> The pH scale measures the acidity of things.

 

> The strongest acid is pH 0. Water is in the middle. It is pH 7, which is neutral. At the other end from acids are alkalis or bases. The strongest is pH 14.

 

> Vinegar is low on the scale (around 2).

 

> Other acids include: hydrochloric acid, Coca-Cola, citrus fruits, milk, and black coffee.

 

> Some alkalis include toothpaste, sea water, oven spray, cloudy ammonia, and caustic soda.

 

> Indicators can be used to show where something is on the scale.

 

> Some kinds of indicators include a universal indicator, which is a mix of indicators and changes colors according to pH (for example, 1=pink, 7=yellow, 14=blue), and litmus paper, which turns red or blue according to whether the substance is acid or alkali.

 

> Acids often dissolve things.

 

> Stomach aches can be caused by too much acid in your stomach. You can take medicine called antacid, which has a base in it, and that neutralizes the acid.