Lesson 3 - Now

1. Heating a material decreases the energy of its particles.

2. When you stir sugar into water, the sugar and water evenly mix.

Do you agree or disagree?

What do you think?

Lesson 3 Reading Guide - KC

• How can a change in energy affect the state of matter?

• What happens when something dissolves?

• What is meant by conservation of mass?

Physical Changes

Lesson 3-1

A physical change is a change in size, shape, form, or state of matter in which the matter’s identity stays the same.During a physical change, the matter does not become something different even though physical properties change.

Physical Changes

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Changes in size or shape are physical changes, the identity of matter has not changedExamples of changes in size/shape:Chewing food to make it smaller and easier to digestPouring juice in a glass changes its shape

Lesson 3-1

When thermal energy is added to a solid, the particles in the solid move faster and faster, and the temperature increases. When the particles are moving too fast for attractive forces to hold them tightly together, the solid reaches its melting point.

Physical Changes (cont.)

Lesson 3-1

When the particles in a liquid are moving so fast that attractive forces cannot hold them close together, the liquid reaches its boiling point.Sublimation occurs when a solid changes directly to a gas without first becoming a liquid.

Physical Changes (cont.)

Lesson 3-1As thermal energy is added to a material, temperature increases when the state of the material is not changing. Temperature stays the same during a change of state.

Lesson 3-1

When thermal energy is removed from a gas, particles in the gas move more slowly and the temperature decreases.

Condensation occurs when the particles are moving slowly enough for attractive forces to pull the particles close together.

After the gas has completely changed to a liquid, removing more thermal energy from the liquid causes particles move even more slowly.

Physical Changes (cont.)

Lesson 3-1

Freezing occurs when the particles are moving so slowly that attractive forces between the particles hold them tightly together.Deposition is the change from a gas directly to a solid.

Physical Changes (cont.)

Lesson 3-1Physical Changes (cont.)

How can removing thermal energy affect the state of matter?

Lesson 3-1Physical Changes (cont.)

How can removing thermal energy affect the state of matter?

Answer: Decreasing thermal energy can change a liquid to a solid or a gas to a liquid. For some substances, it can change a gas directly to a solid.

Lesson 3-1

Dissolving, or evenly mixing, is a physical change because the identities of the substances involved do not change.

Physical Changes (cont.)

What happens when something dissolves?

Lesson 3-1Physical Changes (cont.)

What happens when something dissolves?

Answer: One substance breaks into small particles that mix evenly throughout another substance.

Lesson 3-2

Conservation of mass refers to the fact that the total mass before and after a physical change is the same.

Conservation of Mass

Lesson 3 - VS

• During a physical change, matter can change form, shape, size, or state, but the identity of the matter does not change.

Lesson 3 - VS

• Matter either changes temperature or changes state when enough thermal energy is added or removed.

• Mass is conserved during physical changes, which means that mass is the same before and after the changes occur.

Lesson 3 – LR1

A. sublimation

B. dissolving

C. deposition

D. condensation

Which term describes what occurs when a solid changes directly to a gas without first becoming a liquid?

Lesson 3 – LR2

A. They move faster.

B. They move slower.

C. They stop moving.

D. Nothing happens.

When thermal energy is added to a solid, what happens to the particles in the solid?

Lesson 3 – LR3

A. different

B. greater

C. smaller

D. the same

Conservation of mass means that the total mass before and after a physical change is which of these?

Lesson 3 - Now

5. Heating a material decreases the energy of its particles.

6. When you stir sugar into water, the sugar and water evenly mix.

Do you agree or disagree?