P1a 1.3 Conduction. Lesson Objectives To state that metals are good conductors of thermal energy. To list poor conductors or insulators. To explain why.

Task

Draw the particle arrangement for a solid, liquid and gas. Each diagram should have a maximum on 9 particles.

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solid liquid gas

Particles that are very close together can transfer heat energy as they vibrate. This type of heat transfer is called conduction.

What type of solids are the best conductors?

Conduction is the method of heat transfer in solids but not liquids and gases. Why?

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Conduction in MetalsAim: Testing conduction of heat in Metals.

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heat

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What happens when you heat a metal?

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Firstly – What is a metal?

Non-MetalsMetals

Sodium (Na)

Is a solid.

Na23

Sodium11

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A Closer Look Inside

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Element structure

Na23

Sodium

11Atomic Number – the number of protons and

electrons. (11p and 11e)

Mass Number – the number of protons and neutrons. (11p and 12n)

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Element structure

Na23

Sodium11

p n

The maximum number of electrons in each shell is 2, 8 and 8.

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Element structure

Hydrogen Helium Lithium

Carbon Nitrogen Oxygen

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Metals are good conductors of heat.

The outer electrons of metal atoms are not attached to any particular atom. They are free to move between the atoms – therefore are called FREE ELECTRONS

When a metal is heated, the ions vibrate more and the free electrons gain kinetic energy.

heat

This means that the free electrons move (diffuse) faster and transfer the energy through the metal through collisions with other free electrons and ions in the cooler region.

This makes heat transfer in metals very efficient.

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What about non-conductors?

These are called Insulators. Air is one of the best

Insulators (woolly jumpers)

Insulators have no FREE ELECTRONS.

They do not conduct heat as well as metals. Instead the atoms hold the electrons firmly in place.

Instead thermal energy is transferred through atom vibration instead (less effective).

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heat

ConclusionsMetals conduct heat better than non metals.

Copper is a better conductor than steel.

Wood conducts heat better than glass.

The transfer of heat is faster when the temperature difference is greater.

Remember: We know that metals are good conductors – think of a barbeque, you don’t touch the metal when it is hot!

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InvestigationUse different materials to insulate identical beakers of hot

water.

Control variables – amount of water, starting temperature, type of thermometer, same time period.

Try to explain what is happening in terms of type of heat transfer and particle theory.

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Are you now able to….

I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.