How Do Microwaves Heat Water? The Science Explained Simply!

How do microwaves heat water? The simple answer to this question usually goes a little something like this:

Your microwave oven generates microwave radiation, which then agitates the water molecules contained in your food. This agitation creates heat, which is then spread throughout the food.

That simple answer does a pretty good job of getting the point across, but what’s really happening when you heat water in a microwave?

In the rest of this brief article, I’ll go into a little more detail. It’s not long, but by the end of it you’ll have a much deeper understanding of the science behind this simple answer!

The Physics Of Microwaves

Before explaining how microwaves heat water in particular, it’s worth going back to the basics of how a microwave oven works at all.

Your microwave oven generates – obviously enough – microwaves. This is a form of electromagnetic radiation which operates at a very high frequency.

Certain materials and compounds absorb these waves, while others are unaffected. Metals are a common example of what not to put in the microwave, as they reflect all of that energy back into the walls of the appliance.

As a result of this, they either heat up or they’re unaffected by the continuous bombardment of microwave energy.

Water Molecules & Polarity

How is water affected by a microwave oven though?

To understand this, it’s important to know that water molecules – just like many other types of molecule – have something called polarity.

Polarity simply means that the molecule has two or more areas of differing electrical charge.

In the case of a water molecule, there’s a negative pole provided by its oxygen atom. It also has a positive pole created by its pair of hydrogen atoms. 

Put them together and you’ve got…H2O!

Heating Water In The Microwave

Let’s move onto what exactly happens when you heat water in a microwave.

The field that’s generated by a microwave oven oscillates all the time. That means it changes its direction of positive and negative charge continuously.

This in turn means the water molecules in your food are constantly “spinning” in reaction to the changing nature of this wave. 

Remember, they themselves have a positive and a negative pole, and have to align with the changing electromagnetic field.

This behavior is known as dipole rotation, where the dipole part refers to the molecule having two poles.

As these water molecules are agitated, they create heat and this heat is then transferred throughout your food. 

That’s it!

Wrapping Up

I really hope I’ve explained that slightly more complex answer for you, in a way that’s easy to understand!