Question 1

Which statement best describes the Law of Conservation of Mass?

Accepted Answer

The total mass of substances present before a chemical change equals the total mass of substances present after the change.

Question 2

A student burns 10.0 g of magnesium in air and collects 16.6 g of magnesium oxide. According to the Law of Conservation of Mass, how much oxygen was used in the reaction?

Accepted Answer

$$6.6\ \mathrm{g}$$

Question 3

Which of the following is a hypothesis?

Accepted Answer

A tentative explanation that can be tested by experiments.

Question 4

Which of the following is NOT a step in the scientific method as described in your notes?

Accepted Answer

Ignoring contradictory evidence

Question 5

A chemical reaction occurs in a closed container. The mass of the container and contents before the reaction is $$150\ \mathrm{g}$$, and after the reaction is $$150\ \mathrm{g}. $$What does this observation support?

Accepted Answer

The Law of Conservation of Mass

Question 6

Which of the following best defines a theory in science?

Accepted Answer

A well-tested explanation that unifies a broad range of observations

Question 7

Which scenario is an example of a chemical change?

Accepted Answer

Iron rusting when exposed to air

Question 8

A student proposes that plants grow faster when exposed to blue light. What part of the scientific method does this represent?

Accepted Answer

Formulating a hypothesis

Question 9

Which of the following is a correct application of the Law of Conservation of Mass in a real-world scenario?

Accepted Answer

When burning wood in a closed system, the total mass of the system remains unchanged.

Question 10

Which statement about scientific laws is correct?

Accepted Answer

Scientific laws summarize observed patterns in nature.

Question 11

If a chemical reaction in an open container results in a decrease in mass, what is the most likely explanation?

Accepted Answer

Some product escaped as a gas.

Question 12

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

Accepted Answer

Evaporating water from a puddle

Question 13

A scientist observes that a solution changes color when mixed with another chemical. What is the next step in the scientific method?

Accepted Answer

Formulate a hypothesis to explain the color change.

Question 14

Which of the following best describes an experiment?

Accepted Answer

A procedure carried out to test a hypothesis.

Question 15

Which of the following is NOT a characteristic of a good hypothesis?

Accepted Answer

It is proven true before experimentation.

Question 16

A student mixes two clear solutions and observes a white precipitate forms. What type of change has occurred?

Accepted Answer

Chemical change

Question 17

Which of the following is the best example of a scientific law?

Accepted Answer

The Law of Conservation of Mass: $$	ext{mass}_{	ext{reactants}} = 	ext{mass}_{	ext{products}}$$

Question 18

Which of the following is a correct statement about the difference between a law and a theory?

Accepted Answer

A theory explains why phenomena occur, while a law describes what happens.

Question 19

A student observes that the mass of a sealed flask does not change after a chemical reaction. Which principle does this observation illustrate?

Accepted Answer

Law of Conservation of Mass

Question 20

Which of the following is the correct sequence of steps in the scientific method?

Accepted Answer

Observation, hypothesis, experiment, conclusion

Introduction to Chemistry: Scientific Method, Laws, and Experimental Design

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