Materials and their Properties

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…

strong Steel Bridge Plastic container

hard Metal hammer head Diamond ring

flexible Leather belt Fishing rod

Rigid Metal scaffolding ladder

transparent window

absorbent Paper towels/tissues towelling

stretchy Stretch fabric Elastic band

squashy springs

Conductors and Insulators of Heat Some Materials let Heat pass through them Easily These materials are called THERMAL CONDUCTORS METALS are good THERMAL CONDUCTORS 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. Oven glove Wooden handle thermals

Polystyrene cup – keeps heat in 2) Plastic, cork, wood and fabrics are good THERMAL INSULATORS 3) Thermal insulators are good for keeping heat OUT as well as IN Fridge – keeps heat out Polystyrene cup – keeps heat in Thermos Does both

A good insulator = a poor conductor

Heat travels from a warmer material to a colder one

Conductors and Insulators of Electricity 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 Materials that can not carry electricity are called insulators – they do not conduct electricity 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