Acids and Bases

Our Unit Standard

7.P.2

The student will

demonstrate an understanding

of the structure and properties of

matter and that matter is conserved as it undergoes changes.

Today's Learning Objective

7.P.2B.3

Students will be able to

analyze and interpret data

(pH levels and properties)

to classify solutions as acids or bases.

Solutions can be classified as acids or bases depending on their chemical and physical properties and their pH levels.

• Physical properties can be observed without changing the composition of the substance.

• Chemical properties can only be observed by changing the composition of the substance, forming new substances.

• pH is the measure of how acidic or basic a solution is

Litmus paper

• Has a special dye on it that changes colors in the presence of an acid or base.

• Blue litmus paper turns red in an acid, and stays blue in a base.

• Red litmus paper turns blue in a base, and stays red in an acid.

Phenolphthalein

• Is used to test for the presence of a base.

• It is a colorless chemical that turns magenta (bright pink) in a base.

• It stays colorless in neutral or acidic solutions.

pH paper

• Has a range of colors depending on the pH of the solution.

• The color of the paper is compared to the chart on the vial to determine the pH.

Multiple Choice

When I put litmus paper in an acid such as vinegar, what color will the paper become?

• Blue

• Red

Multiple Choice

Bleach is a very strong base. When I put litmus paper into bleach, what color will the paper turn?

• Blue

• Red

Multiple Choice

If drain cleaner is added to phenolphthalein, what color would it become?

• red

• blue

• magenta

• violet