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| Volume vs Temperature |
Pressure versus Volume: Quantitative Observational Experiment
Aim
To establish the relationship between the volume and pressure of a gas in a sealed container.
Prior Knowledge
- Fluids (pressure due to weight).
- Proportonal reasoning.
- Linear relationships.
Description of the Experiment
A tube, sealed at one end, is placed vertically with its open end submerged in a beaker of water, thus enclosing a volume of air in the tube. As the tube is lowered in the water, you can see that the water starts occupying the lower part of the tube. Your objective is to take data from the video and construct a rule relating the pressure and volume of the gas.
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Questions
Description: what did you observe in the experiment?
- How is the change in height of the water in the tube related to the change in volume of the gas?
- How is the depth of the mouth of the tube in the water related to the pressure inside the liquid?
- How is the depth of the mouth of the tube in the water related to the pressure of the gas inside the tube?
Explanation
Why do you think the volume of the gas changes as the tube goes down? Explain from a macroscopic and microscopic point of view. Using the data that you have collected, construct a rule relating the pressure and volume of the gas.
Testing
How can you test your explanation and the rule?
Experimental skills
What are sources of errors in this experiment (instrumental and systematic)? What is a difference between an instrumental and systematic error? What measurement gives you the greatest instrumental error? The greatest systematic error?
- Why is there no information on the initial volume of the gas in the tube?
- What can you do to avoid the affects of uncontrollable systematic errors when constructing a rule?
- How many variables can you apply this to?
- In this experiment, which variable do you think will be most prone to systematic error?
Maths skills
Which is a more specific statement: Direct proportionality or a linear relationship? ie: if x and y are linearly related, are they directly proportional? If x and y are proportional, are they linearly related?
If there are systematic errors in the data, can one establish a linear relationship or proportionallity?
