UNIT 3 CLASSIFYING MATTER. Techniques to separate homogeneous mixtures: Techniques to separate heterogeneous mixtures:

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1 UNIT 3 CLASSIFYING MATTER 1. Classifying matter 2. Separation techniques Techniques to separate homogeneous mixtures: Crystallisation Distillation Chromatography Techniques to separate heterogeneous mixtures: Filtration Magnetic separation Liquid decanting 3. Solutions Concentration Classifying solutions 62

2 A pure substance is a material that can be represented by one formula. Eg : H 2 O, CO 2, Au The atoms that make the substance are bonded. (enlazados, we will study this concept in the next unit) There are two types of pure substances: Elements Compounds An element is a pure substance made of only one kind of atom. They can be isolated atoms: He, Au, Ag. 63

3 Or they can be in pairs, Cl 2, or threes, O 3, or more, but generally they are in pairs. A compound is a pure substance made of more than one kind of atom. H 2 O, CO 2, CO, HCl. A mixture is a material made up of two or more substances that can be easily separated by physical means. The substances are not bonded among them. A heterogeneous mixture is a material in which you can distinguish the components by a macroscopic approach. Hetero means different, it consists of visibly different substances. Examples: Pizza, fruit salad. A homogeneous mixture is a material in which you can t distinguish the components by a macroscopic approach. Language: The stress in the word components is like this components Homo means the same, it has the same uniform appearance and composition throughout. Commonly we call the homogeneous mixtures solutions. Homogeneous mixtures = solutions Examples: Coca-cola, tea. 64

4 APPARATUS and ACTIONS to to to 65

5 APPARATUS and ACTIONS WATCH GLASS VIDRIO DE RELOJ CONDENSER REFRIGERANTE ROUND- BOTTOMED FLASK MATRAZ DE FONDO REDONDO SEPARATORY FUNNEL /SEPARATION FUNNEL EMBUDO DE DECANTACIÓN FILTRATION FUNNEL EMBUDO DE VIDRIO FILTER PAPER PAPEL DE FILTRO TO HEAT CALENTAR TO POUR VERTER SPATULA ESPÁTULA TO STIR AGITAR STIRRING ROD VARILLA AGITADORA MAGNET IMÁN 66

6 SEPARATION TECHNIQUES There are different techniques to separate mixtures. Techniques to separate homogeneous mixtures: Crystallisation Distillation Chromatography Techniques to separate heterogeneous mixtures: Filtration or filtering Magnetic separation Liquid decanting or liquid decantation or liquid-liquid extraction You have to complete the next activity to learn the different techniques: Instructions: 1-Read the texts and underline the words you don t understand (don t ask the meaning of those words yet) It is used to separate two liquids that are not mutually soluble. (they don t mix together) Eg.: Water and oil The mixture is poured into a separation funnel; after a few minutes, the different components separate. This happens because these liquids don t mix and have different densities. The denser liquid goes to the bottom and the less dense goes to the top. The stopcock is opened to let the bottom liquid flow into a beaker and then is closed. The remaining liquid, the less dense, is collected in a different beaker. 67

7 It is used to separate a solid and a liquid which are not mutually soluble. Eg.: sand and water The mixture is passed through a filter paper in a filter funnel. The solid can t pass through the filter paper because its particles are bigger than the holes of the paper, but the liquid particles can pass through the paper. It is used to separate magnetic substances from non-magnetic substances. Eg.: Iron and sand A magnet is passed through the mixture and attracts the magnetic substance. It is used to separate a solid from a liquid. The solid and the liquid are mutually soluble. Eg.: salt and water The solution is heated and left to evaporate. As the liquid evaporates the solid falls to the bottom of the beaker and forms crystals. It is used to separate two liquids which are mutually soluble. Eg.: Alcohol and water. The solution is heated. The liquid with the lower boiling point evaporates first. The vapour passes through a condenser where it cools down and condenses into a liquid, this liquid is collected in the beaker. The liquids separate because they have different boiling points. 68

8 It is used to separate the colours of ink or pigments of plants. We put a sample of the solution on a filter chromatography paper, we put it in a solvent (water and alcohol for example), this solvent is called the eluent. The eluent rises and dissolves the sample. Due to the different solubility of the different components of the ink, they go up at different rates so we can separate them. 2-You are going to watch a video explaining a technique. While you are listening, write down the name of the technique and all the new words that you hear and then identify and label the text above that explains that technique. Repeat the same stages with all the techniques Technique Key words Video nº1 Video nº2 Video nº3 Video nº4 69

9 Video nº5 Video nº6 Language: NOUN INFINITIVE GERUND Decantation/Decanting To decant Decanting Filtration/ Filtering To filter Filtering Both crystallisation and crystallization are possible. Another example of this type of word is: colour or color. Language: Apparatus is uncountable, if you want to refer to an item you have to say a piece of apparatus. (Instrumental) Other synonyms are: lab instruments or devices. But both are countable. SOLUTIONS A solution is a homogeneous mixture that can be easily separated by physical means. 70

Language: In Chemistry the structure in a given amount of... is quite common.

