Understanding Exothermic and Endothermic Reactions

Some chemical reactions can release energy.

These are called exothermic reactions.

When these reactions happen, they usually give off heat, which warms the surrounding area.

A common example is when you burn methane.

Here’s what happens during that reaction:

$\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} + \text{energy}$

This means that when methane burns, it creates carbon dioxide and water, while also giving off energy.

Another example of an exothermic reaction is respiration.

This is how our bodies create energy from the food we eat.

On the other hand, we have endothermic reactions.

These reactions work differently because they absorb energy.

When they absorb energy, the surrounding area gets cooler.

A great example of this is photosynthesis.

In photosynthesis, plants take in carbon dioxide and water, and then they use energy from sunlight to create food and oxygen.

Here’s the reaction:

$6\text{CO}_2 + 6\text{H}_2\text{O} + \text{energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$

This shows that when plants take in carbon dioxide and water with energy from the sun, they produce their food (glucose) and release oxygen.

To sum it all up:

• Exothermic Reactions: Energy is released, which makes the temperature go up.

• Endothermic Reactions: Energy is absorbed, which makes the temperature go down.