•Defined shape•Defined volume•Fixed Particles tightly packed•Particles vibrate in their places

•Defined volume•Takes the shape of the container•Particles always touching but moving freely

•No defined shape•Takes the volume of its container•Particles spread out•Particles move rapidly and bounce off each other & walls of container

Phase Changes in Matter

• A phase change is the reversible physical change that occurs when a substance changes from one state of matter to another.

• Energy is either absorbed or released during a phase change.

Matter changes whenever energy is added or taken away.

• When something is heated, it gains thermal energy.

• When something is cooled, it loses or transfers energy.

• Many physical & chemical changes involve heating or cooling.

Law of Conservation of Energy

• States that “In EVERY physical or chemical change, the total amount of energy stays the same.”

• Remember: energy can change forms, but energy can NEVER be created or lost.

Changes in Between Liquid and Solid

• Melting and Freezing.• Melting- change in state from solid to liquid,

energy is gained in this process.• In most pure substances, melting occurs at a

temperature that’s specific to the substance, called the melting point.

• Ex. Ice cube taken from the freezer. The energy to melt it comes from the air in the room.

Melting (solid → liquid)

• The added energy from the room’s air, causes the water particles to move faster, this raises the temperature.

• Then when the melting point is reached, the water particles break free from their fixed positions, temperature stops increasing, and the particles arrange as a liquid.

Freezing (Liquid → Solid)• Changing state from a liquid to a solid.• Involves loss or transfer of energy.• Ex. Putting liquid water into the freezer.

The water loses or transfers heat to the cold air inside the freezer.

• The water particles them move more slowly, this means that the temperature is dropping.

• The particles become closer together and become fixed in position.

Changes in States Between Liquid & Gas

• Vaporization (2 types: evaporation & boiling) & Condensation.

• Vaporization- changing from a liquid to a gas.• Evaporation- a type of vaporization that takes

place ONLY on the surface of the liquid.• Ex. Of evaporation is a puddle drying up after

a rain.• Evaporation happens because the energy the

particles gain from the ground, air, or sun allow them to move faster, spread out, & change to a gas.

Evaporation- a type of vaporization, takes place ONLY on the surface of

liquid

Vaporization (Liquid → Gas)• 2nd type of vaporization, is boiling.

• Boiling- takes place inside a liquid as well as on the surface.

• Each liquid boils at a certain temperature- called the boiling point.

Condensation- (Gas → Liquid)• Is the opposite of vaporization.

• Condensation is when a gas loses or transfers enough thermal energy to become a liquid.

• Ex. Breathing onto a mirror. Air from inside you, transfers energy to the room and mirror. The particles slow down, get closer and arrange themselves as a liquid.

Changes in State Between Solid & Gas

• Have you ever noticed how snow seems to disappear even when the temperature stays well below freezing? This is due to sublimation.

• Sublimation- (Solid → Gas) occurs when the surface particles of a solid gain enough energy to become a gas, WITHOUT becoming a liquid.

• Ex. Dry ice (solid carbon dioxide) gains energy and turns directly into a gas.

Sublimation (Solid → Gas)

• Normal ice will also undergo sublimation.

• Ex. Ice left in an ice tray for a long time gets smaller because the surface particles gain enough energy to change into a gas.

• Where do you think the energy comes from?