HEAT

Unit 7.1 : Heat As A Form of Energy

Sources of Heat• From the sun• From friction

Heat is produced when 2 surfaces rub against each otherExample: Rubbing our hands together

Engines of vehicle • From electricity

Heat is produced when electric current passes through a wire.Example: Electric kettle

Electric iron• From chemical reactions

Heat is produced in some chemical reactionsExample: Burning of fuels

RespirationMetal reacting with acids.

• From nuclear reaction A tremendous amount of energy is produced during nuclear fission and fusionExample: Nuclear explosion melts metals

• For keeping warm• For cooking• For producing light• For heating• For sterilizing• For making substances• For medical treatment• For melting and moulding

Uses of Heat

Properties of Heat

• Heat is a form of energy measured in units called joules (J).

• Heat can travel through solid, liquid, gas and vacuum.

• Heat travels from a hot place to a cooler place.

• Heat causes solid, liquid and gases to expand.

• Heat has different effects on different substances.

Heat and Temperature

Heat• Is a form energy

• Is measured using a formula involving mass of the object

• Unit of measurement for heat is Joules (J)

Temperature• Is a measure of

hotness or coldness of an object

• Is measured using a thermometer

• Unit of measurements for temperature are Celsius, Fahrenheit or Kelvin

100 ml water

100 ml water (60oC) 50 ml water

(60oC)

Experiment to show that heat and temperature is different.

• Aim:To show that an object of the same temperature may not contain the same amount of heatTo show that the amount of heat contained in an object depends on its mass.

• HypothesisThe greater the mass of an object, the more heat it will contain.

• Variables:Constant: Temperature of added waterManipulated: Volume/mass of added waterResponding: Final water temperature

• Observation: Temperature of water in the beaker that was added with greater volume/mass of water rises more than the water in the beaker that was added with less volume/mass of water.

• Conclusion:An object may have the same temperature but may contain different amounts of heat .The amount of energy contained in an object depends on its mass.The greater the mass of an object, the more heat it contains.

End of Unit 7.1