1. Indicators
8A1 – Thursday 26 Nov 2014

2. How can we tell if something is an acid or alkali?

3. Indicators
Indicators are chemicals that will change colour in the presence of an acid or an alkali
Litmus is a common indicator
Plants can also be used as indicators. Red cabbage, tea, and blackberry juice are all indicators

4. Set up your data table 1 2 TEST 1 TEST 2 Substance
TEST 1
TEST 2
Substance
Litmus Indicator Colour
Acid? Alkali? Neutral?
Universal Indicator Colour pH 1 2

5. Put it to the test! Procedure: Complete p. 16 in your workbook
Wear safety glasses
Dip the litmus indicator strip into the solution
Record the color on your data sheet
Decide if each solution is an acid, alkali, or neither (neutral)
Complete p. 16 in your workbook

6. H+ But Wait! Are all acids the same?
We measure how acidic something is using a pH scale
pH is a measure of the concentration of hydrogen ions in the solution H+

7. pH Scale
pH of common solutions

8. pH Scale •An acid a solution with a pH less than 7
•An alkali a solution with a pH greater than 7
•A solution with a pH of 7 is neutral
•A pH scale is used to describe how acidic or basic a solution is

9. pH test Universal indicator Procedure Complete WB p. 28
Repeat the tests from period 3 with universal indicator strips
Determine the pH of each solution
Record your results on your data sheet
Complete WB p. 28