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2021-9-26 published at Science&Technology category

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1.UNIT 3: Pure substances and mixtures 1º ESO Susana Morales Bernal
2.To know that a substance is identified according to its characteristic properties like: density and melting or boiling points. To know the concepts of pure substance, heterogenous mixtures and dissolutions at experimental and theoretical level. To know that in the dissolution, the dissolved substances are disintegrated at molecular level. To know the differences between dissolution, dissolvent and solute. To differentiate between simple substance and compound. To know how to differentiate between dissolutions and heterogenous mixtures observing its properties. To know that the properties of the substances at macrocospic level cannot be applied to their molecules. To know how to draw molecular diagrams that they represent mixtures and pure substances. To distinguish between the most suitable methods to separate components of homogenous mixtures and those of heterogenous mixtures. To know how to use techniques of separation like the decantation, the filtration, the distillation, the crystallization or the heating to dryness to separate substances of a mixture. To know the parts of a distillation, crystallisation and heating equipment. To know the parts of a decantation and filtration equipment. To know the composition alloys of common use. To know the main substances that compose the air, as well as the proportion of nitrogen and oxygen. To know the physical properties most important of water. To know the approximated composition of sea water. Objectives Susana Morales Bernal
3.Characteristic properties A characteristic property is a physical or chemical property that we can use to identify a substance. Characteristic properties The temperature at which a substance changes from a solid to a liquid The temperature at which a substance changes from a liquid to a gas Mass and volume are not characteristic properties. A small piece of gold has less mass and less volume than a large piece of gold. They depend on the amount of substance. Boiling point Melting point Density The density is the relationship between the mass of an object and its volume Susana Morales Bernal
4.Classification of matter We can classify matter, in two categories: pure substances and mixtures Pure substance: only one substance, its characteristic properties do not change, in the same conditions of temperature and pressure The following systems are pure substances rock salt sugar mercury copper sulphate sulphur pyrite gold Susana Morales Bernal
5.Types of pure substances There are two types of pure substances: simple substances and compounds We can differentiate them, watching their behavior when exposed to heat or electricity. Compounds are those substances that decompose into simpler pure substances by means of heating or electrolysis. Simple substances are those which do not decompose into simpler pure substances by means of heating or electrolysis. Thus water is a compound because it is decomposed by electricity into two elements, hydrogen and oxygen. Rock salt, pyrite, sugar and copper sulphate are compounds too. Thus oxygen is a simple substance because it does not decompose by means of heating or electrolysis. Gold, mercury and sulphur are simple substances too. Susana Morales Bernal
6.Simple substances have equal molecules with only one type of atoms Compounds have equal molecules with two or more types of atoms Gas monoatomic Liquid monoatomic Gas diatomic Liquid diatomic Solid monoatomic From the point of view of their structure, the pure substances have only one type of molecules. Solid diatomic Solid diatomic Liquid diatomic Gas diatomic Structure of pure substances Susana Morales Bernal
7.Although only 92 elements occur naturally on earth, they can combine to produce an unlimited number of compounds. ELEMENTS Element is the representation of each type of atom, it is not the same as simple substance. An element has not properties, a simple substance has them. Susana Morales Bernal
8.Mixture: two or more substances, its characteristic properties change, depending on the type of substances is formed by and on the amount of each substance copper sulphate and water The following systems are mixtures dissolutions granite oil and water copper sulphate and water plumb iodide and water Susana Morales Bernal
9.Homogeneous: mixtures which have the same properties throughout the mixture. We can call this type of mixture, dissolution. For example: Sugar dissolved in water Salt dissolved in water Copper sulphate dissolved in water Some type of metal alloy like the cromium-molybdenum used in many bike frames Heterogeneous: mixtures which have different properties throughout the mixture. For example: Sand mixed with water Oil mixed with water Granite Plumb iodide and water There are two types of mixtures: homogeneous and heterogeneous. Types of mixtures Susana Morales Bernal
10.From the point of view of their structure, the mixtures have two or more types of molecules. Homogeneous mixture: it has different molecules distributed uniformly Heterogeneous mixture: it has different molecules that are not distributed uniformly Solid dissolution Liquid dissolution Gaseous dissolution Heterogeneous mixture of one solid and one gas Heterogeneous mixture of two liquids Heterogeneous mixture of one solid and one liquid Structure of mixtures Susana Morales Bernal
