Heat Flashcards
Experiment to show solids expand when heated and contract when cooled.
This is shown in the ball and ring experiment.
Firstly, set up the equipment. The ball is put through the ring and it is able to go through. The ball is then heated. However, when we try to put it through the ring it does not fit, showing that it expanded. When we let it cool, it is able to go through the ring once again show that it has contracted.
What is heat? What is its unit?
Heat is a form of energy.
Unit of heat = joule. (j)
Experiment to show liquids expand when heated and contract when cooled.
Firstly, set up the equipment as show in the diagram.
Turn on the bunsen burner, and observe the water. After a while, you will notice the water going up the glass tube. This proves that it expands when heated.
When it is cooled, the water goes back down and out of the glass tube. This proves that it contracts when cooled.
Experiment to show gases expand when heated and contract when cooled.
firstly, set up the equipment as shown in the diagram.
Turn on the bunsen burner, and heat the air in the flask.
Bubbles then appear in the water, showing that gases expand when heated.
When it cools, the water then goes up the tube to fill up the empty space. (vacuum)
Methods of heat transfer
Conduction, convection and radiation.
What is conduction?
Conduction is the transfer of heat through a solid without the particles in the solid moving out of position.
What is convection?
Convection is the transfer of heat through a liquid or gas when the molecules of the liquid or gas move upwards to carry the heat.
What is radiation?
The transfer of heat in rays, from a hot object, without needing a medium (solid, liquid, gas) to pass through.
To show radiation
The temperature of water in both cans dropped due to heat loss by radiation.
The can with the dull black surface was a better radiator than the other can.
Heat travelled by radiation from the hot water in the cans
To show convection and conduction in water.
Set up the equipment as shown in the diagram.
Firstly, heat the top of the water.
The water at the top of the test tube can be boiling but the ice has not melted. Heat does not travel down the water.
• Water is a poor conductor of heat.
After that, let the ice cube float up and heat the bottom of the water.
Heating the test tube at the bottom results in all the water in the tube boiling.
• Heat travels in water by convection.
To show conduction
Heat travels along the rods. The pins fall off the rods as the wax melts. However, the first pin to fall off was stuck to the best conductor.
Heat was conducted along the rods. Some materials are better conductors than others.
Which of these are better at conducting heat? copper, brass, iron, aluminium.
Copper,
then aluminium,
then brass,
then iron..
To show convection
As the water is heated, convection currents start to flow in the water. The dye helps us to see these convection currents.
In conclusion, heat travels through water in convection.
What is temperature?
+ unit of temperature.
Temperature is the measurement of how hot or cold an object is.
It’s unit of temperature is degrees celcius.
It is measured using a thermometer.
Latent heat
Latent heat causes a change in state and not a change in temperature.