10 It is composed of solute and solvent. Concentration of a solution The concentration of a solution is the amount of solute dissolved in a given amount of solution at a given temperature. Language: In Chemistry the structure in a given amount of... is quite common. (en una cantidad dada de ) Other similar expressions are: Given that Ex: Given that all the reactants are gases, we can measure the volume with one formula. (Dado que ) At a given Ex: We measure the solubility at a given temperature (A una dada.) We can classify solutions in two types: Dilute solutions, contain a low amount of solute. Concentrated solutions, contain a high amount of solute. 71

11 When we add the highest amount of solute that the solvent is able to dissolve, we have a saturated solution. Saturated solution is a solution that contains as much solute dissolved as possible. Language: ADJETIVE VERB Infitnitive VERB Past Dilute solution To dilute Diluted Saturated solution To saturate Saturated Concentrated solution To concentrate Concentrated We can also classify solutions as: Solute Solvent Example solid solid alloys (aleaciones) solid liquid Salt in water liquid solid amalgam (amalgama) liquid liquid milk gas liquid Oxygen in water gas gas air Ways to express the concentration of a solution: Concentration = 72

12 Concentration mass/volume in C m/v = g/l ; Kg/l ; g/ml... ACTIVITIES A1- Classifying matter. Draw using the kinetic theory and different colours: a)a mixture of water and salt. b)an element. c)a compound. d)a solution of three elements. e) An element (each particle has three atoms). f) A compound (each particle has three atoms). g)a solution of two compounds. 73

A2-Classifyng matter Complete the table as seen in the example: Picture Description This

One of them has two atoms and the other has one atom This is a heterogeneous mixture of

one atom This is a heterogeneous mixture of two compounds.

13 A2-Classifyng matter Complete the table as seen in the example: Picture Description This is a homogeneous mixture of two elements. One of them has two atoms and the other has one atom This is a heterogeneous mixture of an element of two atoms and, a solution of one compound of two atoms and an element of one atom This is a heterogeneous mixture of two compounds. One of them has two types of atoms and the other has three types of atoms. A3-Parroting. A4- Separation techniques Name the separation technique shown in each picture: 74

14 A5-Solutions. Calculate the concentration of a solution made by mixing 2g of salt and 10 ml of water 75

15 A6-Solutions. You dissolve enough sugar in 2 litres of water to obtain a 10 g/l solution. How much sugar have you dissolved? A7- Review (Writing and speaking activity) 76

16 A8-Review: Bingo activity Write 16 of the following words in the table below PURE SUBSTANCE ELEMENTS COMPOUNDS MIXTURE HETEROGENEOUS MIXTURES SOLUTIONS DECANTING FILTERING MAGNETIC SEPARATION CRYSTALLISATION DISTILLATION CHROMATOGRAPHY CONDENSER SEPARATION FUNNEL FILTRATION FUNNEL WATCH GLASS FILTER PAPER THERMOMETRE TO HEAT TO POUR SPATULA TO STIR STIRRING ROD MAGNET 77

17 1 EXERCISES 2 78

18 3 4 79

19 5 6 We prepare a solution of water and sugar. We add 2,5 grams of sugar to 50 ml of water. The solution has a volume of 51,5 ml. Calculate the solution concentration in g/l 80

20 7 How many grams of Br 2 are needed to make 250 ml of a 4.5 g/l solution? 8 The concentration of a solution of ClK is 24,5 g/l. Calculate the solute mass, in grams, that you will find in 750 ml of this solution

21 11 82

22 LABORATORY ACTIVITY Making solutions You are going to prepare 100 ml of a solution of sugar and water. We want a concentration of 50 g/l. 1. Write the formula for the concentration of mass/volume 2. Substitute the data in the formula 3. Work out the mass of sugar Before adding the sugar you have to weigh the sugar. To weigh the sugar you have to reset the watch glass. Now you have all the data that you need to prepare the solution. To prepare 100 ml you have to use a volumetric flask of that volume. First you have to introduce the solid. You can do it by dissolving the sugar in a volume of water smaller than 100 ml, (for example 50 ml). Then you introduce the solution to the flask. After that, you fill the flask up with water, to the line. The lower part of the water has to touch the line of the volume that you are measuring. You can do the final part with a dropper. Draw three pictures that explain how you did it: 83

23 Working with this solution. Let s calculate the density of the solution. Write the formula for the density: Choose a volume between 0 and 100 ml and write it: Measure this volume with the cylinder. Put a beaker on the scale and reset the scale. Then measure the mass of the solution that you have taken. M= Calculate the density using the formula: Questions: If we take 50 ml of this solution, how much sugar is contained in it? If we take 50 ml of the solution, how much mass will it have? What volume of solution will contain 3g of sugar? 84

24 alloy [ˈælɔɪ] GLOSSARY: amalgam [əˈmælgəm] bond [bɒnd] chromatography [ˌkrəʊməˈtɒgrəfɪ] crystallisation [krɪstələˈzeɪʃən] crystal [ˈkrɪstl] decant [dɪˈkænt] dilute [daɪˈluːt] distillation [ˌdɪstɪˈleɪʃən] element [ˈelɪmənt] formula [ˈfɔːmjʊlə] funnel [ˈfʌnl] heterogeneous [ˈhetərəʊ'd[zh]i:nI&s] homogeneous [ˌhɒməˈdʒiːnɪəs] mixture [ˈmɪkstʃə r ] pour [pɔːr] pure [pjʊə r ] soluble [ˈsɒljʊbl] spatula [ˈspætjʊlə] stir [st3ːr] substance [ˈsʌbstəns] technique [tekˈniːk] 85

2 nd exam of the 1 st term for 2 nd ESO G. 1. Look at the following picture:

2 nd exam of the 1 st term for 2 nd ESO G Name: 1. Look at the following picture: Date: What is the name of the separation technique that you see? What type of substances you separate with this technique?