Solids, Liquids, and Gases (Lesson 2, Changes of State)

Question 1

When thinking about solids, liquids, and gases, which has more thermal energy, and which has the least?

Answer 1

Gas is the highest, liquid is next, and solids have the least.

Question 2

In order to change from a solid to a liquid, and a liquid to a gas, what has to increase?

Answer 2

Thermal energy

Question 3

In order to change from a liquid to a solid, or a gas to a liquid, what has to decrease?

Answer 3

Thermal energy

Question 4

What is melting?

Answer 4

The change in state from a solid to a liquid.

Question 5

What is the melting point?

Answer 5

In pure, crystalline solids, melting occurs at a specific temperature.

Question 6

How do scientists use melting points to identify unknown material?

Answer 6

The compare the melting point of known substances to the melting point of the unknown substance.

Question 7

What is the melting point of water?

Answer 7

O degrees C, 32 degrees F

Question 8

What happens at a solid’s melting point?

Answer 8

Its particles vibrate so fast that they break free from their fixed positions.

Question 9

What is freezing?

Answer 9

The change of state from a liquid to a solid.

Question 10

What happens at a liquid’s freezing point?

Answer 10

Its particles are moving so slowly that they begin to take on fixed positions with each other.

Question 11

What is the freezing point of water?

Answer 11

0 degrees C, 32 degrees F

Question 12

What is vaporization?

Answer 12

The change of state from a liquid to a gas

Question 13

What are the two main types of vaporization?

Answer 13

Evaporation and boiling

Question 14

What is evaporation?

Answer 14

Vaporization that takes place only on the surface of a liquid after gaining energy.

Question 15

How does evaporation of a puddle work?

Answer 15

It gains energy from the ground, air, or the sun. The added energy allows some of the water molecules on the surface to escape into the air.

Question 16

What is boiling?

Answer 16

Vaporization that takes place both below and at the surface of a liquid after gaining energy.

Question 17

How does the boiling of water work?

Answer 17

Added energy allows the water molecules to vaporize. The vaporized water below the surface forms bubbles and then rises to the surface.

Question 18

What is the boiling point?

Answer 18

The temperature at which a liquid boils (vaporizes).

Question 19

How do chemists use boiling points to help identify unknown substances?

Answer 19

They compare the boiling point of the unknown liquid to the boiling points of known liquids.

Question 20

What is condensation?

Answer 20

The change of state from a gas to a liquid.

Question 21

When does condensation occur?

Answer 21

When particles in a gas lose enough thermal energy to form a liquid.

Question 22

How do clouds form?

Answer 22

When water vapor (gas) in the atmosphere condenses into tiny liquid droplets. When the droplets get heavy enough, they fall to the ground as rain.

Question 23

Can you see water vapor?

Answer 23

No, water vapor is a colorless gas that you cannot see?

Question 24

Is the steam you see above a boiling kettle, in the shower, or fog outside water vapor?

Answer 24

No, what you see is tiny droplets of liquid water suspended in the air.

Question 25

What is sublimation

Answer 25

When the surface particles of a solid gain enough energy that they from a gas. They do not pass through the liquid state before becoming a gas.

Question 26

What causes snow to disappear even when the temperature outside is well below freezing?

Answer 26

The energy from the sun causes sublimation ( turning from a solid to a gas without ever being a liquid).

Question 27

How does sublimation occur with dry ice?

Answer 27

Dry ice, which is frozen carbon dioxide, turns from a solid to a gas when thermal energy from the atmosphere is added. Carbon dioxide cannot exist as a liquid at ordinary atmospheric pressures.

Question 28

Why is dry ice used to keep something cool when a refrigerator isn’t available?

Answer 28

It won’t ruin the material because it turns from a solid directly to a gas (sublimation).

Question 29

Why is dry ice used in some fog machines?

Answer 29

When the solid dry ice turns directly into a gas (sublimation) as it absorbs surrounding thermal energy, it cools the water vapor in the nearby atmosphere, turning it into small water droplets.