Science Teachers – 10 ideas for heat transfer lessons

A lot of students really struggle with the concepts of thermal energy transfer. It is a classic case of them turning up to our lessons having plenty of ideas of what is happening, most of which are wrong!

It may be worth looking at the Institute of Physics resources  (that include the new energy transfers which are not without controversy) here (You might have to register with www.talkphysics.org but it is well worth it as it has a superb forum and all the SPT materials )

iop warming

It is pointless trying to teach them the concepts until you really know what they are thinking so ensure you start with some AfL hinge questions. They will have covered this topic before so are we ready to move on?

Here is an example of a Science hinge question where the incorrect responses show typical student misconceptions:

The ball sitting on the table is not moving. It is not moving because:

A. no forces are pushing or pulling on the ball.

B. gravity is pulling down, but the table is in the way.

C. the table pushes up with the same force that gravity pulls down

D. gravity is holding it onto the table.

E. there is a force inside the ball keeping it from rolling off the table

Darren Mead @DKmead has written  a great explanation of hinge questions here

Some useful diagnostic questions are here (some are very high level but you can pick the appropriate ones )

transfer qs

Other useful questions to find out if they only know the definitions or really know how these mechanisms work

At certain times of the year the air temperature and the sea temperature are the same. If you get into the sea why does it feel colder? The truly brilliant Veritasium has a video for this

Other questions
Should ski/snowboard jackets be black or silver? How would we find out?
Are white china teacups a good design to prevent heat loss? How would we find out?

Use socrative @socrative , google forms or quizlet  here

Useful Practicals 

Before we start a practical  we really need to think what value it has to the learning. Too often practical activities can be a waste of time . A truly superb document to read is  here

http://www.york.ac.uk/media/educationalstudies/documents/research/Analysing%20practical%20activities.pdfDd

Observables and IdeasAnalysing Practical

I wouldn’t suggest filling in the form in the inventory available in the  appendix for every practical, but would suggest that you familiarise yourself with the key questions. 

Practical activities to support learning


Here are some ideas to draw out from them what they think in order to move them on. I take no responsibility for risk assessments or if they go horrendously wrong!

Sensing

the classic experiment to show how we sense temperature is with the hot and cold water

You can extend these ideas of sensing with these ideas

http://mps.uchicago.edu/docs/reports07/BrainBenders.pdfDd

Transfer from areas of high temperature to that of a lower temperature

This is a very simple experiment that works brilliantly with data loggers . I particularly like vernier ones as these are industry standard link here

http://www.inds.co.uk/education/labquest2.htm

This follows a simple script.

“I’m making a cup of coffee. I put the hot water in and am about to add the milk” ” Hang on a minute, my phone is ringing” Picks up phone ” it’s my mother, I can’t drink my coffee when she’s on the phone and the phone call will be at least 5 minutes long.” Pause ” Should I put my milk in now or in 5 minutes time to keep it as hot as possible?”

You can either do this as a thought experiment or for real . “There is the kit you may need, get on with it”

image

The rate of heat transfer depends on the difference in temperature of the two bodies. By putting the milk in straight away you reduce this temperature difference earlier. Hence milk in first stays warmer

 Ice cubes on a plastic and tin lids

Do ice cubes melt fastest on a tin or plastic lid – or does it not make any difference?

This is a great one to find students ideas using a simple AfL technique. If you think it would melt fastest on the metal lid put up your left hand, the plastic lid your right hand. No difference then hold up both hands.
Keeping their hands up they find someone who has a different opinion and argue with them until there is an agreement.

a nice Marvin and Milo card from the IOP here

(If technology is available this is an ideal activity to do with socrative short answers or on a padlet wall)

Balloons popping?
A very simple demonstration a balloon full of air pops ( make sure none of your students have a phobia!) the balloon full of water doesn’t. Why not?

image

http://www.physicscentral.com/experiment/physicsathome/balloon.cfm
Paper Kettle

A messy, fun and educational exercise.
The challenge is to boil 100ml of water in a paper kettle as quickly as possible. You must risk assess this before you do it

To make the paper kettles have the students fold a sheet of A4 paper in the way below Note: the heavier the paper used the better the result.

