Chemistry Notes <3

Compounds and Mixtures

All substances are made up of small particles called atoms. If a substance is only made up of one type of atom, it is called an element. Elements cannot be broken down into anything smaller using a chemical reaction.

There are only 92 different elements that you can find naturally on the Earth. Atoms of these elements join togeather, to make millions more kinds of substance. These substances are formed when two or more elements are chemically joined together and they are called compunds.

Many elements are well known such as Oxygen, Iron and Copper, but some elements are extremely rare, such as Samarium.

COMPOUNDS

Sodium chloride is a compound made from the elements Sodium and Chlorine. When these two meet they react violently to make the element sodium chloride. It is a substnce made from two different kinds of element, so its a compound. Sodium chloride is salt, and you know that it is a chemical reaction because salt is very different from both sodium and chlorine. Compounds are always very different from the elements that they came from.

We can describe what happens in a chemical reaction between two elements by writing a word equation. In a word equation, the reactants are shown on the left side, an the result on the right. There is always an arrow in between.

Sodium + Chlorine -> Sodium Chloride

Reactants Product

MIXTURES

An element is made up os identical particles, which are all made up of the same atom. A compound is also made up of identical particles, bue all of them have the same amount of different kinds of atoms that are chemically joined togeather. Mixtures are made up of more than one substance, and, as a result, many different kinds of particle. A mixture is a mixture of:

- Elements

-Compounds

-Elements and Compounds.

Sea Water is a mixture. It contains different solids, called salts, which all dissolved in the water. There is an average of 40g of salts in every kg of sea water, but there are an avaeage of 370g of salts that have been dissolved in every kilo in the Dead Sea. The Dead Sea is the worlds saltiest natural lake, and it is a mixture that is one of the worlds greatest sources of minerals. Over 43 billion tonnes of salts are thought to be dissolved in the Dead sea.

MOLECULES

When two or more atoms are chemically joined together. They can be different or the same, and if they are the same they are an element but if they are different they are a compound.

Metals

Metals all have some things in common, such as:

-Have high melting points, so are solid st room temperature.

-Are shiny when polished.

-Are dense.

-Can be hammered and bent into shape, and are usually tough and strong.

-Only three metals are magnetic, IRON, NICKEL and COBALT.

- Form mixtures of metals called alloys.

-Have alkaline oxides.

-Are good conductors of electricity.

Although metals have…