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.

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.

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.

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.

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