Unit 1 Lesson 6 Changes of State
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Unit 1 Lesson 6 Changes of State
The Fact of the Matter
What happens when matter changes
state?
• The three most familiar states of matter are solid,
liquid, and gas.
• A change of state is the change of a substance
from one physical form of matter to another.
• When a substance undergoes a physical change, it
does not change its identity, just its appearance.
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Unit 1 Lesson 6 Changes of State
What happens when matter changes
state?
• To change a substance from one state to another,
energy must be added or removed.
• When a substance gains or loses energy, its
temperature changes or its state changes.
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Unit 1 Lesson 6 Changes of State
What happens when matter changes
state?
• All matter is made of tiny particles that are in
constant motion. During a change of state, the
motion of the particles changes.
• Particles can break away from each other and gain
more freedom to move, or they may attract each
other more strongly and have less freedom to
move.
• During a change of state, a substance gains
energy from or loses energy to the environment,
but the total amount of energy is conserved.
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Unit 1 Lesson 6 Changes of State
What happens when matter changes
state?
• Where in this diagram do water particles gain
energy from the environment? Where do they lose
energy?
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Unit 1 Lesson 6 Changes of State
Solid Facts
How do solids and liquids change
state?
• The change in state in which a liquid becomes a
solid is called freezing.
• When a liquid is cooled, its particles have less
energy, they slow down, and they lock into the
fixed arrangement of a solid.
• The temperature at which a liquid substance
changes into a solid is the liquid’s freezing point.
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Unit 1 Lesson 6 Changes of State
How do solids and liquids change
state?
• When a solid is warmed, its particles gain energy
and speed up, and the attraction between them
decreases. Eventually they slide past one another.
• The change of state from a solid to a liquid is
called melting.
• The temperature at which a substance changes
from a solid to a liquid is called its melting point.
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Unit 1 Lesson 6 Changes of State
Bubbling Over
How do liquids and gases change state?
• As a liquid is warmed, its particles gain energy.
• Some particles gain enough energy that they
escape from the surface of the liquid and become
a gas. This process is called evaporation.
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Unit 1 Lesson 6 Changes of State
How do liquids and gases change state?
• A rapid change from a liquid to a gas, or vapor, is
called boiling.
• This change takes place throughout a liquid, not
just at the surface.
• The specific temperature at which this occurs in a
liquid is called the boiling point.
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Unit 1 Lesson 6 Changes of State
How do liquids and gases change state?
• How does evaporation differ from boiling? Which
of these processes is represented here?
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Unit 1 Lesson 6 Changes of State
How do liquids and gases change state?
• As a gas is cooled, its particles lose energy.
• The attraction between particles overcomes the
speed of their motion, and a liquid forms.
• This change of state from a gas to a liquid is
called condensation.
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Unit 1 Lesson 6 Changes of State
How do liquids and gases change state?
• What is happening to the water particles in each
image?
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Unit 1 Lesson 6 Changes of State
Into Thin Air
How do solids and gases change state?
• Under the right conditions, some solids and gases
can change state without ever becoming a liquid.
• The change from a solid state directly into a gas is
called sublimation.
• Deposition is the change in state from a gas
directly to a solid.
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Unit 1 Lesson 6 Changes of State
Conserve
What happens to matter when a
change of state occurs?
• When matter changes from one state to another,
its physical state changes but its chemical identity
does not.
• During a change of state, the energy of the
particles, their movement, and the distance
between them change.
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Unit 1 Lesson 6 Changes of State
What happens to matter when a
change of state occurs?
• The mass of a substance does not change when
its state changes.
• Each state contains the same amount of matter.
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Unit 1 Lesson 6 Changes of State
Gas Laws
The Pressure-Volume Relationship:
• Boyle’s Law: for a fixed amount of gas, at a constant
temperature, the volume of a gas decreases as the
pressure increases.
The Temperature-Volume Relationship: Charles’s
Law
• Charles’s Law: the volume of a fixed quantity of gas at
constant pressure increases as the temperature
increases.
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