10. Using resources (required practical 8 - water) Flashcards
1
Q
What is the practical investigating?
A
analysing a sample of water for purity and describing how to purify a sample of water using distillation
2
Q
Is potable water the same as pure water?
A
no
3
Q
What does pure water not contain?
A
dissolved solids, such as salts
4
Q
What are the steps for investigating if a given sample of water is pure?
A
- Check the pH of the water by placing a small amount of the water onto a piece of universal indicator paper
- Universal indicator is green if the pH is 7
- If the pH is not 7, then the water sample contains dissolved acids or alkali and is therefore not pure
- If the pH is 7, the water still may not be pure as it could still contain dissolved solids
- to check for those, first use a balance to weigh an empty evaporating basin and record the mass
- fill the evaporating basin with our water sample and place this on a tripod and gauze
- Use a bunsen burner to gently heat the water until it has all evaporated
- Allow the evaporating basin to cool and then weigh it again
- If the water sample contained any dissolved solids, then the mass of the empty evaporating basin will have increased
- If the mass of the evaporating basin increased, then the water sample contains dissolved solids and is not pure. If the mass did not increase, then the sample could be pure
5
Q
Why might the sample of water still not be pure after it having a pH of 7 and not having an dissolved solids?
A
it could still contain dissolved gases
6
Q
What are the steps for purifying water using distillation?
A
- First set up the correct apparatus
- Then gently heat the water using a bunsen burner, so that it boils gently
- The water will then evaporate and form steam
- The water vapour now travels along the collecting tube
- When the water vapour enters the cold test tube it condenses back into liquid water (this is now distilled water)
7
Q
What is distilled water?
A
Pure water
