4.1 Heat

4.1 What is Heat?

• Heat is a form of energy that you can sense through receptors in your skin.
• Heat is a form of energy and describes the total energy of all particles within an object.
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Heat and Temperature

• Heat and temperature are both very different things.
• Temperature indicates how hot or cold something is. This depends on how quickly the particles inside it are moving and is a measure of the average kinetic energy of these particles.
• Hot= faster movement
• Cold= slow movement
• Temperature can be measured by a thermometer. An idea of the temperature can be identified by the receptors on the skin. Liquid expands when it is hot and contracts when cooled.
• 3 types of ways it can be measure: Celsius, Fahrenheit and Kelvin

Heat Transfer

• Heat flows from an area of higher temperature to areas of low temperature. The greater the temperature difference the faster heat flows from one object into another.
• This happens in 3 ways:
• -Conduction
• -Convection
• -Radiation
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Convection

• As air is heated, its particles gain energy and move further apart. Hot air pushed up and cold air is pushed down.
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Conduction

• Areas of high temperature flow towards areas of low temperature. This is a bit like diffusion.
• Hot substances have particles that move fast. These particles touch other particles and those particles touch other particles around it. This is how heat travels.
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Insulators and Conductors

• Insulators are materials which are poor conductors of heat.
• Examples:
• -Plastic
• -Rubber
• -Cloth
• -Wood
• -Cotton
• -Porcelain
• -Glass
• Conductors are substances that transfer heat easily. Most metals are good conductors.
• Examples:
• -copper
• -Aluminium
• -Gold
• -Silver
• -Water
• -People and Animals
• -Trees

Insulators and Conductors

Radiation and Colour

• The hotter something is, the more heat it radiates.
• When radiated heat hits a surface, the heat may be transmitted, absorbs or reflected off the surface. This is usually dependant on the material or colour.
• Dark Colours- ABSORB
• Light Colours- REFLECT
• Clear/Transparent- TRANSMIT
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Colours