There are four phases of matter: Phases of Matter

HEAT SCIENCE

Animation States of Matter

Solids Solids: Are rigid, crystalline Hold their shape Have little translational motion of molecules Solids have properties such as density and elasticity. Examples:

Liquids Liquids: Take the shape of the container they re in Have weaker intramolecular bonds than solids So molecules have a greater amount of translational kinetic energy Liquids have properties such as viscosity and are involved in buoyancy. How does buoyancy work?

Gases Gases: Take the shape of the container they re in (just like liquids) Have the weakest intramolecular bonds So molecules are very free for translational motion The atmosphere is made up of a number of gases:

Temperature Temperature: Measures how hot something is Depends on how quickly the particles inside it are moving Is a measure of average kinetic energy Hotter substances have particles that are moving faster than the particles of cooler substances. How do we measure temperature?

Heat What is heat? What is cold?

Heat What is heat? What is cold? Objects DO NOT have heat Heat: Is a transfer of thermal energy Is NOT TEMPERATURE Flows from hot objects to cold objects, just like how water flows How do we measure temperature? Joules (J) Calories (cal)

Temperature

Thermal Equilibrium When two objects are touching, heat will move from the hot object to the cold object until they reach thermal equilibrium. Thermal equilibrium = same temperature A thermometer reaches thermal equilibrium with the material it is in.

Transfer of Heat When heat is transferred, it is pulled from hotter objects into colder objects. Three ways heat is transferred: 1. Conduction 2. Convection 3. Radiation

Conduction Conduction is the transfer of heat along an object through touch or contact. Example: Heating up a pot of soup Need to pick it up with oven-mits/tea-towel because the handles get too hot to touch Heat energy travels from the base/sides of the pot to the handles

Conduction Good conductors? Poor conductors?

Conduction Metals have some electrons that are loosely bound to the atoms in the material. These electrons can move easily and can rapidly pick up additional kinetic energy. Wood and plastic don t have loosely bound electrons, so they are poor conductors.

Conduction Saying an object is an insulator is a fancy way of saying it is a poor conductor.

Conduction Saying an object is an insulator is a fancy way of saying it is a poor conductor. Which of the following are good conductors: Aluminium Glass Copper Iron Plastic Cardboard Nickel Paper Chocolate Steel

Conduction Good conductors Good Insulators Aluminium Copper Iron Nickel Steel Glass Plastic Cardboard Paper Chocolate

PRACTICAL: Comparing Conduction

Convection Convection occurs in all liquids and gases. Instead of having energy moved by collisions (like conduction), the fluid itself is set into motion called a current.

Convection Convection occurs in all liquids and gases. Instead of having energy moved by collisions (like conduction), the fluid itself is set into motion called a current. Example: Winds are convection currents in the atmosphere

Convection When a radiator heats the air, it becomes less dense and rises. Cool air moves in to replace the air that has risen. This generates air flow. Radiators don t need a fan to stir the air and distribute heat throughout a room. The rising air cools until it s density matches that of the surrounding air.

Convection

Convection Explain why breezes come from the ocean in the day and from the land at night.

Convection

Radiation Radiation is the process of heat transfer via electromagnetic waves. Example: Heat from the Sun!

Radiation Radiation is the process of heat transfer via electromagnetic waves. Examples of electromagnetic waves: Light waves Micro waves Radio waves X-rays

Radiation Every object emits electromagnetic waves regardless of temperature. Most objects emit infrared waves.

Radiation The hotter something is, the more heat it radiates. Example: Radiant heat of an oven when you open the door at a low temperature, compared to a hot oven Hot coals of an open fire

Radiation Radiated heat may be: 1. Absorbed into the surface 2. Reflected from the surface 3. Transmitted through the surface.

Radiation Explain why a dark-coloured car heats up more quickly in sunlight than a lighter-coloured car.

Radiation

ASSESSED PRACTICAL: Radiation

Phase Change When heat is added to, or taken away from a substance, the temperature of the substance will either increase or decrease. However, when a substance changes phase (ie: solid è liquid), heat is needed to change the properties of the substance.

Phase Change DID YOU KNOW? Solids can change phase to a gas (bypassing liquid form). This is called sublimation. Gases can also change phase into a solid (bypassing liquid form). This is called deposition.

Latent Heat Latent heat is the amount of heat required to change the phase of a material. Heat of Vaporisation: The heat required to change between a liquid and a gas Heat of Fusion: The heat required to change between a solid and a liquid

Phase Change