What are materials made of?
       4. Elements and compounds
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Atoms and molecules
Atoms are the building blocks of all materials, no matter how simple or complicated the material is. An element is made up of only one type of atom. Compounds are made up of different types of atoms combined together.

A lump of copper is made up of only copper atoms. Water particles are made up of hydrogen atoms and oxygen atoms combined together. Scientists call this type of particle a molecule.

Dictionary
Picture 4.8 How many different words are there in the dictionaries of all languages using the 26 letters of our alphabet? Almost too many to count.

How many compounds are there?
Whenever atoms from two or more different elements combine together we get a compound. There are more than 110 different types of atom. This is because there are more than 110 different elements.

There is, however, an almost uncountable number of ways of combining atoms of different elements together. That is why there is an almost uncountable number of different compounds.

Think about the number of different words we can make from just the 26 letters of the English alphabet. This will give you some idea of the number of different compounds that can be made from different arrangements of all the different atoms.

Many new compounds are identified or made every day. If you become a scientist, then you may make several new compounds yourself.

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Question 20
Look at the table below. There are some statements and some materials.

For each statement, decide whether it describes an element, a mixture or a compound and tick the box.

For each material, decide whether it is an element, a mixture or a compound. Then tick the box.

  element compound mixture
There was a chemical reaction when it was formed from two simpler materials.
It is made from atoms that are all the same.
It cannot be broken into a simpler form.
Sodium chloride
Brine
Water
Oxygen