
- A the raindrop beading on the lily pad
- B the water climbing the reed's stem
- C the water strider standing on the pond
Answer
Key: A — the raindrop beading on the lily pad
The raindrop is water pulling water into a rounded shape.
So the raindrop scene is cohesion.
Feedback per option
- A The raindrop is water pulling on water: cohesion.
- B The climbing water pulls on the stem's walls: adhesion.
- C The surface skin holds the strider up: surface tension.
Quiz after the video — the mastery check, 13 items
Which pull is water pulling on water?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: A — cohesion
Water on water is the same substance.
The pull between particles of the same substance is cohesion.
Feedback per option
- A The pull between particles of the same substance is cohesion.
- B Adhesion is water pulling on a different substance.
- C Surface tension is the skin effect at the surface, not the name of water pulling on water.
Which pull is water pulling on a different substance, such as paper?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: B — adhesion
Water on paper is two different substances.
The pull between particles of different substances is adhesion.
Feedback per option
- A Cohesion is water pulling on water.
- B The pull between particles of different substances is adhesion.
- C Surface tension is the skin effect at the surface, not water pulling on paper.
Which name is given to the skin effect at the surface of water?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: C — surface tension
The surface particles hold together like a stretched skin.
This skin effect is called surface tension.
Feedback per option
- A Cohesion is the pull between water particles; the skin effect it makes at the surface has its own name.
- B Adhesion is water pulling on a different substance.
- C The surface particles hold together like a stretched skin: surface tension.
A short piece of thin dry wire, laid flat on water, rests on top. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: C — surface tension
The water's surface skin holds the wire up.
Water's surface holding up a small object is surface tension.
Feedback per option
- A The wire is not pulled into a rounded shape; the surface holds it up.
- B The wire is not clinging to another surface and climbing; the water's surface holds it up.
- C The surface skin dips under the wire but does not break, so the skin holds it up: surface tension.
A drop of water sits as a round bead on a waxy apple. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: A — cohesion
The drop's water particles pull on each other and round the drop.
Water pulling water into a rounded shape is cohesion.
Feedback per option
- A Water pulls water into a rounded shape: cohesion.
- B The water is not clinging to the apple and climbing; it pulls itself into a bead.
- C No object rests on the water's surface; the water rounds itself.
Water climbs up the stalk of a celery stick standing in a cup of water. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: B — adhesion
The water pulls on the walls inside the stalk and climbs.
Water clinging to another substance and climbing is adhesion.
Feedback per option
- A Water is not being pulled into a rounded shape; it clings to the stalk and climbs.
- B The water clings to the walls inside the stalk and climbs: adhesion.
- C No object rests on the water's surface; the water climbs the stalk.
Water soaks up into a dry paper napkin laid on a spill. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: B — adhesion
The water pulls on the paper and climbs into it.
Water clinging to another substance and climbing is adhesion.
Feedback per option
- A The water is not rounding itself; it clings to the paper and climbs into it.
- B The water clings to the paper and climbs into the napkin: adhesion.
- C No object rests on the water's surface; the water climbs into the paper.
Two drops on a countertop run together into one drop. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: A — cohesion
The particles of one drop pull on the particles of the other: water on water.
Water pulling water together is cohesion.
Feedback per option
- A Water pulls on water, and the two drops gather into one: cohesion.
- B The joining is water on water, not water clinging to the countertop and climbing.
- C No object rests on the water's surface; the drops pull each other together.
A small beetle stands on a puddle without going under. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: C — surface tension
The puddle's surface skin holds the beetle up.
Water's surface holding up a small object is surface tension.
Feedback per option
- A The beetle is not water rounding itself; the puddle's surface holds it up.
- B The beetle is not water clinging to another substance; the puddle's surface holds it up.
- C The surface skin dips under the beetle's feet but does not break: surface tension.
Water climbs up a dry cotton string hung into a cup of water. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: B — adhesion
The water pulls on the cotton and climbs the string.
Water clinging to another substance and climbing is adhesion.
Feedback per option
- A The water is not rounding itself; it clings to the string and climbs.
- B The water clings to the cotton and climbs the string: adhesion.
- C No object rests on the water's surface; the water climbs the string.
Drips from a wet umbrella fall as round drops. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: A — cohesion
Each drop's water particles pull on each other and round the drop.
Water pulling water into a rounded shape is cohesion.
Feedback per option
- A Water pulls water into a rounded shape: cohesion.
- B The drops are not clinging to another substance and climbing; they round themselves.
- C No object rests on the water's surface; each drop rounds itself.
The table gives three scenes and what pulls on what in each. Which scene is adhesion?
- A a bead of water standing on a leaf
- B water soaking up into a dry stick of chalk
- C a dry steel staple resting on a puddle
Answer
Key: B — water soaking up into a dry stick of chalk
Water on chalk is two different substances pulling on each other.
