8F Compounds and mixtures

1. 8F Compounds and mixtures 8FCompounds and mixtures Element or compound Mixtures Changing state

2. 8F Compounds and mixtures Element or compound

3. 8F Element or compound – how are they different? Decide if these statements describe an element or a compound. 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

4. 8F Element or compound – how are they different? Check your answers. Elements contain only one type of atom cannot be broken down into anything smaller there are just over 100 different types hydrogen gas is an example Compounds contain more than one type of atom that are chemically joined can be broken down into their separate elements there are millions of different types sodium chloride is an example

5. 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 CuO One carbon to two oxygen CO2 One calcium to one carbon to three oxygen CaCO3 Hydrogen and oxygen in the ratio 2:1 H2O Carbon and hydrogen in the ratio 4:1 CH4 Potassium, nitrogen and oxygen in the ratio 1:1:3 KNO3

6. 8F Comparing properties Does a compound have the same properties as the elements it is made of?

7. 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?

8. 8F Signs of a chemical reaction How do you know when a chemical reaction is taking place? gives out a gas produces a solid colour changes glows cools down heats up produces smoke flashes

9. 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 acid carbonate copper + carbon oxide dioxide carbon + water + magnesiumdioxide chloride sodium + ironcarbonate chloride carbon + water iron + sodiumcarbonate chloride coppercarbonate iron + sodiumcarbonate chloride copper + carbon oxide dioxide sucrose carbon + water + magnesiumdioxide chloride carbon + water

10. 8F Element or compound? True or false? 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. TRUE TRUE FALSE FALSE TRUE

11. 8F Compounds and mixtures Mixtures

12. 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?

13. 8F 8F Separating mixtures filtering chromatography distillation Can you remember the three lab methods for separating mixtures? 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

14. 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?

15. 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?

16. 8F Mixtures – true or false? True or false? 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. TRUE FALSE TRUE TRUE FALSE

17. 8F Compounds and mixtures Changing state

18. 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?

19. 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?

20. 8F Mixtures Increases the boiling point Decreases the freezing point Mixtures, like salt and water, do not have fixed melting points or boiling points. Increasing the amount of salt added to water: Boiling potatoes: what is the effect of adding salt to the water?

21. 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? yes no 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 yes no 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