Section 2: States of Matter

Chapter 9:Heat and States of Matter

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• The particles of a solid are packed closely together and are constantly vibrating in place.

Four States of Matter

• The attractions between particles are strong and solids have a fixed volume and shape.

SOLID STATE

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• The attractive forces are strong enough to cause particles to cling together.

LIQUID STATE

• Liquids have a definite volume, but not a definite shape.

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• In a gas the forces between particles are so weak that the particles no longer cling together.

GAS STATE

• Gases do not have a definite shape or volume.

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• The most common state of matter in the universe is the plasma state.

Plasma State

• PLASMA is matter consisting of positively and negatively charged particles and does not have a definite shape or volume.

22States of MatterStates of Matter

• The temperature at which a solid begins to melt is its melting point.

Changing States

• The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point is known as the HEAT OF FUSION.

Melting

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• The HEAT OF FUSION is also the energy released when a liquid freezes.

Freezing

• The attractive forces are strong enough that the particles form an ordered arrangement.

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• Vaporization occurs as liquid changes into a gas.

Vaporization

• Vaporization that occurs at the surface of a liquid is called evaporation.

• Evaporation causes the temperature of the liquid to decrease.• Can you explain this?

22States of MatterStates of Matter

• The BOILING POINT of a liquid is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on its surface.

Boiling

• The HEAT OF VAPORIZATION is the amount of energy required for 1 kg of the liquid at its boiling point to become a gas.

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• The HEAT OF VAPORIZATION is also the amount of energy released during condensation.

CONDENSATION

• This graph shows the temperature change of water as thermal energy is added.

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• The average kinetic energy of the water molecules doesn’t change.

CONDENSATION

• The temperature remains constant during melting.

What about during evaporation?

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CONDENSATION

of the gas increases as energy is added.

• After the liquid water has changed completely into a gas, the temperature

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• The increased separation between the particles results in the expansion of the object and the size of the object increases.

Thermal Expansion

• When a material cools, the particles in the material move more slowly and become closer together.

THE THERMAL EXPANSION OF MATTER

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• The forces between the particles in liquids are weaker than the forces between the particles in a solid.

THERMAL EXPANSION OF LIQUIDS

• The same temperature increase usually causes liquids to expand much more than solids.

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• In a gas, the forces between particles are much weaker than they are in liquids.

THERMAL EXPANSION OF GASES

• Gases expand even more than liquids for the same increase in temperature.

22Section CheckSection Check

Question 1

_________ is a state of matter consisting of positively and negatively charged particles that exists where the temperature is extremely high.

A. GasB. LiquidC. PlasmaD. Solid

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Answer

The answer is C. Plasma is found in the Sun, stars, lightning bolts and neon lights.

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Question 2

Most __________ materials have a specific type of geometric arrangement.

A. gaseousB. inertC. liquidD. solid

22Section CheckSection Check

The answer is D. The particles in most solids align themselves in ordered geometric patterns.

Answer

22Section CheckSection Check

Question 3

The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point is known as the _______.

A. heat of energyB. heat of fusionC. heat of meltingD. heat of vaporization

22Section CheckSection Check

Answer

The correct answer is B. Heat of fusion causes an ice cube to become liquid water.