MS Chemistry · Form E — the end-of-course test (40 items, drawn across Checkpoints 1–3 by reference)

Which box shows the particles of a gas?

1. box A
2. box B
3. box C
4. box D

A scientist counts the protons in every atom of a sample. Every atom has 29 protons. Which category is the sample?

1. a compound
2. a mixture
3. a molecule
4. an element

Each size and shade of circle is a different kind of atom. Touching circles are joined. Which of these could this drawing show?

1. titanium, Ti
2. titanium dioxide, TiO₂
3. a mixture of titanium and oxygen
4. a mixture of titanium dioxide and oxygen

Aluminum's atomic number is 13. How many electrons does a neutral aluminum atom have?

1. 0 electrons
2. 13 electrons
3. 14 electrons
4. 26 electrons

In this part of the periodic table, each box shows the element's atomic number at the top, its symbol in the middle, and its name below. A label reads Na₂Se. Find the element the symbol Se stands for. Which element is it?

1. sulfur
2. silicon
3. strontium
4. selenium

Four elements are tested on a bench. Which one is a metalloid?

1. a dull gas that leaves the bulb dark
2. a shiny solid that bends without breaking when it is struck and lights the bulb brightly
3. a shiny solid that shatters when it is struck and makes a bulb glow only faintly
4. a dull solid that crumbles and leaves the bulb dark

The mineral fluorite is calcium fluoride, CaF₂; Ca is calcium, F is fluorine. How many atoms does one CaF₂ particle hold, and how many kinds of atom?

1. 2 atoms of 2 kinds
2. 3 atoms of 3 kinds
3. 2 atoms of 3 kinds
4. 3 atoms of 2 kinds

Two clear liquids are poured together: barium chloride + sodium sulfate → barium sulfate + sodium chloride. The barium sulfate settles out as white grains. Which sign of a chemical change does this scene show?

1. a gas forming
2. a temperature change
3. a solid forming
4. light given out

A base neutralizes an acid: calcium hydroxide + hydrochloric acid → calcium chloride + water. Which two substances are the reactants?

1. calcium chloride and water
2. hydrochloric acid and water
3. calcium hydroxide and hydrochloric acid
4. calcium hydroxide, water and calcium chloride

Zinc reacts with hydrochloric acid: Zn + 2HCl → ZnCl₂ + H₂. How many hydrogen atoms are on each side of the arrow?

1. 1 atom on each side
2. 2 atoms on each side
3. 2 atoms on the left and 1 atom on the right
4. 4 atoms on each side

Which of these scenes shows cohesion?

1. An iron gate left out in the rain grows orange, crumbly patches.
2. Rainwater climbs up into the bottom of a paper bag lying on the ground.
3. A puddle on a garden path shrinks and disappears in the afternoon sun.
4. Drops of water stand as round beads on a greased baking tray.

A neutralization is written as a word equation: potassium hydroxide + hydrochloric acid → potassium chloride + water. Which substance in it is the base?

1. potassium hydroxide
2. hydrochloric acid
3. potassium chloride
4. water

A base is stirred into an acid in a beaker on the bench. A thermometer standing in the liquid climbs from 20 °C to 24 °C, and nothing is heating the beaker. Which sign of a chemical change is this?

1. a gas forming
2. a solid forming
3. a temperature change
4. a color change

The two boxes show the particles in two samples of the same liquid. The arrows show how fast the particles move. Which sample is warmer?

1. sample A
2. sample B
3. Both are at the same temperature.
4. You cannot tell from the arrows.

Ngozi sweeps a workshop floor and holds a magnet over the sweepings. Gray flakes jump onto the magnet, and sawdust stays behind. What do the two heaps show about the sweepings?

1. The sweepings were a pure substance.
2. The magnet turned part of the sweepings into steel.
3. The sweepings were a mixture.
4. The sweepings became a mixture when the magnet touched them.

A sealed bottle holds water with a sugar cube resting in it. The bottle reads 420 g on a balance. Zia shakes the bottle until the whole cube has dissolved. What does the balance read now?

1. less than 420 g
2. 420 g
3. more than 420 g
4. You cannot tell without the mass of the cube.

A helium atom has 2 protons in its nucleus. One proton is taken out of a helium atom and kept on its own. Which statement about that proton is correct?

1. It is not helium: one whole atom is the smallest piece of helium.
2. It is not helium yet: it becomes helium again only when it joins a clump of other protons.
3. It is helium: it came out of a helium atom.
4. It is helium: a proton is what makes an atom helium.

Silver nitrate, AgNO₃, was used in old photography; Ag is silver, N is nitrogen, O is oxygen. Every oxygen atom has 8 protons. How many atoms in one AgNO₃ particle have 8 protons?

