### The STEM Way

The STEM way is a learning and education blog for kids with STEM(Science,Technology,Engineering,Math) Lessons, Experiments, Worksheets and Quizzes for children.

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We use refrigerators to  keep our food cool .When food is kept cool, bacteria cannot attack and spoil the food.

#### How do these refrigerators work?

Lets understand the principle behind the working of the refrigerator.

Do you know that there are 3 states of matter, solid, liquid and gas. This means a substance can take 3 different forms depending on it’s temperature.

Lets take water as an example.

When the temperature of water is very very low- it becomes ICE- SOLID

At room temperature water is a LIQUID.

When we heat water to a very high temperature – it becomes a steam- GAS

### When a liquid becomes a gas it is called Evaporation.

Can you say Evaporation?

So what does a liquid need to become a gas? It needs heat!

It absorbs heat and evaporates.

#### Refrigerators works on this principle.

Refrigerators use a liquid that evaporates easily.

To evaporate it takes heat from it’s surroundings. So, as it evaporates it cools that area around it.

The gas is once again compressed to a liquid and the whole process is repeated again and again.

The liquid used in refrigerators is called HCFC (hydro chloro floro carbon). Let’s just call it the coolant. This is the substance that makes the refrigerator cold. It evaporates to a gas a very low temperature(-41 F)

STEP 1:

Have you seen the coils behind your refrigerator ? The coolant is in liquid state in these coils. The coolant flows to the expansion valve to expand.

STEP 2

As the Coolant expands it evaporates. Where does it get the heat to evaporate? It takes it from inside the fridge!

As it takes the heat it cools everything in the fridge!

You may have noticed this with an air freshener or a perfume. The perfume is stored as a liquid inside the bottle, as you release it it expands and becomes a gas.

STEP 3

For the Liquid to evaporate and become a gas it need heat. It takes this heat from it’s surroundings and cools down the whole refrigerator.

You can observe this with the perfume spray. It Feels Cool when you spray it! It is taking heat from the surroundings when it evaporates to a gas.

This is how your whole refrigerator cools down and keeps your food cool

STEP 4:

The gas is sent back to a compressor. The compressor compresses the coolant back to liquid state and once again it flows through the coils. This cycle keeps on repeating .

Ages: 4-5

ACTIVITY: Circle the things that you can put in your fridge

## Do you know how a refrigerator works?

MORE RESOURCES

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