Mixtures and Separating From Year 9 Chemistry SLO’s 6) Understand that substances are pure or mixtures. 9) Use the term mixture and illustrate with everyday examples. 10) Use the terms solute, solvent, solution, diluted, concentrated, soluble, insoluble. * insolubility/precipitation 11) Separate mixtures using decant, filter and evaporate and use these techniques. * chromatography, distillation, centrifuging

Pure Substances Because we cannot separate elements or compounds into any simpler substances easily we say call them PURE SUBSTANCES

If something is not a pure substance……. We call it a mixture Mixtures contain different substances MIXED together. These substances are not chemically joined and can be usually separated by physical means

For you to do Sort these items out into mixtures and pure substances: Air, polluted water, orange juice, helium gas, gold, sugar, concrete, milk, lipstick MixturesPure Substances Then do exercises 2-4 on p61

Separating mixtures GeneralExtension Decanting* Distilling Filtering* Centrifuging Evaporating

Mixtures in liquids When you stir sugar into a glass of water it seems to disappear. What actually happens to it? Is the sugar still there? Is it possible to get this sugar back?

Objective : -To make a solution of copper sulfate. -To understand and use the terms solute, solvent and solution.

Vocabulary word Predicted meaning After reading text book Clue words Solute Solvent Solution Literacy task

To make a solution of copper sulfate by carrying out a reaction between sulfuric acid and copper oxide, to filter and heat the products of the reaction.

1) Add 25mL of sulfuric acid (H 2 SO 4 ) to a small beaker. 2) Add a small spatula of copper oxide (CuO) and stir with a stirring rod. 3) Filter the solution 4) Pour filtered solution into an evaporating dish 5) Heat using a blue flame on tripod until 2/3 of the liquid has evaporated (leave to cool before touching!)

Word equation = Sulfuric acid + copper oxide → copper sulfate + water Balanced Chemical Equation = H 2 SO 4 + CuO → CuSO 4 + H 2 O We carried out the reaction above and evaporated the water off to leave behind solid copper sulfate (blue crystals)

1) Name the following for the practical you have just done A) Solute – B) Solvent – C) Solution – 2) On your terms and definitions sheet, identify the definitions for the words solute, solvent and solution – get your teacher to check once you have done this. Extension questions 3) What do you think you will see after the water had been evaporated and the solution is left to cool overnight? 4) Explain in terms of the particle theory what is happening to the water particles during evaporation 5) Draw scientific diagrams for the different stages of the practical you have carried out (filtering and evaporating)

Solutions pg 62 Solute = a substance that can dissolve (e.g. sugar) Solvent = a liquid that can dissolve a solute (e.g. water) Solution = the mixture that is formed when the solute dissolves in a solvent (e.g. the mixture of dissolved sugar and water)

Not everything will dissolve in a solvent Substances that can dissolve are called SOLUBLE Substances that do not dissolve are called INSOLUBLE A SUSPENSION is formed when an insoluble solute (e.g. sand) is placed in a solvent. The solute settles to the bottom.

Practical: soluble or insoluble? p63 Aim: to find out the solubility of some substances in water Method: Add a small spatula-full of each substance to two cm of water in a test tube and swirl to mix. If the substance doesn’t dissolve, heat gently with a bunsen Results: SubstanceObservationSoluble / slightly soluble / insoluble? Salt Sugar Coffee Flour Copper sulfate Tea leaves

Concentration pg 64 Solutions are concentrated or dilute Concentrated solutions have large amounts of solute in them Dilute solutions have small amounts of solute in them The colour of solutions may give you an idea of the concentration. Darker is often more concentrated.

Sometimes no more solute will dissolve in a solvent. Then the solutions is said to be saturated. This is like a kitchen sponge that won’t hold any more water - it is saturated!

Separating suspensions pg 67 Undissolved particles may be separated out. We use two methods to do this 1.Decanting – pour off the liquid and leave the solid behind

2. Filtering – pour the solution through a filter. The solid is left behind in the filter and is called the residue. The liquid is called the filtrate.

Extension 3. Centrifuge – we spin the solution and the heavy particles fall to the bottom and the lighter ones rise to the top.

Separating solutions It is possible to get back solute even once it is dissolved. We use two methods to do this: 1. Evaporation – heat the solution and evaporate off the water leaving the dissolved solid behind

2. Distillation – uses evaporation first and then you cool the liquid that is evaporating to collect it separately. EXTENSION

Chemistry Computer revision task Carry out the activities on eChalk Another good website to take a look at is Chem 4 Kids

Literacy task Arrange these terms in a diagram using links to show how they are related. TERMS matter,chemically bonded, mixture, physically separated, atom, compound, molecule, pure substance, metal, non-metal, element,

Separating mixtures Separating method Magnetism Chromatography Decanting Centrifuging Explanation Pouring off a liquid and leaving an insoluble solid behind. Uses high speed spinning to separate a suspended solid from a liquid. Used to separate iron metal from a mixture. Uses a solvent (eg- water) to separate a mixture of coloured substances.