Kinetic Theory and Gas Laws
The study of kinetic theory and the gas laws can present some conceptual challenges for students as they have to try and look at the relationships between gas properties on a macroscopic basis (P,V, T and m) as well as consider in places what is happening on a microscopic (particle) level. It's useful to make the distinction between the macroscopic and microscopic early in the teaching of these ideas so that students can become familiar switching between these with relative ease and confidence.
You could make two big signs labelled MACRO and MICRO to hold up when teaching this topic but less pantomime approaches to address the same challenge are possible.
This list contains lots of practical ideas here to help make this topic memorable and exciting for students
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance
Links and Resources
The collapsing can is more than just a good demonstration; it’s a great class practical so start saving those empty cans now. Using a clamp (the type normally used with clamp stands) around the top part of a can, students can hold the can directly in a Bunsen flame until they see plenty of steam coming out the top. Then turn the can upside down in a nearby washing up bowl of water for a very satisfying whoomp. Couple this experiment with the fountain experiment as recommended in this film to help students develop a deeper understanding of pressure. The accompanying teacher sheet contains useful teaching tips.
If you want to carry a new demonstration it’s so much better to have somebody show you how to do it than to have to read complicated instructions! Here is a series of films from Anu Ojha at the National Centre that will give you lots of good ideas for demonstrations and class experiments on the topic of pressure. They are simple to carry out, but striking and effective and it’s an added bonus that the class experiments are cheap too. Anu also explains the physics behind what he’s showing and teachers will enjoy his enthusiastic, expert delivery.
The student experiments with syringes and marshmallows and syringes and hot water are particularly recommended.
Films on the topic of pressure are:
• Pressure introduction – self explanatory
• Bell jar boil : a demonstration using a vacuum pump to boil warm water plus a student activity performing the same experiment in a syringe
• Bell jar: a demonstration using a vacuum pump to expand marshmallows by lowering the pressure
• Syringe marsh: a class activity using a syringe to expand marshmallows by lowering the pressure
• Water cup: classic experiment turning a cup of water upside down without spilling it
• Mars pressure suit: an exploration of the effect of low pressure on human anatomy
What’s titled “Boiling Water Without Heating Worksheet” is background information rather than a worksheet for students.
This series of experiments would make a good introduction to more quantitative work.
This is an impressive demonstration; making fire is always good fun and here it’s kinetic theory in action. Teachers new to the subject will appreciate both of the clear explanations offered by Alom Shaha and be able to base their own explanations around them. The kit is relatively easy to put together if you have confident technicians but the piston can be bought easily and reasonably cheaply too.
Experiments/demonstrations 71 (pdf page 170), 72 (pdf page 172) 75a (pdf page 178) use a kinetic theory model to help students to visualise gases. Many physics departments will already possess such a machine but if not they can be purchased relatively cheaply from school suppliers.
A good technique after showing students the machine in operation is to ask them to criticise the model, “In what ways is this a good model of a gas? In what ways is this an inaccurate model?” Don’t forget to allow time for thinking and don’t be too quick to jump in after students have answered, rather let them respond to each other’s ideas.
The Boyle’s Law apparatus shown in demonstration 76 (pdf page 181) is very visual and the data collected can be plotted by the whole class. Most equipment has the tube calibrated in volume rather than length so volume can just be read from the scale. Encourage students not just to predict the relationship between volume and pressure (as one goes up the other goes down) but to be more quantitative and to also predict the shape of the graph they will obtain.
You can find more recently published guidance on this topic from the IOP on their website here http://www.nuffieldfoundation.org/practical-physics/boyles-law