Equations and Chemical Reactions

Starter Activity Argon Sulfur Boron Carbon Magnesium Copper Zinc Lead Sulfur Hydrogen Mercury Boron Carbon Magnesium Calcium Iron Phosphorus Iodine Copper Gold Arsenic Zinc Nitrogen Helium Oxygen Potassium

Extension Task Which of the elements are gases? Hydrogen H Oxygen O Nitrogen N Helium He Argon Ar

Reactants and Products The chemicals we have at the start of a reaction are called reactants. When a chemical reaction takes place the atoms in these substances are rearranged to form new chemicals. The substances formed in a reaction are called products. Example: If copper oxide is heated with magnesium it will react to form magnesium oxide and copper. We can write this as a simple word equation: Copper oxide + Magnesium Magnesium + Copper Reactants (substances we started the reaction with), always go on the left. Products (substances formed during a reaction), always go to the right of the arrow. Word Equation

You need to… For each of the chemical reactions you need to: Highlight or circle the reactants in one colour and the products in another colour (don’t forget to colour in the key) Complete the word equation for each reaction

Reaction One Sam mixed together some eggs, milk and flour. When he heated them in a large pan they reacted to form a big pancake! Eggs + Milk + Flour Pancake Eggs + Milk + Flour Pancake

Reaction Two When Katrina dropped a lump of magnesium into a test tube of hydrochloric acid, the chemical magnesium chloride was formed. Katrina also noticed a gas being formed. When a lit splint was placed in the gas it made a squeaky ‘pop’ sound. Hydrochloric Acid + Magnesium Magnesium chloride + Hydrogen

Reaction Three Luke reacted a lump of calcium carbonate with some sulphuric acid. Two of the products formed were water and calcium sulphate. The other product formed was a gas that turned lime water milky. Sulphuric Acid + Calcium carbonate Water + Calcium Sulphate Carbon dioxide

Reaction Four Bradley heated some copper turnings with some sulphur powder very strongly in a test tube. He noticed that at the end of the experiment, there was a bluish colour left on the surface of the copper. Copper Turnings + Sulphur Copper sulphide

Reaction Five Chelsea was given some nitric acid and some iron oxide. She reacts these together and finds that she makes a solution of iron nitrate and iron water. Nitric Acid + Iron Oxide Iron nitrate + Iron Water

Reaction Six Milos put a brand new iron nail outside and studied it for several weeks. He noticed that gradually the surface of the nail became coated with rust. He read in a science book that the chemical name for rust is “iron oxide”. Iron + Oxygen Iron Oxide

Reaction Seven Shona was learning about photosynthesis. She looked on the internet and found that in this process, plants take in carbon dioxide gas from the air and water from the ground. Using energy from the sun they can turn these chemicals into a kind of sugar called glucose and the gas oxygen. LIGHT Carbon Dioxide + Water + Glucose + Oxygen

Reaction Eight Jourdan told Shona that plants and animals respire. In this reaction they use up glucose and oxygen and make carbon dioxide and water and release energy that they can use to stay alive. Glucose + Oxygen + Carbon Dioxide + Water + ENERGY

Balancing equations When we talk about chemical reactions we always refer to the reactants and the products. When we write these chemical reactions we can sometimes use the formula Oxygen = O

Balancing Equations BUT, we must make sure that what goes into a chemical reaction also comes out WE MUST BALANCE THE EQUATION Lets have a go…

Balancing equations Methane + Oxygen Carbon Dioxide + Water CH4 + 2O2 CO2 2H2O H H H O O O H C H O O C H O O H H O

Chemical equations Hydrogen Oxygen Methane Water Ammonia (NH3) Carbon dioxide

Chemical equations The coloured spheres represent different atoms and the plastic connectors are the bonds that join atoms together. . Carbon (C) atoms Hydrogen (H) atoms Oxygen (O) atoms Bonds Nitrogen (N) atoms Chlorine (Cl) atoms Sulphur (S) atoms

To be able to balance simple equations Balancing Equations To be able to balance simple equations

One carbon atom and two oxygen atoms react One carbon atom and two oxygen atoms react. How many atoms are in the product? C O O C

C + O2  CO2 C O O C

How Will Our See-Saw Look? C + Cl2  CCl4 Cl C C Cl

It’s a Bit Product Heavy C + 2Cl2  CCl4 Cl C Cl C Cl

Now everything balances! C + 2Cl2  CCl4 Cl C Cl C Cl

How will the see-saw look here? 4O2 + S8  8SO2 S O S O

4O2 + S8  8SO2 How can we change this? O S O S O S O S O S O S O S

8O2 + S8  8SO2 O O S = 8 O = 16 O O O O O S O S O O S O S O O S O S O

8O2 + S8  8SO2 O O O S O O S O S O O O S O O S O O S O S O O S S = 8

Ag + S8  Ag2S Balance This Equation Ag Ag = 1 S = 8 Ag = 2 S = 1 Ag S

Balance These Equations Fe + H2SO4  FeSO4 + H2 Mg + HNO3  Mg(NO3)2 + H2 Zn + HCl  ZnCl + H2 When you are done turn these into word equations.