Matter & Mixtures
A sample contains iron filings and sulfur powder. Both substances can still be seen, and a magnet can remove the iron.
How should the sample be classified?
A. Element
B. Compound
C. Mixture
D. Molecule
C. Mixture
The substances keep their original properties and are not chemically bonded.
What generally happens to particles when temperature increases?
A. They become larger.
B. They move faster.
C. More particles are created.
D. Their mass increases.
B. They move faster.
During a chemical reaction, atoms are—
A. created.
B. destroyed.
C. rearranged.
D. changed into energy.
C. rearranged.
Which observation provides the strongest evidence that a new substance formed?
A. A substance was stirred.
B. Two solids were mixed together.
C. A new solid with different properties appeared.
D. The substances remained the same color.
C. A new solid with different properties appeared.
Where does stored energy from food become available for the body to use?
A. In the mouth
B. In the stomach
C. In cells during chemical reactions
D. In the lungs
C. In cells during chemical reactions
Which statement best describes a compound?
A. Two substances placed in the same container
B. Two or more different kinds of atoms chemically joined in a fixed ratio
C. A substance made of only one type of atom
D. Any material that can be separated physically
B. Two or more different kinds of atoms chemically joined in a fixed ratio
A sealed syringe contains air. The temperature increases, and the plunger is free to move. The volume of the gas increases.
Which explanation is best?
A. New particles entered the syringe.
B. The particles became larger.
C. The particles moved faster and spread farther apart.
D. The particles changed into another substance.
C. The particles moved faster and spread farther apart.
A sealed flask contains 4.0 g of metal and 10.0 g of solution. A reaction produces a gas.
What is the mass of the contents after the reaction?
A. 10.0 g
B. 12.0 g
C. 14.0 g
D. Less than 14.0 g because gases have no mass
C. 14.0 g
Iron filings and sulfur are heated. Before heating, the iron can be removed with a magnet. After heating, the new black material cannot be attracted by a magnet.
Why is this evidence of a chemical reaction?
A. The iron became smaller.
B. One identifying property of the original iron changed.
C. Heating always causes chemical reactions.
D. The total mass remained the same.
Answer: B
Physical properties before and after a change to determine whether the substances' identities changed.
What happens to food molecules inside an organism?
A. They remain unchanged forever.
B. Their atoms are rearranged into new molecules.
C. Their atoms disappear when energy is needed.
D. Cells create new atoms from food energy.
Answer: B
digestion and cellular reactions as processes in which food molecules are broken down and their atoms are rearranged while energy is released
Which TWO substances are compounds?
A. Oxygen gas, O₂
B. Copper, Cu
C. Carbon dioxide, CO₂
D. Water, H₂O
E. Air
Answer: C and D
Explanation: Compounds contain atoms of different elements chemically joined.
A gas is compressed from 30 mL to 15 mL while its temperature remains constant.
Which statement is correct?
A. The particles move twice as fast.
B. The particles are closer together but move at approximately the same speed.
C. Half the particles disappear.
D. The particles become smaller.
B. The particles are closer together but move at approximately the same speed.
A reaction begins with:
2 carbon atoms
6 hydrogen atoms
7 oxygen atoms
The product model shows:
2 carbon atoms
6 hydrogen atoms
5 oxygen atoms
What's wrong?
A. Nothing
B. Two oxygen atoms are unaccounted for.
C. There are too many carbon atoms.
D. Products should always contain fewer atoms.
B. Two oxygen atoms are unaccounted for.
Two clear liquids are combined. A cloudy mixture forms and a white solid settles to the bottom.
Which conclusion is best supported?
A. No reaction occurred because both materials began as liquids.
B. A chemical reaction likely occurred because a new solid formed.
C. No reaction occurred because the temperature stayed constant.
D. The liquids only experienced a change of state.
B. A chemical reaction likely occurred because a new solid formed.
Why does a person breathe out more carbon dioxide during strenuous exercise?
