HEAT ENERGY AND ITS TRANSFER
Learning Points State that heat flows through a solid by conduction. Explain conduction in terms of vibrating particles. Know that metals are good conductors of heat energy.
Learning Points 4. State that a material which lets heat flow through it easily is a good conductor of heat 5. State that a material which does not let heat flow through it easily by conduction is an insulator of heat.
Which items are good conductors?
Conduction When heat travels by Conduction, the particles near the heat source start to vibrate. These vibrations are then passed to the atom next to them, which in turn pass the vibration through the material.
Learning objectives C – know that conduction is the transfer of thermal energy B – be able to draw a diagram showing conduction A – be able to explain the properties of thermal insulators and conductors
Heat Energy Conductors Metals are very good conductors of heat, which is why a metal spoon will get hot very quickly when used to stir the contents of a pan.
Design a Saucepan Challenge Holder on lid Handle Main part of pan Base Which parts of the saucepan do you want to get hot and which bits do you want to keep cool? Why?
Why does a pan get hot but the handle doesn’t? Why does the spoon get hot when you stir your tea? Why does a pan get hot but the handle doesn’t?
Quick conduction experiments Step up a clamp stand with four paperclips stuck onto a metal rod with vaseline. 2. Heat one end of the rod and time how long the paperclips take to drop off. www.abernet.org.uk
TIME TAKEN TO FALL OFF (S) Quick conduction experiments PAPERCLIP NUMBER TIME TAKEN TO FALL OFF (S) 1 2 3 4
Quick conduction experiments The heat from the bunsen burner has travelled along the rod by conduction. Can you explain what happened to the metal particles (or atoms) to allow the heat to move through the rod?
Conduction and Particles
How did the energy move along the rod? Remember that a solid is made up of particles. These particles are always vibrating.
Heating the rod As we heat the rod, the particles get more energy and vibrate more. They also bump into each other, passing some energy along.
The thermal energy is passed through the rod as the particles bump into each other. The entire rod eventually heats up. This is called conduction.
What is the best conductor? Place two different metal rods on a tripod stand so that they are touching at one end. 2. Stick a paperclip on the end of each rod using vaseline. 3. Heat the end of the rods that where they meet and time how long the paperclips take to drop off. www.abernet.org.uk
TIME TAKEN TO FALL OFF (S) What is the best conductor? TYPE OF METAL ROD TIME TAKEN TO FALL OFF (S)
What is the best conductor? The heat from the bunsen burner has travelled along both the rods by conduction. Can you explain why the conduction was faster in one rod and slower in the other?
Fill in the missing gaps on the sheet using the words in the box. Draw diagrams in the three boxes showing what happened as the rod was heated. Write underneath what is happening. Try and mention particles in your answer.
Good conductors in the home Stainless steel (mostly Iron) is a very good conductor of heat and is used to make cooking pots. denby.co.uk Can you think of any other items in your home that are good conductors?
HEAT ENERGY INSULATORS Wood is a poor conductor of heat. We tend to use wooden spoons in cooking since they won’t pass the heat through them onto your hand. We call Wood a good INSULATOR. kitchenaria.com
What is the best insulator? Place three different rods (metal, plastic and wood) into a beaker containing freshly boiled water. 2. After 5 minutes GENTLY touch the end of each rod and find out which ones are hot or cold. www.abernet.org.uk
HOT OR COLD AFTER 5 MINUTES What is the best insulator? TYPE OF METAL ROD HOT OR COLD AFTER 5 MINUTES
What is the best insulator? The heat from the bunsen burner has NOT travelled along some of the rods. Can you explain what happened to the particles in the INSULATORS that didn’t allow the heat to move through them?
Quick Quiz What is temperature a measure of? How can you make the temperature rise? What is the difference between “heat” and “temperature”? How hot or cold something is. Add heat energy Heat is the energy, temperature is how hot or cold something is.
Put these statements in order The neighbouring particles also move. Heat makes the particles vibrate. Particles in a solid are tightly packed together, so The heat can therefore travel along the solid. This movement means they have a higher temperature. 3 1 2 5 4
Fill in with “well” or “badly” A conductor lets heat travel _______. An insulator lets heat travel _______. Air lets heat travel _______ by conduction. well badly badly
Answer the questions Examples of conductors in the home are: Examples of insulators in the home are: Electric Iron, saucepan Pot handles, clothes
Finally… Imagine an alien has visited earth. They have asked you to explain what we mean by conduction. 2 minutes to think of your answer!