Choosing materials for a job

We choose a material because its properties suit the job. A window needs to be transparent, so we use glass. A pan needs to get hot without melting, so we use metal. A pan handle should not get hot, so it is made of plastic or wood.

Some jobs need several properties at once. A bridge must be strong and must not bend too much, so builders use steel and concrete. Small pieces can be put together to make a big object, like bricks in a wall. The same bricks can be taken apart and used to build something new.