Materials

Acids are a type of chemical with certain properties. They react with metals and bases. Acids are found in all sorts of everyday things, and are not as dangerous as the industrial grade acids you sometimes see in movies. Many fruits contain acid. Oranges and lemons contain citric acid, which is shown being mixed with water in the picture.

The gases around you every day, inside or outside, is called the air. You need to breathe air to stay alive.

Asphalt is the residue left from making gasoline from crude oil. It is very thick and sticky, and when it is mixed with gravel it is a good substance for making roads out of.

In some countries, asphalt is known as bitumen.

Barbed wire, or barb wire, is a type of wire usually used for fencing that has twists of sharp wire along its length. Barbed wire is most often used on fences that keep livestock like cows and sheep from escaping. The sharp barbs on the wire will hurt anything that tries to climb over it.

Barbed wire is not just used to keep animals in or out. Barbed wire was used extensively during war time to protect soldiers, and is also used around prisons to keep the prisoners in.

A beam is a long piece of wood or metal that is part of the support for a large structure like a building. Beams are laid horizontally and are supported by posts.

Bitumen is another word for either asphalt or tar, depending on what country you are from. It is used in making roads.

A block is a piece of wood, stone or another kind of masonry that is used to build things out of.

Blocks can be very big and used to make buildings from, or very small and used as a children's toy.

A block is also a word used to describe a lot of small places that you live, like flats or apartments, that are joined together into one building.

Block is also used to describe something that stops something else from happening, like when you have writer's block you can't have any good ideas.

A board is a piece of wood that is wide and long but quite thin. Boards are usually used to make floors from, or for cladding on walls.

Many houses have walls that are made out of bricks. Bricks are hard, rectangular objects usually made from clay. They are very heavy.

Traditionally a cable is a very strong, heavy kind of rope. In more modern times, a cable has come to mean a long cord made of strands of metal and coated with an insulator, which is used to carry electricity or electrical signals.