How do you “recognise” the pH scale? What do you want the students to be able to do to show you that they “recognise” the pH scale? E.g. State that the pH scale ranges from 0 to 14 etc? Similarly, what do you expect students to be able to do when they understand what indicators are? E.g. state the colour changes when litmus is used to test for acid and alkali? Be more specific. The objectives need to be measureable.
After this lesson, you should be able to:
the pH scale
what indicators are
To measure the acidity or alkalinity of a substance
It is a range of values between pH 0 to pH 14.
pH < 7
pH > 7
HOW TO FIND OUT PH VALUES OF
-Electronic device to measure the acidity or
alkalinity of solutions accurately
- Comes with a pH sensor which will measure the
change in pH value of solutions over time.
- Connected to the computer to transfer the data
Acids turn blue litmus paper red
Alkalis turn red litmus paper blue
WHAT IS AN INDICATOR?
A substance which changes colour depending on
whether the solution tested is acidic or alkaline
They are usually solutions
Can come from natural sources or synthetic
pH 0 to pH 3: red
pH 4 to pH6: orange/yellow
pH 7: green
pH 8 to pH 10: dark green/blue
pH 11 to pH 14: purple
COLOUR CHANGES OF OTHER
pH 0 to pH 3: Orange to red
pH 4 to pH 14: Orange to Yellow
pH 1 to pH 9: Remain Colourless
pH 10 to pH 14: Colourless to Pink
What is the function of a litmus paper?
To test if a solution is an acid or alkaline.
When would it be more suitable to use the
Universal Indicator pH paper?
When you need to find out the exact pH of a