A. Exercise creates carbon atoms.
B. More chemical reactions occur in cells to release energy from food molecules.
C. Carbon dioxide is stored unchanged inside food.
D. The lungs create carbon dioxide.
B. More chemical reactions occur in cells to release energy from food molecules.
A student separates salt and sand by dissolving the salt in water, filtering out the sand, and evaporating the water. Both substances have the same properties afterward.
What does this show?
A. A chemical reaction occurred.
B. The substances became compounds.
C. No chemical reaction occurred because the substances kept their identities.
D. New atoms were created.
C. No chemical reaction occurred because the substances kept their identities.
A sealed, rigid metal container of gas is heated. Which TWO changes occur?
A. The particles move faster.
B. The particles become larger.
C. The number of particles increases.
D. Particles collide with the walls more often.
E. The particles spread much farther apart.
A. The particles move faster.
D. Particles collide with the walls more often.
A student mixes 12.0 g of baking soda with 50.0 g of vinegar in an open flask. After bubbling stops, the measured mass is 60.5 g.
Why did the measured mass decrease?
A. Atoms were destroyed.
B. Gas formed and escaped the open system.
C. Baking soda has less mass after reacting.
D. Energy destroyed some of the matter.
Answer: B
If the same reaction occurs in a sealed container, the total remains 62.0 g because all of the atoms remain inside the system.
A student wants to determine whether mixing two powders causes a chemical reaction.
Which plan provides the best evidence?
A. Measure only the mass before and after mixing.
B. Compare characteristic properties before and after mixing.
C. Observe whether both are solids.
D. Stir the powders for a longer time.
Answer: B
Explanation: Students need evidence that the identity of the substances changed, not simply evidence that the materials were combined.
Two hikers eat the same breakfast. Later, Hiker 1 rests while Hiker 2 climbs a steep hill. Hiker 2 breathes out more carbon dioxide.
What is the best explanation?
A. Hiker 2 ate more food.
B. Hiker 2's cells used more food molecules in energy-releasing chemical reactions.
C. Hiker 1 stopped using energy completely.
D. Carbon dioxide provides energy for Hiker 2.
Answer: B
increased activity with greater food-molecule processing and carbon-dioxide production
An unknown white solid is suspected to be a mixture of two compounds. Which TWO observations would best support that claim?
A. Every sample has the same melting point.
B. Some of the solid dissolves in water while some remains.
C. Two differently shaped types of crystals are visible.
D. The solid has the same mass before and after testing.
E. The entire sample dissolves uniformly.
B. Some of the solid dissolves in water while some remains.
C. Two differently shaped types of crystals are visible.
A sealed flexible bottle of air is moved from a warm room into cold weather. The bottle begins collapsing inward.
Which TWO statements best explain why?
A. The particles lose energy and move more slowly.
B. Air particles escape through the bottle.
C. The particles collide with the walls less frequently and with less force.
D. The number of particles decreases.
E. The particles change into a liquid.
A. The particles lose energy and move more slowly.
C. The particles collide with the walls less frequently and with less force.
A closed system begins with 25.0 g of substance X and 15.0 g of substance Y. Two products form. One product has a mass of 18.0 g.
What is the mass of the second product?
A. 7.0 g
B. 18.0 g
C. 22.0 g
D. 40.0 g
C. 22.0 g
Explanation:
25 + 15 = 40 g total reactants
40 − 18 = 22 g
The total mass of the products must equal the total mass of the reactants in the closed system.
A cold pack becomes much colder after two substances inside it are mixed. Which conclusion is most scientifically accurate?
A. No reaction occurred because heat was not released.
B. Energy was destroyed.
C. The interaction absorbed energy from the surroundings and stored it.
D. The cold pack created cold energy.
C. The interaction absorbed energy from the surroundings and stored it.
A young animal eats plants and doubles in size over several months. Which TWO statements explain how its food supports growth?
A. Atoms from food are rearranged into new molecules that build body tissue.
B. Food remains unchanged and simply fills the animal's body.
C. Cells create new atoms using energy.
D. Energy becomes atoms.
E. Chemical reactions release energy from food that can support growth.
that food provides both matter for building new molecules and stored chemical energy for life processes