Physical and Chemical Changes - 7.2 Understanding Physical Change [ARCHIVE]

Question 1

What is the particle model?

Answer 1

A simplified representation of solids, liquids and gases explaining of their properties

Question 2

What are the assumptions of the particle model?

Answer 2

Particles are…
- Hard/incompressible
- Indivisible
- Attracted to each other
- Constantly moving.

Question 3

Why are solids incompressible and hold their shape?

Answer 3

Because the particles are tightly bound together by strong attraction and vibrate in fixed positions.

Question 4

How do particles in liquids behave compared to solids?

Answer 4

Liquid particles are packed closely but move freely, allowing liquids to flow and take the shape of their container.

Question 5

Why are gases compressible? (Pressure)

Answer 5

Gas particles have large spaces between them and move freely in straight lines until they collide.

Question 6

How does the particle model explain expansion in solids?

Answer 6

As temperature increases, particles vibrate more, pushing them further apart, causing expansion.

Question 7

What happens to solids when they contract?

Answer 7

When cooled, particles vibrate less and pack more tightly, causing contraction.

Question 8

How does temperature affect the particles in a liquid?

Answer 8

Higher temperatures increase particle vibrations and movement, causing liquids to expand.

Question 9

Why do gases expand when heated?

Answer 9

Gas particles move faster and hit the container more frequently, causing the container to expand if flexible.

Question 10

What is melting in terms of the particle model?

Answer 10

When a solid is heated, particle vibrations increase until they break free from their fixed positions, becoming a liquid.

Question 11

How does freezing occur?

Answer 11

As a liquid cools, particles lose energy and the attraction between them fixes them into solid positions.

Question 12

What is a mixture?

Answer 12

A combination of two or more pure substances that keep their own properties.

Question 12

What happens to solute particles when a solution is formed?

Answer 12

Solvent particles surround and carry away the solute particles, making them spread throughout the solvent.

Question 13

What is evaporation?

Answer 13

When liquid particles gain enough energy to break free from the surface and form a gas.

Question 14

At what point does boiling occur?

Answer 14

When liquid particles move so fast that they fly apart and form bubbles within the liquid.

Question 15

How does diffusion occur in gases?

Answer 15

Gas particles move in straight lines until they collide with others, eventually spreading evenly.

Question 15

What is condensation?

Answer 15

When gas particles cool, slow down, and stick together to form liquid droplets.

Question 16

What is diffusion?

Answer 16

Where particles of two gases/liquids mix evenly without stirring.

Question 17

Why does increasing temperature speed up diffusion?

Answer 17

Particles move faster at higher temperatures (spreading quicker).

Question 18

Why is diffusion slower in liquids compared to gases?

Answer 18

Because liquid particles are packed more closely together than gas particles.

Question 19

What is the effect of a gust of wind on diffusion?

Answer 19

It speeds up diffusion by pushing air particles across the room.

Question 20

How does temperature affect gas pressure in a flexible container?

Answer 20

Higher temperatures cause particles to hit the sides more frequently, increasing pressure and expanding the container.

Question 21

What happens to gas particles when cooled?

Answer 21

They slow down, hit the container less often, and cause the container to contract if flexible.

Question 22

How are solid particles arranged?

Answer 22

In a fixed, tightly packed structure, only vibrating in place.

Question 23

How are liquid particles arranged?

Answer 23

Close together but free to move past one another, allowing the liquid to flow.

Question 24

How are gas particles arranged?

Answer 24

Far apart with little to no attraction, moving freely in straight lines until they collide.

Question 25

What is the main cause of expansion in solids?

Answer 25

Increased vibration of particles with temperature.

Question 26

What role does attraction play in the state of matter?

Answer 26

It binds particles in solids, is weaker in liquids, and nearly absent in gases.

Question 26

How does mixing occur at the particle level?

Answer 26

Particles of substances mix evenly by spreading through each other, as seen in solutions and alloys.

Question 27

Why do liquids evaporate faster at higher temperatures?

Answer 27

Because particles gain more energy, allowing more particles to escape from the liquid’s surface.