Comparing Materials

• Materials have certain PROPERTIES which make them USEFUL

We need to be able to describe and compare the properties of a material and say why its used for a job. We use certain materials for certain jobs…

Steel Bridge

Plastic container

Metal hammer head

Diamond ring

Fishing rod

Leather belt

ladder Metal scaffolding

window

towelling Paper towels/tissues

Elastic band Stretch fabric

springs

Conductors and Insulators of Heat

1. Some Materials let Heat pass through them Easily

1) These materials are called THERMAL CONDUCTORS

2) METALS are good THERMAL CONDUCTORS

3) Because heat passes through them quickly – metal normally feels COLD

Some Materials Do Not let Heat pass through them

1) Materials that do not let heat pass through them are called THERMAL INSULATORS.

Wooden handle

Oven glove

thermals

2) Plastic, cork, wood and fabrics are good THERMAL INSULATORS

3) Thermal insulators are good for keeping heat OUT as well as IN

ThermosDoes both

Polystyrene cup – keeps

heat in

Fridge – keeps heat out

Conductors and Insulators of Electricity

1. Conductors let electricity flow through them

1)Materials that can carry electricity are called conductors – they conduct electricity

2) Metals like copper, iron, steel and aluminium are all good conductors.

Insulators do not let electricity flow through them

1. Materials that can not carry electricity are called insulators – they do not conduct electricity

2. Wood, plastic, glass and rubber are all insulators.

Insulators and Conductors both have important Uses

Wires are coated in plastic – electricity cant flow through it so you don’t get a shock if you touch it

Copper wire allows electricity to flow through

A plug has metal pins – conduct electricity, insulated flex and a plastic cover to hold

Electricity can be dangerous

You shouldn’t tough anything electrical with wet hands – and that includes switches.

Electricity can be conducted through sweat (salty water) to your body, giving you and electric shock

Remember – water conducts electricity