1. 1 atom
2. 3 atoms
3. 5 atoms
4. 8 atoms

The heavy zigzag line is the staircase. Sand is mostly silicon dioxide, SiO₂. Find the two elements of SiO₂ on this part of the table. Which of them is a metalloid?

1. silicon
2. oxygen
3. both of them
4. neither of them

In this part of the periodic table, each box shows the element's atomic number at the top and its symbol in the middle. The numbers across the top of this part of the table are the group numbers; the numbers down the side are the period numbers. One cell is ringed. How many protons does each atom of the ringed element have, and in which period does the element sit?

1. 23 protons, period 3
2. 23 protons, period 4
3. 5 protons, period 4
4. 5 protons, period 3

MnO is a green powder and MnO₂ is a black powder; Mn is manganese, O is oxygen. A student tips both powders into one jar and stirs them together. How many substances does the jar hold?

1. one substance: both powders are manganese oxide
2. two substances mingled: a mixture
3. one compound written two ways
4. three substances: manganese, oxygen and the powder

Each size and shade of circle is a different kind of atom, and touching circles are joined. The two boxes show the atoms before and after a change. Which kind of change is this, and why?

1. a physical change, because the same kinds of atom are in both boxes, in the same numbers
2. a physical change, because the particles only moved to new places in the box
3. a chemical change, because some of the atoms were used up in the change
4. a chemical change, because the atoms have new partners, so new particles formed

A student writes the line ice → liquid water for an ice cube melting. Why is this line not the word equation of a chemical reaction?

1. The substance on the right is the same substance as on the left, so no new substance formed.
2. A word equation needs a plus sign on the left of the arrow, and this line has no plus sign anywhere.
3. Water cannot be written in a word equation, because it is a liquid and not a gas.
4. Melting has no arrow, because a change that happens slowly is not written this way.

In a lidded flask, 7.3 g of hydrochloric acid reacts with exactly 5.8 g of magnesium hydroxide: hydrochloric acid + magnesium hydroxide → magnesium chloride + water. The reaction makes 3.6 g of water. What mass of magnesium chloride, the salt, does it make?

1. 3.7 g
2. 9.5 g
3. 13.1 g
4. 16.7 g

A student writes a neutralization in formulas: KOH + HNO₃ → KNO₃ + H₂. Which element's count does not match on the two sides?

1. hydrogen
2. nitrogen
3. oxygen
4. potassium

A sprig of water weed stands in a sunlit jar of water. Bubbles rise from its leaves, and a test shows the gas is oxygen. Which statement is correct?

1. The bubbles are oxygen that the plant made from carbon dioxide and water: a new substance formed, so a reaction happened.
2. The bubbles are air that was dissolved in the water and is now escaping as the jar warms up in the sun, so no chemical reaction happened at all.
3. The bubbles show that the water in the jar is boiling in the sun, and boiling is a physical change.
4. The oxygen in the bubbles came out of the soil at the plant's roots, where it had been stored.

The hatched band is a glass rod, and the light gray shape is water. Before: the tip of a dry glass rod touches the surface of the water in a dish. After: the rod is lifted, and a rounded drop hangs from its tip. Which pull holds the drop onto the glass?

1. cohesion, the water pulling on water
2. adhesion, the water pulling on the glass
3. surface tension, the skin lifting the water
4. no pull at all: the rod scooped the drop up

One water particle is one molecule: two hydrogen atoms joined to one oxygen atom. Which statement tells cohesion apart from the joins inside one water particle?

1. The joins hold the three atoms together as one particle; cohesion pulls one whole particle toward the next.
2. Cohesion is the name for the join between the two hydrogen atoms and the oxygen atom inside one water particle.
3. The joins inside a particle and cohesion between particles are two names for one and the same pull.
4. Cohesion pulls the three atoms of one particle apart so that each can join a different particle.

The scale marks a liquid's pH. Vinegar reads pH 3 on a meter. A student stirs a lot of water into the vinegar. Which reading could the meter give now?

1. pH 2
2. pH 3, exactly as before
3. pH 4
4. pH 8

An acid reads pH 2. A little base is stirred in, not enough to use up all the acid. Blue litmus paper is then dipped into the liquid. What does the paper do?

1. It stays blue, because the base that went in has made the liquid neutral.
2. It turns blue, then red, as the two react on the paper.
3. It turns white, because the base bleaches the dye out of it.
4. It turns red, because acid is left and the liquid is still acidic.

Two cups of the same kind hold 100 mL of cooking oil and 100 mL of water. Each balance was zeroed with its empty cup. The oil is poured gently into the water. What happens?

1. The oil floats on top of the water.
2. The water floats on top of the oil.
3. The oil and the water mix into one layer.
4. You cannot tell without the two densities.

Yuki opens a cup of yogurt that has fruit pieces at the bottom and plain yogurt on top. She sorts it as a pure substance because "it is all one food." Which statement about Yuki's sort is correct?

