Can you change the boiling point of water? L/O :- To plan a test, follow lab safety rules when doing...
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Transcript of Can you change the boiling point of water? L/O :- To plan a test, follow lab safety rules when doing...
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
Why do cooks put salt in the water when they cook
pasta?
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
You are going to plan an experiment to test your ideas
Planning an investigation
Step 1 What are you investigating?
Step 3 Control variablesWhat variables do you need to keep
the same to make it a fair test?
Step 4Choosing the resolution
What scale of measurement are you going
to use?
Step 2 Independent
Variable What are you going
to change?Dependent
VariableWhat 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?
Recording your Results
Design a table to collect your results in
1st 2nd 3rd
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
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?
• Adding salt to water increase the boiling point
• In other words the water does not boil at 100C, but instead >100C (enough salt will cause it to boil at 105C)
• 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)!
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?