Question 1

Which of the following best describes the state of matter for formaldehyde at room temperature (25 °C), given its melting point is –92 °C and boiling point is –19.5 °C?

Accepted Answer

Liquid, because room temperature is between its melting and boiling points.

Question 2

Which of the following statements about the states of matter is correct?

Accepted Answer

A solid has a definite volume and shape.

Question 3

During the melting of ice, which of the following is true regarding enthalpy ($$\Delta H) $$and entropy ($$\Delta S$$)?

Accepted Answer

$$\Delta H is $$positive and $$\Delta S is $$positive.

Question 4

Which process is exothermic and results in a decrease in disorder?

Accepted Answer

Freezing of water

Question 5

A sample of vanilla ice cream is best classified as which of the following?

Accepted Answer

A homogeneous mixture

Question 6

Which of the following best describes sugar (sucrose)?

Accepted Answer

A compound

Question 7

Which of the following equations correctly represents the enthalpy change for the melting of ice?

Accepted Answer

$$\mathrm{H_2O(s) \rightarrow H_2O(l)}$$  $$\Delta H = +6.02\ \mathrm{kJ/mol}$$

Question 8

Which of the following best explains why gases have neither a definite shape nor a definite volume?

Accepted Answer

The kinetic energy of the particles is much greater than the attractive forces between them.

Question 9

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

Accepted Answer

Melting ice to form liquid water

Question 10

Which of the following statements about mixtures and pure substances is correct?

Accepted Answer

A pure substance can be either an element or a compound.

Question 11

Which of the following best describes the entropy change ($$\Delta S) $$when water freezes?

Accepted Answer

$$\Delta S is $$negative because disorder decreases.

Question 12

Which of the following is a correct classification for air?

Accepted Answer

A homogeneous mixture

Question 13

Which of the following best describes the energy changes during the freezing of water?

Accepted Answer

Heat is released and $$\Delta H is $$negative.

Question 14

Which of the following is NOT a characteristic of a solid?

Accepted Answer

Particles are free to move past each other

Question 15

Which of the following best explains why melting is an endothermic process?

Accepted Answer

Energy is absorbed to overcome attractive forces between particles.

Question 16

Which of the following is a heterogeneous mixture?

Accepted Answer

Vanilla ice cream with visible vanilla bean specks

Question 17

Which of the following best describes the classification of copper wire?

Accepted Answer

An element

Question 18

Which of the following is true about the boiling of water?

Accepted Answer

It is an endothermic process with an increase in entropy.

Question 19

Which of the following best describes the relationship between kinetic energy and the state of matter?

Accepted Answer

Gases have the highest kinetic energy among the three states.

Question 20

Which of the following is a correct statement about compounds?

Accepted Answer

Compounds have a fixed composition and can be broken down into simpler substances by chemical means.

Matter and Its States: Classification and Changes

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