Embedded Files
Objectives:
Know the meaning of indicator.
Know that the strength of acids and alkalis can be measured on the pH scale.
PART A
Read and copy this paragraph:
Different chemicals have different characteristics. For example in a lemon there is a chemical that makes lemon juice taste sour. Chemicals with a sour taste like this are called acids, there are acids also acids in other types of fruit and in vinegar. Some acids are stronger than others, the acid in lemon juice is safe to use in food and drink but you wouldn't want to taste car battery acid, it would cause chemical burns. It would be very dangerous to taste different chemicals so instead we can use indicators to tell if something is an acid. There is another group of chemicals called alkalis which can react with acids. Indicators can be used to identify alkalis too, for example litmus is an indicator which is red in acids and blue in alkalis.
Different chemicals have different characteristics. For example in a lemon there is a chemical that makes lemon juice taste sour. Chemicals with a sour taste like this are called acids, there are acids also acids in other types of fruit and in vinegar. Some acids are stronger than others, the acid in lemon juice is safe to use in food and drink but you wouldn't want to taste car battery acid, it would cause chemical burns. It would be very dangerous to taste different chemicals so instead we can use indicators to tell if something is an acid. There is another group of chemicals called alkalis which can react with acids. Indicators can be used to identify alkalis too, for example litmus is an indicator which is red in acids and blue in alkalis.
PART B
Watch the following video. You could try to make your own indicator at home by following the instructions.
ONLY DO THIS EXPERIMENT IF YOUR PARENTS ARE WITH YOU TO SUPERVISE AND THEY HAVE GIVEN THEIR PERMISSION.
PART C
Draw a results table for the next video experiment. It should have enough space for 8 different substances, what the colour was at the start and what the colour was at the end. Try to do it yourself but if you're getting stuck use this scroll down document for help.
PART D
Watch this video. This is another experiment with red cabbage indicator. Fill in the colour changes on your results table.
PART E
Copy this paragraph:
Some acids and alkalis are stronger than others. We can show this on the pH scale. Universal indicator is an indicator that changes to different colours depending on the pH number. The lower the number, the stronger the acid and the higher the number the stronger the alkali. Universal indicator is an indicator that changes to different colours depending on the pH number.
Some acids and alkalis are stronger than others. We can show this on the pH scale. Universal indicator is an indicator that changes to different colours depending on the pH number. The lower the number, the stronger the acid and the higher the number the stronger the alkali. Universal indicator is an indicator that changes to different colours depending on the pH number.
PART F
You can either copy or print out the outline of the pH scale below. Colour it in or write the names of the colours in the boxes.
pH scale.pngPART G
Write down the answer for each of the clues on paper and then work out the secret word.
cracking code 2.pngPART I
This is a fact file about acids and alkalis. Make sure you learn it - you might want to write it out or print it out. You could use it to make flash cards.
acid alkali facts.pngPART J
Try this quiz to finish.
End of lesson
End of lesson
Page updated
Report abuse