Once the kettles are made put them on a tripod with a gauze. Pour the water in and then move a Bunsen underneath. Give them a choice of how hot to make the flame (it’s fine on a blue flame) they may choose to use two kettles inside each other – mistake as air gets trapped and the paper will burn. They may choose to use another kettle as a lid.
Note: often there are spillages and fires so be prepared. They must not try to move the kettle on the gauze when it is wet as it will split.

Extension: Cook an egg in the paper kettle

This is smelly, messy and lots of fun do it in someone else’s lab or at the end of the day!

Convection – How can rice, a  table tennis ball and a ball bearing be used to demonstrate convection?
A very simple demo that students love. Push the table tennis ball to the bottom of the rice before showing it to the students. Then put the ball bearing on top. Shake the bowl vigorously and the ball bearing sinks. Continue shaking and the table tennis ball appears (and they love it!)
Why does this happen?

I’ll put a video of this up when I have time for now look at time  36 seconds

Effectively you turn the rice into a fluid and so denser objects will sink and less dense ones will rise.

Radiation

Students often confuse the concept of heat transfer by radiation (Infra-red) with the radiation emitted by radioactive nuclei.

Herschel experiment is a great one for showing that there is a part of the light spectrum we cant see that heats things up. A comprehensive outline is here 

Make a solar cooker here

Light a fire with a drinks can – this is awesome and works , but do a risk assessment!

Make your own drinks bottle solar panel

Give the students a plastic water bottle and a range of materials – who can make their water hottest?

Using all 3 heat transfer types

Solar Stills

One I use all the time.
I have been washed up on a desert island with 2 plastic bottles of water. I’ve drunk the water and then needed to go to the loo. Rather than waste my urine I’ve peed into a bottle.
Can you drink it? It looks ok, smells ok, tastes – sip some (it’s apple juice) ok!

Can now have a discussion as to whether drinking urine is ok

http://www.popsci.com/science/article/2011-03/fyi-it-ever-ok-drink-your-own-urine

Then give them
2 plastic bottles one half full of diluted apple juice
Tape
Cardboard, foil, paper, filter paper (red herring) black paper, newspaper etc

image
One solution is shown above. Effectively you create a mini water cycle with the aim of keeping the “urine” as hot as possible for evaporation and the other bottle as cool as possible For condensation.

Solar Still 2

Similar to above but this time have
Selection of trays, ice cream cartons etc
Plastic bags in a variety of colours including clear
Glass beakers
Stones
Dirty water/ ink
Filter paperer/silver foil

Have a competition to see who can produce the most clean water in a given time.

Solar still

Possible solution.
Though one group I did this with looked at the weather forecast which was for rain. As it was done outside they made a massive funnel and won!
Make a house to insulate a beaker of water

This is a wonderful practical to do to see whether students can apply concepts to come up with practical solutions. I have given this activity to groups who have ‘done’ heat transfer and  it is a perfect  activity to see who knows the names of the heat transfers from those who know how they work in reality. There is also no perfect solution. If you have access to mobile digital devices  get them to film their thinking.

They are given a sheet of A3 paper to make a ‘house’ with at least 3 windows that will keep a 100 ml beaker of water as warm as possible. There has to be a way of putting the beaker in the house ( or the house on the beaker) with a thermometer in it

A range of insulating materials are given, with one restriction. The total area of the insulating materials must fit onto a single sheet of A4 paper.

The area of insulation is the same

Materials can include: black paper (huge red herring) silver foil, carpet, bubble wrap etc

From the solutions you can deduce their thinking (or lack of)

Possible solutions

Many students create a traditional looking large house with big windows high up and a black roof to ‘absorb the heat’ shudder!! . Better solutions are to keep the surface area as small as possible – this also allows thicker insulation so a cylinder  with small windows low down and no black anywhere!!!

please feel free to add comments and  ideas

have fun!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s