Chemical Reactions

Have you ever taken a bite of a lemon and had your mouth pucker up because it was so sour? Have you ever wondered why some foods taste the way they do? One reason is because of things called acids and bases.

Lemons and other citrus fruits are filled with citric and ascorbic acids (vitamin C), which provide a wide range of health benefits. But they also make them taste sour.

On the other hand, some foods we eat are called bases. They are on the other end of the acid scale and taste bitter. Bases include items such as baking soda (to make baked goods rise), antacid tablets (to help against indigestion and heartburn), and some soaps.

acid: materials that taste sour, like lemon. If strong enough, these can burn your skin.

base: materials that taste bitter, like ground coffee. If strong enough (for example, ammonia or bleach), these can also be dangerous.

Fun Fact

pH is what scientists use to measure the acidity of a substance. A pH value of 7.0 is called neutral, while a value higher than 7.0 indicates a base. pH values lower than 7.0 indicate acids.

Here are some sample pH values for common foods:







Tomatoes (whole)




Sweet corn


White eggs


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