HEAT SCIENCE

There are four phases of matter:

Phases of Matter

There are four phases of matter:

Phases of Matter

Animation

States of Matter

Solids: –  Are rigid, crystalline –  Hold their shape –  Have little translational motion of molecules

Solids have properties such as density and elasticity.

Examples:

Solids

Solids: –  Are rigid, crystalline –  Hold their shape –  Have little translational motion of molecules

Solids have properties such as density and elasticity.

Examples:

Solids

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?

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?

Liquids

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:

Gases

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?

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?

Temperature

Absolute Zero Freezing of Water Boiling of Water -273 °C 0 °C 100 °C -460 °F 32 °F 212 °F

0 °K 273 °K 373 °K

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)

Heat

Temperature

Temperature

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

Thermal Equilibrium

A thermometer reaches thermal equilibrium with

the material it is in.

When heat is transferred, it is pulled from hotter objects into colder objects. Three ways heat is transferred:

1.  Conduction 2.  Convection 3.  Radiation

Transfer of Heat

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

Conduction

Good conductors? Poor conductors?

Conduction

Good conductors? Poor conductors?

Conduction

Good conductors? Poor conductors?

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

Aluminium Copper

Iron Nickel Steel

Conduction

Good Insulators

Glass Plastic

Cardboard Paper

Chocolate

PRACTICAL: Comparing Conduction

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

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

Convection

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

Convection

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

Convection

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

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

Radiation

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

Radiation

ASSESSED PRACTICAL: Radiation

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.

Phase Change

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