Question 1

Which of the following best describes a compound?

Accepted Answer

A substance made of two or more elements chemically combined in fixed proportions.

Question 2

Which of the following is an example of a physical change?

Accepted Answer

Melting of ice into water.

Question 3

A student mixes silver and iron filings together. Which statement best describes the result?

Accepted Answer

A mixture is formed, and the components can be separated by physical means.

Question 4

Which of the following is NOT a characteristic of a pure substance?

Accepted Answer

It can be separated into simpler substances by physical means.

Question 5

Which process is an example of a chemical change?

Accepted Answer

Combustion of methane: $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$

Question 6

Which statement about the movement of particles in different states of matter is correct?

Accepted Answer

Particles in a gas move freely and rapidly compared to those in a solid.

Question 7

A sample of mercury is cooled from $$25^\circ\mathrm{C} to$$ $$-40^\circ\mathrm{C}. $$What phase change occurs?

Accepted Answer

Liquid to solid (freezing)

Question 8

Which of the following best explains why a compound has different properties than the elements that compose it?

Accepted Answer

Chemical bonds form between atoms, resulting in new substances with unique properties.

Question 9

Which of the following is a homogeneous mixture?

Accepted Answer

Saltwater solution

Question 10

Which statement about scientific methods in chemistry is most accurate?

Accepted Answer

Scientific methods involve making observations, forming hypotheses, and conducting experiments to test ideas.

Question 11

A student observes that a liquid turns into a gas when heated. Which term best describes this process?

Accepted Answer

Vaporization

Question 12

Which of the following is an example of an exothermic chemical change?

Accepted Answer

Combustion of propane: $$\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}$$

Question 13

Which of the following best describes the difference between a mixture and a compound?

Accepted Answer

Mixtures can be separated by physical means, while compounds require chemical means for separation.

Question 14

Which of the following is a chemical property?

Accepted Answer

Ability of iron to rust when exposed to oxygen.

Question 15

A scientist observes that a substance changes from solid directly to gas. What is this process called?

Accepted Answer

Sublimation

Question 16

Which of the following is an example of a heterogeneous mixture?

Accepted Answer

A salad with lettuce, tomatoes, and cucumbers.

Question 17

Which statement best explains why scientific theories are important in chemistry?

Accepted Answer

They provide explanations for observed phenomena and predict future outcomes.

Question 18

Which of the following is a correct representation of a chemical reaction?

Accepted Answer

$$\mathrm{2H_2 + O_2$ \rightarrow 2H_2O}$$

Question 19

A mixture of sand and salt is added to water and stirred. Which method would best separate the sand from the saltwater solution?

Accepted Answer

Filtration

Foundations of Chemistry: Structure, Composition, and Changes of Matter

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