REVISIONyear 7

Elements, Compounds and Mixtures

THE ATOMConsists of three different units.

- Electrons (negatively charge and whizzing around the outside) - Protons (positively charged and in the nucleus) - Neutrons (no charge and in the nucleus)

Atoms combine to form molecules and compounds.

THE ELEMENTS

For example, magnesium + oxygen → magnesium oxide

Metal oxides are basic and solids

Non-metal oxides are acidic and gaseous

For example, carbon + oxygen → carbon dioxide

ELEMENTS REACTING IN OXYGEN

SOME KEY ELEMENTSThere are many elements that can be found on The Periodic Table. These are some key elements that you should know. But you should be familiar with the first 20 elements.

COMPOUNDSCompounds are formed when two or more different elements chemically combine. Compounds have different properties to the elements that combine to make them.

NAMING COMPOUNDSTwo elements joined together will have an -IDE ending More than two elements joined together with oxygen being one of them will have an -ATE ending

For example, iron + sulphur → iron sulphide

For example, copper + sulphur + oxygen → copper sulphate

iron + sulphur → iron sulphide

CLASS PRACTICAL

You need to recognise this reaction. It shows that a new substance is formed. Before the reaction iron is magnetic. Iron Sulphide is not magnetic and therefore proves a new substance has been formed.

Look at the observations made during this reaction.

H₂O

Chemical symbols are used to represent compounds. The numbers relate to how many atoms there are in the compound.

Conservation of mass states the mass of the reactants equals the mass of the products. For example, magnesium appears to gets heavier when heated in air because it chemically combines with oxygen to form magnesium oxide (Mg → MgO).

CHEMICAL SYMBOLS

water has two hydrogen atoms

water has one oxygen atom

MIXTURESMixtures are two elements or compounds that are together but not chemically joined.

(See separating substances section when complete)

→Dissolving is a good way to form a mixture. →Mixtures can be easily separated.

GLOSSARY Substance consisting of one type of atom. Substance consisting of two or more different elements chemically combined. A groups of atoms chemically joined e.g. water H₂O, oxygen O₂. Substance containing two or more elements or compounds that have not been chemically joined.

Element:

Compound:

Molecule:

Mixture:

POSSIBLE REVISION METHOD - SUMMARY CARDSSummary Cards contain the most important details of a topic. You should try to create a summary of the information, including key words, concepts and diagrams.

QUESTIONSIf you have revised the previous sheets effectively you should be able to answer the following questions without difficulty.

1. What three particles combine to form an atom? 2.What is the name given to the negatively charged particle in an atom? 3.Define an element. 4.Define a compound. 5.Define a mixture. 6.Where do you find non-metals on the periodic table? 7. Copper + Oxygen → 8.Copper + Sulphur + Oxygen → 9. Iron + Sulphur →

10. How can you tell that a reaction is occurring (or has occurred) between Iron + Sulphur in the production of Iron Sulphide? Give two reasons 11. How many carbon atoms are there in a molecule of Glucose?

QUESTIONSIf you have revised the previous sheets effectively you should be able to answer the following questions without difficulty.

C₆ H₁₂O₆

For extra information or help with revision use the

following pages in the KS3 CGP Study Guide, page

35 - 39.