3.22 To measure the acidity or alkalinity of substances

Natural sciences

Reactions that occur between different kinds of matter: acids and bases

Educator section

Memorandum

1. Coffee: Acidic (4 to 5)

2. Shampoo: Acidic (4 to 5)

3. Fruit salt solution: Acidic (0 to 3)

4. Tartaric acid: Acidic (0 to 3)

5. Lemon juice: Acidic (0 to 3)

Leaner section

Content

Activity: to measure the acidity or alkalinity of substances [lo 1.2]

A universal indicator uses a range of colours to indicate acidity or alkalinity. The pH scale is specially designed to enable us to make a decision about the degree of acidity or alkalinity of a substance. On this scale, the pH value of 7 is equal to neutral and values below 7 are acidic, while those above 7 are alkaline.

• The following illustration shows the approximate values of a number of household substances.

Use a universal indicator (a pH meter) to determine the acidity or alkalinity of the following substances:

1. coffee _________________________________________________________

2. hair shampoo ___________________________________________________

3. fruit salts solution ________________________________________________

4. tartaric acid _____________________________________________________

5. lemon juices_____________________________________________________

Assessment

Learning Outcome 1: The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

Assessment Standard 1.2: We know this when the learner conducts investigations and collects data: organises and uses apparatus/equipment or sources to gain and record information.