7.2 Check and Reflect

Key Concept Review

1.       Explain why a solid substance occupies less space than the same substance in gaseous form.

The particles in a solid are closer together since they have stronger forces of attraction. The weaker forces of attraction in gases allow them to move further apart.

2.       Explain why the particles of a liquid are able to pour into a container and then take on the shape of that container.

The forces of attraction in liquids are weaker than solids so the particles can move past each other. However, they are not free enough like gases to fill any space they are in.

3.       Explain what happens to the particles of a substance that changes state from liquid to gas.

The energy added to the particles causes them to speed up so fast, that the forces of attraction between them cannot hold them together. They break apart and form a gas.

4.       Explain why ice cubes placed in your refrigerator’s freezer section become smaller over time.

The air circulating in the freezer causes the ice cubes to sublimate. The air picks up frozen water and turns it directly into water vapour.

Connect Your Understanding

5.       Use the particle theory of matter to explain how the particles in an ice cube differ from the particles in a glass of water.

Ice: particles are vibrating, stronger forces of attraction, less space between particles, cannot move freely, keeps its shape

Water: particles are moving faster, weaker forces of attraction, more space between particles, particles can move past each other, takes the shape of its container

6.       Use the particle theory of matter to explain what happens to the particles in a hot drink when it cools down.

The particles in the hot drink lose energy to the surrounding air and the cup or mug it is in. The fast moving drink particles speed up the slower moving air particles and cup particles. This slows the drink particles down.

7.       Use the particle theory of matter to explain why heat is required to boil water.

Energy is needed to speed up the particles and overcome the forces of attraction.