HEAT

• Heat and temperature: how vigorously atoms are moving and colliding
• Three ways that heat energy can be transferred: conduction, convection, radiation

PHYSICAL CHANGE: ENERGY TRANSFER

• States of matter (solid, liquid, gas) in terms of molecular motion
In gases, loosely packed atoms and molecules move independently and collide often. Volume and shape change readily.
In liquids, atoms and molecules are more loosely packed than in solids and can move  past each other. Liquids change shape readily but resist change in volume.
In solids, atoms and molecules are more tightly packed and can only vibrate. Solids  resist change in shape and volume.
• Most substances are solid at low temperatures, liquid at medium temperatures, and gaseous at high temperatures.
• A change of phase is a physical change (no new substance is produced). • Matter can be made to change phases by adding or removing energy.
• Expansion and contraction

Expansion is adding heat energy to a substance, which causes the molecules to move more quickly and the substance to expand.

Contraction is when a substance loses heat energy, the molecules slow down, and the substance contracts.

Water as a special case: water expands when it changes from a liquid to a solid.

• Changing phases: condensation; freezing; melting; boiling

Different amounts of energy are required to change the phase of different substances. Each substance has its own melting and boiling point.
The freezing point and boiling point of water (in degrees Celsius and Fahrenheit)