Water clinging to another substance and climbing is adhesion, so the chalk is the adhesion scene.
Feedback per option
- A Water on water is the same substance: cohesion.
- B Water on chalk is two different substances, and the water climbs into the chalk: adhesion.
- C Water on water at the surface is the skin holding the staple up: surface tension, not adhesion.
Wren says: "The thin film of water left on a rinsed plastic lunchbox lid is adhesion, because the water pulls on the plastic." Is Wren correct?
- A yes
- B no
Answer
Key: A — yes
The water pulls on the plastic of the lid: two different substances.
That pull, adhesion, keeps the film clinging to the lid, so Wren is correct.
Feedback per option
- A The water pulls on the plastic, two different substances, and that pull keeps the film on the lid: adhesion.
- B Water on plastic is two different substances pulling on each other. That pull is adhesion, and it keeps the film on the lid.
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: Water's special properties
Script, part 1 (87 words)
| Say | Screen |
|---|---|
| Here is everything we found out about water's special properties. | [a still: the dome on the penny and the towel in the glass] |
| Water particles pull on each other. | [two gray circles; the double-headed arrow] |
| The pull between particles of the same substance is called cohesion. | [chip: COHESION] |
| Cohesion pulls the outer particles of a drop in toward the rest, so the water gathers into a rounded shape. | [the dome zoom as a still; outer arrows inward] |
| Water particles also pull on the particles of other substances, such as glass and paper. | [a gray circle beside a hatched band; the pull arrow] |
| The pull between particles of different substances is called adhesion. | [chip: ADHESION] |
| And to sort a case, ask what is pulling on what. | [the five cases under the chip SAME SUBSTANCE?] |
| Okay, now your turn. | [closing screen: bullets — • Water particles pull on each other: cohesion • Cohesion pulls a drop's outer particles in, so water rounds • Water also pulls on other substances: adhesion • Ask what is pulling on what] |
“Okay, now your turn.” — the check question between the parts
Water climbs up a paper towel dipped into a glass of water. Which pull is that?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: B — adhesion
Water pulls on paper, a different substance.
So the climb is adhesion.
Feedback per option
- A Cohesion is water pulling on water; the towel is a different substance.
- B Water pulling on paper is two different substances pulling: adhesion.
- C Surface tension is the skin at the surface holding something up; the towel climb is water pulling on paper.
Script, part 2 (94 words)
| Say | Screen |
|---|---|
| Here is everything we found out about the surface of water. | [a still: the skin zoom] |
| A particle at the surface has no water above it, so its neighbors pull it only sideways and down. | [particle S in the top row; four arrows] |
| The surface particles hold together like a tight, stretched skin. | [arrows along the top row] |
| This skin effect is called surface tension. | [chip: SURFACE TENSION] |
| A small object lowered gently does not break the skin, so it rests on top. | [the clip resting on the dipped top row] |
| And water rounding itself into a drop is cohesion; water clinging to another surface and climbing is adhesion; water's surface holding up a small object is surface tension. | [the three-scene table with its three chips] |
| Okay, now your turn. | [closing screen: bullets — • Surface particles are pulled only sideways and down • They hold together like a stretched skin: surface tension • A small object lowered gently rests on the skin] |
“Okay, now your turn.” — the two questions after part 2
A water strider stands on a pond without sinking. Which property explains it?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: C — surface tension
The pond's surface skin holds the strider up.
Water's surface holding up a small object is surface tension.
Feedback per option
- A Cohesion explains a raindrop beading: water pulling on water.
- B Adhesion explains water climbing a stem: water pulling on the stem's walls.
- C The surface skin holds the strider up: surface tension.
Two drops of water touch and join into one bigger drop. Which pull is that?
- A cohesion
- B adhesion
- C surface tension
Answer
Key: A — cohesion
Water pulls on water, the same substance.
So two drops joining is cohesion.
Feedback per option
- A Water pulling on water is cohesion.
- B Adhesion is water pulling on a different substance; here water pulls on water.
- C Surface tension is the surface skin holding something up; here water pulls on water.
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)
- Water particles pull on each other.
- The pull between particles of the same substance is called cohesion.
- Cohesion pulls the outer particles of a drop in toward the rest, so the water gathers into a rounded shape.
- Water particles also pull on the particles of other substances, such as glass and paper.
- The pull between particles of different substances is called adhesion.
- To sort a case, ask what is pulling on what.
- A particle at the surface has no water above it, so its neighbors pull it only sideways and down.
- The surface particles hold together like a tight, stretched skin.
- This skin effect is called surface tension.
- A small object lowered gently does not break the skin, so it rests on top.
- Water rounding itself into a drop is cohesion; water clinging to another surface and climbing is adhesion; water's surface holding up a small object is surface tension.
Scripts, questions and quizzes are read from the course content as it stands today; the student site for this topic is here.