Heat can be transferred in 3 different ways. Conduction, Convection and Radiation. Draw the diagram below and leave space for the meaning of these words which will be in the video. This diagram will allow you to visualise what the 3 methods of heat transfer are.
E.g When you stand in front of a fire place, you feel the radiation of heat warming your body. You can also feel the air being warmed around you due to convection. If you touched metal above the fire place and it will burn you via conduction.
Heat Transfer Practical
Today’s practical will focus on all 3 forms of heat transfer and how some metals conduct heat quicker than others.
Our Bunsen burners get up to around 1500°C at the top of the primary flame, hidden within the outer flame. When we’ve used the tripods in the past you may have noticed that they get really hot even though they are not touching the flame and when doused in water they make steam.
NOTE: DON’T TOUCH THE METAL RODS WITH BARE HANDS, THEY WILL GET HOT!
You will be given a rod of different metals to place on top of your tripod.
Light a candle from your Bunsen burner.
Drip 3 evenly spaced wax drops onto your rod while they are cold.
Fan the rods out and make sure that they all meet at one end in the flame.
While the rods are being heated, time and observe when the blobs of wax begin to melt.
Copy the table below in your book (may need to add more rows) and answer the questions after test.
|Metal||1st blob||2nd blob||3rd blob|
- Describe what happened.
- Explain why you think this happened.
- What does it mean if something is a good conductor?
- Do you think the heat is transferred or transformed in the rods from the flame?
- Does all the heat energy from the flame conserve into the rods?
- What do you think would happen if you used a tree branch instead of metal?
- When you open a door in winter do you let the heat out or the cold in?
- If something is a good conductor of heat is it a good or bad emitter of heat?
- How do people get sunburn when they go to the snow?
- Why might dirty snow melt quicker than clean white snow?
- If you touch a hot piece of metal with a cold piece which way does the heat flow?
- Why does a lizard need to lay in the sun to warm up but you don’t have to?
- When it is hot outside and you have the A/C on inside, why should you keep the doors and windows shut?
- What are some things you can do in summer to keep the heat energy out?
Which colour is hotter? Practical
You’ve probably heard it before that Black cars get hotter in the sun than White cars. It even made Mythbusters many years back and has been retested in the video below.
Today though we are going to try and measure this ourselves. We will have a tin wrapped in foil and other that is left black with a thermometer in the top. Use the thermometer in the top to record the temperature over time. Record any extra observations below the graph.
|Time (min)||Black can (°C)||Foil wrapped can (°C)|