Litmus

And I can prove it, too.

This is a strip of paper that's been infused with a chemical called litmus.

Litmus is a pH indicator, a chemical that turns different colors at different pHs.

There are many different indicators with many different colors, but we'll talk more about those next week.

For now, just know that litmus paper turns pink in acids, blue in bases, and a sort of light purple when it's neutral.