1. Yuki is wrong: fruit and yogurt are two kinds of matter, unevenly spread.
2. Yuki is correct: anything sold as one food is one kind of matter.
3. Yuki is wrong: the cup is homogeneous, because everything in it is a kind of yogurt.
4. Yuki is correct: only clear liquids can be mixtures.

Aluminum, Al, is a shiny metal that conducts electricity well. Oxygen, O₂, is a gas. Aluminum oxide, Al₂O₃, is the hard white grit on some sandpaper, and it does not conduct electricity. Bea says: "Al₂O₃ can hold aluminum atoms and still not conduct, because an Al₂O₃ particle is a new particle with its own properties." Which statement about Bea's claim is correct?

1. Bea is wrong: anything that holds metal atoms conducts electricity.
2. Bea is wrong: Al₂O₃ stops conducting only because its aluminum atoms have been used up.
3. Bea is wrong: Al₂O₃ is a mixture of aluminum and oxygen, and the oxygen gas between the aluminum atoms blocks the current.
4. Bea is correct: a compound's particles are new particles, so a compound has its own properties.

HF and HCl are both acids. Dmitri says: "HBr should be an acid too, because bromine sits right next to chlorine in the same row." Which statement about Dmitri's claim is correct?

1. Dmitri is correct: neighbors in a row behave alike.
2. HBr should be an acid, but because bromine sits below chlorine in the same group, not beside it in a row.
3. HBr should not be an acid: bromine is in a different row from chlorine.
4. The periodic table says nothing about compounds, so no prediction about HBr can be made from where bromine sits on it.

A label reads PbS. Bianca says: "One PbS particle holds 3 atoms: P, b and S." Rafi says: "One PbS particle holds 2 atoms." Who is correct?

1. Bianca
2. both of them
3. Rafi
4. neither of them

A zinc strip stands in a blue liquid in a lidded jar. Overnight the strip is coated red-brown and the liquid turns colorless; a balance reads 184.0 g before and after. Zofia says: "Same reading, so no new substance formed." Which statement is correct?

1. Zofia is correct: a chemical change always changes the reading, so a steady reading means a physical change.
2. The reading stays the same in every change in a lidded jar; the red-brown coat, which neither the zinc nor the liquid was, shows a new substance formed.
3. Zofia is correct: the red-brown coat was in the blue liquid all along and settled onto the strip, because nothing was added to the jar.
4. The reading should have risen when the coat grew on the strip, so the balance must be broken, and the jar should be weighed again on a different balance.

Two drops of water on a window slide until they touch and run together into one drop. Tarek says: "The drops joined into one, so their particles joined: a chemical reaction." Which statement is correct?

1. Tarek is correct: whenever two separate things become one single thing, a chemical reaction has happened between them, whatever they are made of.
2. The water particles pull on each other and gather into one drop, but no atom changed partners, so this is not a reaction.
3. Tarek is correct: the water particles joined into bigger particles, which is what a reaction does.
4. It is a reaction, because the glass of the window joined with the water as the drops ran together.

12 g of an acid reacts with exactly 8 g of a base in a lidded flask. Kwesi says: "The flask holds 20 g of salt and water now, but that total cannot tell me how much is salt." Which statement is correct?

1. Kwesi is correct: the law fixes the products' total mass, not how the 20 g is shared between the salt and the water.
2. Kwesi is not correct: the salt's atoms all came from the acid, so the salt's mass is 12 g and the water's is 8 g.
3. Kwesi is not correct: two products formed, so each has half of the total, 10 g of salt and 10 g of water.
4. Kwesi is not correct: the total is less than 20 g, because water is lighter than an acid and some mass is lost making it.

A dry steel pin lowered gently onto still water rests on top. The same pin is dipped in water so it is wet all over, then lowered just as gently: it sinks. The film of water on the pin weighs almost nothing. Why does the wet pin sink?

1. The wet pin is heavier than the dry pin was, so it breaks the skin, and steel that is under the skin sinks.
2. The wet pin is denser than the dry pin, and a denser object always goes under.
3. The film of water on the pin melts the skin where the pin touches the surface.
4. Water pulls on the wet steel, so it climbs onto the pin and closes over it instead of holding it up.

A base is added to an acid, and the meter reads 7. The liquid stayed clear and colorless the whole time. Matias says: "No reaction happened: a reaction always changes the color of the liquid." Which statement is correct?

1. Matias is correct: without a color change there is no chemical change, whatever a meter says.
2. Matias is correct: a neutralization is only two liquids mixing, not a chemical reaction.
3. Matias is not correct, because the liquid did in fact change color as the base went in: it changed from colorless to perfectly clear.
4. Matias is not correct: new substances, a salt and water, formed, and a color change is only one clue that a reaction may show.