What is heat?

What is heat?

• Heat is a means of transferring energy between two bodies that are at different temperatures. 

 

• When two bodies with different tempereatures are in contact, there is a transfer of energy from one body to anoher. 

  

  ice cubes transfer cold to human body

  

  hot water transfer heat to the egg

   The effect of heat on matter

  Bodies which receive energy in the form of heat, can change its size or its state.
  
  

  Changes in size: 

  Depends on the temperature it is exposed to, the same object shrinks or expands.
  
  
  1.- Body size increases when it is heated (THERMAL EXPANSION) 
  
  
  
  
  ——2.- Thermal contraction takes place when the body cools down.

Change in state:

Matter is found in one of the following states:

Solid

Liquid

Gas

When it is heated, it can change state.

 Liquid + Cold = Solid (solidification)

Solid + Heat = Liquid (melting)

 Liquid + Heat = Gas (evaporation)

Gas + Heat = Liquid (condensation)

A simple heat experiment

Supplies you will need:

3 clear jars

water

food coloring

masking tape

markers

thermometer

1.-Label the jars with the temperatures you are going to use in the experiment.

Bottle 1:  as Cold Water

Bottle 2: as Room temperature Water

Bottle 3: as Hot Water

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2.- Add a drop of food coloring to each of the jars and observe what happens:

What happens to the drop of food coloring?

Does the food coloring behave the same in each of the jars? Why or Why not?

Molecules move faster when they are warmer and slower when they are colder.

The food coloring spreads out fairly quickly in room temperature water and slowes in the cold water.

Other heat experiment

To make the experiment you need:

Small plastic cup
Large bowl
spoon or stir stick
straws 
ice (lots!!!)
Salt (coarse rocks salt works best for this experiment)
Juice. We use Guava Juice, but you can use the juice you prefer.

1.- Set your plastic glass in the centre of your bowl filled with your juice, then add the ice all around the outside until the ice covers at least 3/4 up the side of the glass.
Carefully sprinkle salt on the ice. Be very careful not to get any salt in the juice. This is very important! but cover the ice with salt.

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2.- Now you should wait over 30 minutes. The juice will start to thicken up and once it reaches the desired thickness....it is ready to drink 😏

In this experiment we are applying the principles of heat transfer and the effect of salt on ice.

The salt causes an endothermic reaction that pulls heat from around it to melt the ice. It does this so aggressively that it will drop the temperature around it below freezing which allows our drink to go below freezing.

That is the reason why salt is thrown on the roads when it snows. The snow is melting and trafic accidents are avoided.

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