Chemicals are grouped together because of common properties. Acids are a group of sour chemicals. When a food tastes sour, like lemon juice or vinegar, it usually contains an acid. Bases have the opposite chemical properties of acids and feel slippery or soapy. Bases, like baking soda dissolved in water, have no strong taste.

Scientists have developed a scale to indicate how acidic or basic a solution is. You can test how acidic or basic a solution is by using a pH probe. The scale begins at 1, which indicates a very acidic solution, to 14, which indicates a very basis solution. A solution that has a pH of 7 (half way between 1 and 14) is considered neutral. In this activity you will test varying amounts of lemon juice in water and baking juice in water to understand the pH scale. After creating your scale, you will test leaves from different trees to determine their pH.

Your challenge is to investigate how adding different amounts of lemon juice to water will affect the pH, or acidity, of the solution. You will be able to use the pH probe to assist in your investigation. In your group spend a few minutes discussing and designing a procedure to be shown to your teacher.

Go to "Investigation I".