11.Homogeneous mixtures Homogeneous mixture: is that has the same properties at all its points A dissolution (solution) is a homogeneous mixture composed of two or more substances. Solute is the substance that is in smaller proportion, unless it is water in which case we consider it the dissolvent. When we mix two substances and we do not obtain a solution, we say that these substances are insoluble. When we mix two substances and we obtain a solution, we say that these substances are soluble. A solute is dissolved in another substance, known as a solvent. Susana Morales Bernal
12.Process of solution When a dissolution of a solid in a liquid takes place, the molecules of the liquid bang to the solid, pulling molecules away and separating them. Finally, the molecules of the solid remain surrounded by molecules of the liquid and distributed uniformly. Before dissolving After dissolving Susana Morales Bernal
13.Methods of separation of substances in mixtures The main techniques of separation of the substances that integrate the heterogeneous mixtures are: decantation, filtration and magnetic separation The main techniques of separation of the substances that integrate the homogeneous mixtures are: heating to dryness, crystallisation and distillation Susana Morales Bernal
14.After this, we open the funnel tap and the liquid at the bottom of the funnel is transferred into a container. We do not collect the part of liquid that can contain a small part of the other liquid. After this, we collect the next layer in another container, obtaining two separate liquids. DECANTATION We use this methode to separate two or more inmiscible liquids with different densities. We put the mixture into a separating funnel and we allow it to stand for some time. This separates the liquids into layers. The liquid with the lowest density floats on the top and the one with higher density lies below it. Susana Morales Bernal
15.Then, we pour the mixture slowly into a container; through the funnel. We can see the particles of solid on the filter paper. We call residue to the solid particles and we call filtrate to the clear liquid obtained. FILTRATION We use this method to separate an insoluble solid from a liquid. We take a filter paper and fix it to a funnel. Susana Morales Bernal
16.MAGNETIC SEPARATION We use this methode to separate magnetic solids from non magnetic solids. Magnet Sulfur and iron filings Clock glass Iron filings are very small pieces of iron that look like a light powder. Susana Morales Bernal
17.HEATING TO DRYNESS We use this method to separate soluble solids from solutions. We heat the solution in an evaporating dish until the solvent vaporizes. When we heat: We waste energy Crystals are smaller The process is faster In this process we only obtain the solute, not the solvent. Susana Morales Bernal
18.CRYSTALLISATION We use this method to separate soluble solids from solutions. In this process we must wait for the liquid to evaporate at room temperature without heating it and the solid crystallizes. In the crystallisation: We do not waste energy Crystals are greater The process is slower In this process we only obtain the solute, not the solvent. Susana Morales Bernal
19.We use this method to obtain both the solute and the solvent from a solution. The solute can be a soluble solid or a liquid. We take the solution in a distillation flask and we heat it so that the solvent slowly starts to vaporize. We connect the distillation flask to a condenser tube which has a lower tube for the inlet of cool water and an upper tube for the outlet of water. The circulation of cold water in the condenser helps to cool the gases from the solution and they form the distillate. DISTILLATION We collect the distillate (the solvent) in a separate container. The remaining residue, in the distillation flask, is the solute. In this process we obtain the solute and the solvent. Susana Morales Bernal
20.To heat To crystallize Distillation Decantation Filtration Its characteristic properties change, depending on the type of subtances is formed by and on the amount of each substance can be MATTER Pure substance Mixture Homogeneous Heterogeneous is classified in They originate by means of physical procedures Has the same properties at all its points Has not the same properties at all its points can be Simple substances Compounds They originate by means of chemical procedures Equal molecules with only one type of atoms Equal molecules with two or more type of atoms Its characteristic properties do not change, in the same conditions of temperature and pressure These processes give rise Susana Morales Bernal
21.EXERCISE 1 Indicate which of the following properties are characteristic and which are extensive or intensive. Susana Morales Bernal
22.EXERCISE 2 Connect the terms of the two columns Granite Water Gold Salt with water Mercury Pure substance Heterogeneous rock Solution Liquid metal to room temperature Solid metal to room temperature Susana Morales Bernal
23.EXERCISE 3 Is the water that we drink an absolutely pure substance? No, because it is a heterogenous substance It is not pure, it has mineral salts dissolved Otherwise, we cannot drink it Of course, it is distilled water Susana Morales Bernal
24.EXERCISE 4 What do you remember? Separating components of a homogeneous mixtures. Join with arrows. By distillation By crystallisation By heating Salt and sea water in the salt mines Alcohol and water Copper sulphate and water Susana Morales Bernal
25.What do you remember? Separating components of a heterogeneous mixtures. By magnetism By filtration By decanting Sand and water Oil and water Sand and iron particles EXERCISE 5 Join with arrows. Susana Morales Bernal
26.EXERCISE 6 Can we decompose a pure substance in others by means of physical procedures? No, we cannot Yes, filtering it Yes, by means of distillation Clear that yes Susana Morales Bernal
