do now! don’t forget you have a digestion test on friday. do some study whilst you are waiting
TRANSCRIPT
Do now!Don’t forget you have a
digestion test on Friday. Do some study whilst you are
waiting.
Last lesson
Making and investigating indicators
Making an Indicator
Substance Colour (neutral)
Colour with acid
(HCl)
Colour with alkali (NaOH)
A good indicator?
Red cabbage purple red green Yes!Beetroot purple purple purple No!
Coffee brown brown brown No!
Today’s lesson
• Measuring the strength of acids and alkalis
• The pH scale
• Using “Universal Indicator”
The pH scaleThe strength of an acid is measured on the pH scale
pH stands for the “potential of hydrogen”
The pH scale
pH stands for the “potential of hydrogen”
strong acid
weak acid
weak alkali
Strong alkali
Universal Indicator
Universal Indicator
To measure pH, we need an indicator that has a different colour for each value of pH
Universal Indicator
Universal Indicator
It comes in the form of a paper
Universal Indicator
It also comes in the form of a liquid
Measuring pH
You are now going to measure the pH of various acids, alkalis and household liquids.
Measuring pH
Substance Predicted pH
Colour of Universal indicator
Actual pH