What should we already know? We are going to go over topics that we covered at Key Stage 3 and need to know for the next few topics.

Atoms and symbols All substances are made up of p______. The smallest p_____ that can take part in a chemical reaction is called an a___. Elements are substances that each contain only _______ of atom. The atoms of each element are represented by a symbol. Examples of symbols used for elements are O (used for ______), N (used for _______) and Cu (used for ______). articles article tom one type oxygen nitrogen copper AQA Science © Nelson Thornes Ltd 2006  2

More work on symbols Fill in the gaps in the table below. Name of element Symbol Chlorine Cl Carbon C Silver Ag Bromine Br Sodium Na AQA Science © Nelson Thornes Ltd 2006  3

How are the elements arranged? Answer: Using the Periodic Table Vertical columns are called ___________ and horizontal rows are called ___________. groups periods AQA Science © Nelson Thornes Ltd 2006  4

Elements, mixtures and compounds Elements – these are substances containing only ______________. For example, sodium is an element and is made up of sodium atoms only. Compounds – these are substances made up of two or more types of atom. These atoms are joined together chemically. For example, carbon dioxide contains carbon and oxygen atoms joined together by chemical bonds. one type of atom AQA Science © Nelson Thornes Ltd 2006  5

Mixtures – these are not pure substances Mixtures – these are not pure substances. The compounds and/or elements making them up are not joined chemically. For example, air is a mixture of gases like oxygen (an element) and carbon dioxide (a compound). AQA Science © Nelson Thornes Ltd 2006  6

Elements, mixtures and compounds, continued Classify the following substances as elements, mixtures or compounds. mixture compound element AQA Science © Nelson Thornes Ltd 2006  7

How do we name compounds? The rules are: If there are two elements present, then the name ends in –IDE. For example, the formula CuS represents the compound _________ide. If there are three elements present and the third one is oxygen, then the name ends in –ATE. For example, the formula CuSO4 represents _________ate. copper sulf copper sulf AQA Science © Nelson Thornes Ltd 2006  8

Naming compounds, continued Name the compounds in the table below. Formula Name AlCl3 CuO Fe2O3 CaSO4 CaCO3 MgBr2 NaNO3 Aluminium chloride Copper oxide Iron oxide Calcium sulfate Calcium carbonate Magnesium bromide Sodium nitrate AQA Science © Nelson Thornes Ltd 2006  9

Chemical reactions The substances that react are called the REACTANTS. The substances formed are called the PRODUCTS. REACTANTS PRODUCTS To represent chemical reactions we write word equations or symbol equations. AQA Science © Nelson Thornes Ltd 2006  10

Chemical reactions, continued Write word equations for the following reactions 1 When sodium is burned in oxygen, sodium oxide is formed. sodium (s) + oxygen(g) sodium oxide(s) 2 When solid calcium carbonate is heated, it decomposes into solid calcium oxide and carbon dioxide gas. calcium oxide(s) carbon dioxide(g) + heat Calcium carbonate (s) AQA Science © Nelson Thornes Ltd 2006  11

Does the mass change during a chemical reaction? The answer to this is ___. NO For example, when 56 g of iron reacts with 32 g of sulfur iron sulfide is formed. The mass of the iron sulfide formed is __ g. 88 When 48 g of magnesium is heated in oxygen, 80 g of magnesium oxide is formed. What mass of oxygen is needed to react with the magnesium? The answer is __ g. 32 AQA Science © Nelson Thornes Ltd 2006  12

Burning fossil fuels The three fossil fuels are: Coal, oil and natural gas. When the fossil fuels are burned in enough air they always form water and carbon dioxide. Carbon dioxide is a __________ gas and is linked to g____ w______. greenhouse lobal arming Write the word equation for methane (natural gas) burning in oxygen. methane(g) + oxygen(g) carbon dioxide(g) + water(l) AQA Science © Nelson Thornes Ltd 2006  13

The Reactivity Series Metals are arranged in order of how reactive they are. A more reactive metal will displace a less reactive one from its compounds. For example, zinc will displace copper from copper sulfate to give zinc sulfate plus copper. The word equation is: zinc(s) + copper sulfate(aq) zinc sulfate(aq) + copper AQA Science © Nelson Thornes Ltd 2006  14