© OUP: To be used solely in purchaser’s school or college 8F Compounds and mixtures Element or compound Mixtures 8F Compounds and mixtures Changing state

© OUP: To be used solely in purchaser’s school or college Element or compound 8F Compounds and mixtures

© OUP: To be used solely in purchaser’s school or college 8F Element or compound – how are they different? Decide if these statements describe an element or a compound. contain only one type of atomsodium chloride is an examplethere are just over 100 different typescan be broken down into their separate elementscannot be broken down into anything smallercontain more than one type of atom that are chemically joined there are millions of different typeshydrogen gas is an example

© OUP: To be used solely in purchaser’s school or college 8F Element or compound – how are they different? Check your answers. contain only one type of atom sodium chloride is an example there are just over 100 different types can be broken down into their separate elements cannot be broken down into anything smaller contain more than one type of atom that are chemically joined there are millions of different types hydrogen gas is an example Elements Compounds

© OUP: To be used solely in purchaser’s school or college 8F Fabulous formulae A chemical formula can be very informative. It shows the numbers and types of elements in a compound. What is the formula of the compound described by these compositions? One copper to one oxygen One carbon to two oxygen One calcium to one carbon to three oxygen CuO CO 2 CaCO 3 Hydrogen and oxygen in the ratio 2:1H2OH2O Carbon and hydrogen in the ratio 4:1CH 4 Potassium, nitrogen and oxygen in the ratio 1:1:3KNO 3

© OUP: To be used solely in purchaser’s school or college 8F Comparing properties Does a compound have the same properties as the elements it is made of? SubstanceAppearanceIs it magnetic?Reaction with hydrochloric acid ironshiny metalyesbubbles - hydrogen gas sulphuryellow powdernono bubbles iron-sulphur mixture shiny metal + yellow powder only the iron is attracted to the magnet bubbles from the iron only – hydrogen gas iron sulphidebrown solidnobubbles – not hydrogen gas

© OUP: To be used solely in purchaser’s school or college 8F Comparing properties The word equation for the chemical reaction between iron and sulphur is Compare the particles of the elements, the mixture and the compound. Why does iron sulphide have different properties to the elements it is made of?

© OUP: To be used solely in purchaser’s school or college 8F Signs of a chemical reaction How do you know when a chemical reaction is taking place? colour changes gives out a gas cools down produces a solid glows heats up produces smoke flashes

© OUP: To be used solely in purchaser’s school or college 8F Compounds in chemical reactions Compounds can be the products of chemical reactions but can they also be reactants? Take a look at these chemical reactions and match the reactants and products. hydrochloric+magnesium acidcarbonate copper+carbon oxidedioxide sodium+iron carbonatechloride carbon+water copper carbonate iron+sodium carbonatechloride sucrosecarbon+water+magnesium dioxidechloride iron+sodium carbonatechloride copper+carbon oxidedioxide carbon+water

© OUP: To be used solely in purchaser’s school or college 1. In an element, the atoms are all the same. 2.A compound contains atoms of different elements joined together. 3. Carbon is a compound. 4. Elements in a compound are easy to separate. 5. A chemical formula shows what elements are in a compound. 8F Element or compound? True or false? TRUE FALSE TRUE

© OUP: To be used solely in purchaser’s school or college Mixtures 8F Compounds and mixtures

© OUP: To be used solely in purchaser’s school or college 8F Is it pure or impure? What is a mixture? A pure substance is not mixed with anything else. A material that contains more than one substance is ‘impure’. A mixture contains more than one substance mixed up, but not chemically joined, so they can be separated. So mixtures are impure. Is mineral water pure? Is tap water pure? How would you describe pure water?

© OUP: To be used solely in purchaser’s school or college 8F Can you remember the three lab methods for separating mixtures? filtering chromatography distillation Which of these does each method do? A separates a solvent from a solution B separates a solid from a liquid C separates substances with different solubilities 8F Separating mixtures

© OUP: To be used solely in purchaser’s school or college 8F Mixtures – composition of air Air is not a pure substance, it is a mixture of gases. What gases are present in air? Which gas do we need to inhale to stay alive? Is the composition of air always the same?

© OUP: To be used solely in purchaser’s school or college 8F Mixtures – composition of air But is inhaled air the same as exhaled air? What’s the formula for air? It’s a trick question – there isn’t a formula for air. Why not?

© OUP: To be used solely in purchaser’s school or college 1. Substances in a mixture are easier to separate than substances in a compound. 2.Pure water is a mixture. 3. Pure air is a mixture. 4.Substances in mixtures are not chemically joined. 5.Pure copper oxide is a mixture. 8F Mixtures – true or false? True or false? TRUE FALSE TRUE FALSE

© OUP: To be used solely in purchaser’s school or college Changing state 8F Compounds and mixtures

© OUP: To be used solely in purchaser’s school or college 8F Melting points and boiling points Reminder: If a substance is heated to its melting point it changes from a ?? to a ??. If a substance is cooled to its melting point it changes from a ?? to a ??. If a substance is heated to its boiling point it changes from a ?? to a ??. If a substance is cooled to its boiling point it changes from a ?? to a ??. Pure substances have fixed melting points and boiling points. Do mixtures have fixed melting points and boiling points?

© OUP: To be used solely in purchaser’s school or college 8F Mixtures Why do we put salt on roads and paths to melt ice? Because mixing salt with water: a)raises the freezing point to a higher temperature b)lowers the freezing point to a lower temperature c)raises the boiling point to a higher temperature?

© OUP: To be used solely in purchaser’s school or college 8F Mixtures Mixtures, like salt and water, do not have fixed melting points or boiling points. Increasing the amount of salt added to water: Increases the boiling point Decreases the freezing point Boiling potatoes: what is the effect of adding salt to the water?

© OUP: To be used solely in purchaser’s school or college 8F Element, compound, or mixture? How would you classify the following: element, compound, or mixture? air iron lemonade sugar soil Use the flow chart to help you. Element, compound or mixture? Are all the particles in this substance the same? Are all the atoms in these particles the same? It must be a mixture! A mixture is a collection of substances made of different particles that are not chemically joined It must be an element. An element is a substance that contains just one type of atom. It must be a compound. A compound contains different atoms that are chemically bonded yesno yesno