27.EXERCISE 7 ……………………. is good for separating a liquid from a solution. ......................... is good for separating a soluble solid from a liquid. ......................... is good for separating an insoluble solid from a liquid. ......................... is good for separating two inmiscible liquids. Separating mixtures Complete the sentences. Use the words in the box. FILTRATION , HEATING, DECANTATION, DISTILLATION Susana Morales Bernal
28.EXERCISE 8 Each verb in the table represents a separation process. Write down the corresponding noun. Susana Morales Bernal
29.EXERCISE 9 A pure substance and heterogeneous A homogeneous rock A pure substance A heterogeneous solid mixture What is the rock called “granite”? Susana Morales Bernal
30.EXERCISE 10 Classify the following products as: simple substance, compound, dissolution or mix heterogeneous Susana Morales Bernal
31.EXERCISE 11 Thermometer, Cold water out, Vapour, Distillate, Solution, Heat, Cold water in, Condenser Distillation is the separation of a liquid from a solution by boiling and condensing. Use words from the box to label the diagram: Susana Morales Bernal
32.EXERCISE 12 Salt solution, Filter funnel, Filter paper, Sand, Conical flask, Mixture of sand and water, Beaker, Evaporating dish, Gauze, Tripod, Bunsen burner, Water We can heat to separate soluble solids from solutions and we filter to separate insoluble solids from liquids. Use words from the box to label the diagram: Susana Morales Bernal
33.EXERCISE 13 How can you separate oil from water? How can you separate a mixture of alcohol and water? How can you obtain salt from sea water? How can you separate a mixture of sand and stones? How can you separate a mixture of sulfur and iron filings? With a magnet With a separating funnel With a sieve Heating until water vaporizes Distilling Connect the terms of the two columns Susana Morales Bernal
34.EXERCISE 14 Classify the following systems as: simple substance, compound substance, homogeneous mixtures or heterogeneous mixtures SYSTEM A SYSTEM B SYSTEM C SYSTEM D Susana Morales Bernal
35.EXERCISE 15 Choose the correct letters in the boxes on the right. A B C D E F G H Susana Morales Bernal
36.EXERCISE 16 Classify the following diagrams as: simple substance, compound, mixture of simple substances, mixture of compounds, mixture of simple substances and compounds. Susana Morales Bernal
37.EXERCISE 17 Which of the following diagrams represent: The compound CO (gas) The simple substance O3 (gas) The compound H2O (liquid) The compound NaCl (solid) Susana Morales Bernal
38.EXERCISE 18 Is the air a pure substance? No, the air is a gas mixture. Yes, because it is a gas. No, because a simple gas form it. Yes, for that reason we can breathe it. Susana Morales Bernal
39.EXERCISE 19 We add a small amount of a solid substance to a glass with water. After a while, the solid substance disappears and the water is of pink colour. What is this process called? What tests can you do to verify it? Indicate which is the solute and which is the solvent. Make a drawing of how you imagine the molecules of the solid substance and water are, before and later. What changes occur in the molecules of the solid substance when it disappears in the water? Why does all the water change colour, although you do not shake with a teaspoon, and not only the part nearest where you put the solid? A classmate says that the water colours because the molecules of the solid are of pink colour and they mix with those of water that do not have colour. Do you agree? Justify your answer. A classmate says that if you want to return the water to its original transparent state, you can filter the mixture. Do you agree? Explain your answer. A classmate says that the pink solid is not the one that you think but another that has the same colour. How can you prove it? Susana Morales Bernal
40.EXERCISE 20 Revise your vocabulary. Choose a word and fill the blanks below compounds, simple, heterogeneous, atoms, pure substances , decantation, homogeneous, identify, mixtures, distillation, mixtures, physical, pure, crystallisation, change, depending, types, decompose, heating, electrolysis, filtration, dryness, substances, atoms, molecules, compounds, molecules A characteristic property is a ……………….. or chemical property that we can use to ……………….. a substance. We can classify matter, in two categories: ……………….. and ……………….. ……………….. substances are those which characteristic properties do not ……………….., in the same conditions of temperature and pressure. In the ……………….., the characteristic properties change, ……………….. on the type of subtances form it and on the amount of each substance. There are two ……………….. of pure substances: simple substances and ……………….. ……………….. substances are those which do not ……………….. into simpler pure substances by means of ………………. or ……………… . Simple .................... have equal ……………….. with only one type of ……………….. . ……………….. have equal ……………….. with two or more types of ……………….. . There are two types of mixtures: ………………. and ……………….. . The main techniques of separation of heterogeneous mixtures are: the ……………….., the ……………….. and the magnetic separation. The main techniques of separation of homogeneous mixtures are: the heating until ……………….., the ……………….. and the ……………….. . Susana Morales Bernal
41.GLOSSARY Alloy Atom Bunsen burner Clock glass Condenser Container Compound Crystallisation Decantation Dissolution Distillation Distillation flask Electrolysis Element Evaporating dish Filtration Frame Funnel Filter paper Heterogeneous mixture Homogeneous mixture Insoluble Layer Magnet Magnetic separation Mixture Pressure Pure substance Residue Separating funnel Simple substance Soluble Solute Solution Solvent Structure Susana Morales Bernal Test tube To bang To collect To decompose To dissolve To distribute To filter To float To give rise to To heat To identify To pull away To remain To shake To surround To transfer Tripod Wire gauze

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