Name: ______Class: ______/20

Many common substances are either acidic or basic. In this investigation, you will use a natural pH indicator to find the pH of some common substances.

Question

What is the pH of a carbonated drink, and other common solutions?

Apparatus and Materials

·  100 mL beaker / ·  Red cabbage juice
·  Test tubes and rack / ·  Unidentified solutions to test:
·  100 mL beaker / o  Vinegar, distilled water, dilute ammonia, dilute hydrochloric acid, club soda, salt water, liquid egg white.
·  Glass stirring rod
·  Medicine dropper
·  pH paper

Safety Reminders

·  There should be no food or drink in the lab.

·  Gloves should be worn at all times, and long hair should be tied back.

·  Although many of the chemicals being used in today’s lab are ordinary household items, many have the ability to irritate your skin and eyes. Please handle all materials with care!

·  Make sure you remember to wash your hands at the end of the lab.

Procedure

1.  Add about 10 mL of vinegar into a test tube.

2.  Use a clean glass stirring rod to transfer a drop of the vinegar to a piece of pH paper. Compare the colour with the colours in the chart. Estimate the pH of vinegar, and record it in your data table.

3.  Use the medicine dropper to add a few drops of cabbage juice indicator to the vinegar. Record the colour of the indicator in the appropriate place in your data table.

4.  Repeat steps 1 – 3 for the remaining solutions.

5.  When you are finished, empty all of your test tubes into the waste bucket. Place the test tube that contained hydrochloric acid into the blue basket.

6.  Take all other test tubes to a sink and rinse them out. Wash your hands thoroughly with soap and water.

7.  Ensure all lab materials are put away, and then begin to work on the analysis questions on the back of this sheet.

Observations (1 mark)

Solution / Colour of cabbage indicator / Approximate pH range

Analysis

1.  Classify each of the substances that you tested as acids, bases or neutral. (6 marks)

2.  Why are the acidic/basic properties of a solution important to chemists? (1 mark)

3.  Other than substances used in the lab, name two household acids and their uses. (2 marks)

4.  Other than substances used in the lab, name two household bases and their uses. (2 marks)

5.  Label as either true (T) or false (F). (8 marks)

_____ 1. Acids will not conduct electricity

_____ 2. Bases will not conduct electricity

_____ 3. Acids taste bitter

_____ 4. Bases will turn red litmus paper blue.

_____ 5. An indicator is a substance which changes colours in acids and bases.

_____ 6. Acids will turn blue litmus paper red.

_____ 7. Bases feel slippery.

_____ 8. The pH of distilled water is 7.