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Can you change the boiling point of water? L/O :- To plan a test, follow lab safety rules when doing a practical, graph results and write a conclusion.

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Presentation on theme: "Can you change the boiling point of water? L/O :- To plan a test, follow lab safety rules when doing a practical, graph results and write a conclusion."— Presentation transcript:

1 Can you change the boiling point of water? L/O :- To plan a test, follow lab safety rules when doing a practical, graph results and write a conclusion

2 Why do cooks put salt in the water when they cook pasta?

3 I think the salt is added to the pasta to make it taste better If you add salt to the water the water stays colder so the pasta cooks slowly Adding salt makes the water boil faster Adding the salt just makes them look like they know what they are doing – they are showing off!! I think the salt might increase the boiling point so the water is hotter

4 You are going to plan an experiment to test your ideas Planning an investigation Step 1 What are you investigating? Step 3 Control variables What variables do you need to keep the same to make it a fair test? Step 4 Choosing the resolution What scale of measurement are you going to use? Step 2 Independent Variable What are you going to change? Dependent Variable What are you going to measure? Step 6 Do you need a control in your experiment? Step 5 What equipment are you going to need? Step 7 What do you Predict will happen and why?

5 Recording your Results Design a table to collect your results in 1st2nd3rd Independent variable - the thing you change These are usually the things you have measured NEVER FORGET YOUR UNITS!!! (e.g. (s), (m), (cm), (N) Use a PENCIL and RULER

6 Conclusion – what do your results show? Did adding salt to water affect the boiling point? Are you results repeatable (did you repeat the test)? Are you results reproducible - did other people do the same or similar test – did you compare results?

7 Adding salt to water increase the boiling point In other words the water does not boil at 100  C, but instead >100  C (enough salt will cause it to boil at 105  C) This is all because the salt dissolves in the water, changing the water’s properties - more energy is required to turn the solute (the salt) into its gaseous state So the more salt you add, the higher the boiling point will be (until you hit a limit, where no more salt can dissolve)!

8 What did you find out? Are your results accurate? How do you know? Was your resolution appropriate? How do you know? You can get more accurate results by removing anomalies when calculating a mean. Did you use the smallest scale on your measuring instrument?


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