Heat

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Heat

• Temperature – measured with a thermometer.
• Heat – is described as the thermal (kinetic) energy of all particles within an object.
• 2L of water at 100°C has more energy than 1L of water at 100°C . It has twice as many particles and therefore, twice as much heat energy.

1L of water will heat quicker than 2L because there are fewer particles. The particles each absorb more energy and move faster.

We compare different substances using Specific heat: amount of heat required to raise the temperature of a given mass of a substance.

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Water has a specific heat of 4.186 J/g°C

Iron 0.450 J/g°C

Aluminum 0.89 J/g°C

Granite 0.790 J/g°C

Graphite 0.710 J/g°C

Calculating the heat needed to raise temperatures….

Temperature

• Is an indicator of how hot or cold something is.
• Hotter substances have particles that are moving faster (more kinetic energy) than cooler substances.

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• Liquids expand when heated and contract when cooled – this is how a glass thermometer works.
• Temperature is measured in degrees Celsius °C, degrees Fahrenheit °F, and Kelvin K.

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Heat Transfer

• Heat flows from areas of higher temperature to areas of lower temperature.

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• The greater the temperature difference the faster the heat�flows from one�object to another.

Preventing Heat Transfer

• Insulation is a term used for materials that prevent (well slow it down) heat transfer.
• Different kinds of insulation are needed to prevent the different types of heat transfer

Conduction

• Is heat transfer by vibrating particles.
• Heat from warm objects melts ice.
• A hot mug transfers heat to hands.
• Conductors (e.g. copper wire) and insulators (e.g. rubber).

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Conduction

• Works in solids
• They have particles that when they vibrate are close enough to touch
• Good conductors have particles very close together�and tend to be smaller molecules or elements
• Poor conductors have particles that are not close together (for solids)

Convection

• When a fluid like air is heated the particles have more energy and move apart.
• Hot air is less dense than cool air – hot air rises.

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Convection

• Heat
• Expand
• Rise
• Cool
• Drop

Radiation

‪www.bbc.co.uk 

Radiation

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Why is this part

darker in color?

Hot air leaves

here, manages

to heat the

plastic

Why does the heat�get wider?

Radiation

• Radiation moves through empty space.
• Air and other gases are mostly empty space so Radiation can move through gases as well.
• Solids and liquids absorb radiation and convert it to either conduction or convection, well some of them do…

‪www.bbc.co.uk 

• Dark coloured objects are good absorbers of heat e.g. a black car.
• Light coloured objects reflect more radiation and heat slower.
• Clear materials such as glass transmit radiated heat.

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Heat Transfer in Homes