Properties of matter_Mixtures.pptx.pdf

Physical and Chemical Changes https://www.javatpoint.com/physical-change-vs-chemical-change https://www.javatpoint.com/physical-change-vs-chemical-change 9 of 46 © Boardworks Ltd 2008 What is a MIXTURE? 10 of © Boardworks Ltd 2008 What is a mixture? A mixture contains two or more substances that are...

Physical and Chemical Changes https://www.javatpoint.com/physical-change-vs-chemical-change https://www.javatpoint.com/physical-change-vs-chemical-change 9 of 46 © Boardworks Ltd 2008 What is a MIXTURE? 10 of © Boardworks Ltd 2008 What is a mixture? A mixture contains two or more substances that are mixed together, but have not chemically bonded with each other. For example, seawater is a mixture of water, salt and other substances. A pure substance contains just one substance on its own. For example, table salt (sodium chloride) is a pure substance. For example, table salt (sodium chloride) is a pure substance. 11 of © Boardworks Ltd 2008 What are the properties of a mixture? The substances in a mixture are not chemically bonded together. It is usually quite easy to separate the substances The proportions in a mixture are not fixed The properties of a mixture are often an ‘average’ of the properties of the substances it is made from 12 of © Boardworks Ltd 2008 What is a SOLUTION? 13 of © Boardworks Ltd 2008 What is a solution? A solution is a special type of mixture that is made when one substance dissolves and mixes fully with another. For example, a cup of instant coffee is a solution. The solid that dissolves (e.g. coffee granules) is called the solute. The liquid that does the dissolving (e.g. hot water) is called the solvent. 14 of © Boardworks Ltd 2008 Solvents and solutes What is the solvent and what is the solute? substance solvent solute black tea water tea orange squash water flavours and sugar seawater water salt fizzy drinks water flavours/sugar/carbon dioxide wine water flavours and alcohol How many other examples of solutions can you think of? 15 of © Boardworks Ltd 2008 Special solutions Solutions do not have to be made from a solid and a liquid. Solutions can also be made by dissolving a gas into a solvent. For example, it is the dissolved oxygen in water that allows fish to breathe. Liquids can also be dissolved in other liquids, like alcohol in wine, and solids can even dissolve in other solids. For example, some alloys can be classified as solid solutions. 9 of 46 © Boardworks Ltd 2008 What happens when something dissolves? Calcium carbonate is not soluble in water because the calcium carbonate and water particles are not able to mix. Copper sulfate is soluble in water because the copper sulfate and water particles are able to interact and mix together. water water calcium carbonate 17 of 46 copper sulfate © Boardworks Ltd 2008 How does temperature affect solubility? Does sugar dissolve in cold tea? It does, but not as much as in a cup of hot tea. The sugar is more soluble at higher temperatures. The amount of a solute that can dissolve at a given temperature is called its solubility. How does temperature affect the solubility of a substance? The solubility of a substance usually increases as the temperature increases. 18 of 46 © Boardworks Ltd 2008 What is a PURE SUBSTANCE? 19 of 46 © Boardworks Ltd 2008 What is a PURE SUBSTANCE? A pure substance has no particles of any other substance mixed with it. In real life, very few substances are 100% pure. Tap water contains small amounts of different particles 20 of 46 © Boardworks Ltd 2008 Does purity matter? Purity matters if you are making a medical drug or a flavoring for the food It must not contain things that will harm people IMPURITY – an unwanted substance mixed with the substance you want 21 of 46 © Boardworks Ltd 2008 How can you tell if a substance is pure? A pure substance has a definite, sharp, melting point and boiling point. When solid contains impurity, its melting point falls When liquid contains impurity, its boiling point rises Example: 22 of 46 © Boardworks Ltd 2008 Solubility of gases Gases are unusual because their solubility decreases when the solvent gets hotter. Fish and other organisms that live in water survive by taking in oxygen that has dissolved in the water. Some scientists think that global warming is causing sea temperatures to rise. What effect do you think rising sea levels will have on the creatures that live in the sea? 23 of 46 © Boardworks Ltd 2008 24 of 46 © Boardworks Ltd 2008 How could you separate these mixtures? Suggest some methods by which you could separate out these mixtures: buttons and candies pebbles and sand pebbles and water sand and water salt and sand oil and water salt and iron. 25 of 46 © Boardworks Ltd 2008 Separating an insoluble solid How do you separate the mixture of sand and water? Separate the mixture by FILTERING The insoluble solid cannot pass through the filter paper but the water can. Residue – the solid that is trapped by the filter paper. Filtrate - The liquid that 26 of 46 passes through the filter paper© Boardworks Ltd 2008 Separating a soluble solid How could you separate salt from a seawater solution? Separate by EVAPORATION The solution is heated so that the water evaporates and leaves the dissolved solid behind. Separate by CRYSTALLISATION The solution is heated so that the crystals form It works because some soluble solids tend to be less soluble at lower temperature. 27 of 46 © Boardworks Ltd 2008 Separating Mixtures of Two Solids Use of Magnet This is used to separate magnetic substances such as iron from non magnetic ones Sublimation a method used to separate a substance that sublimes from one with a high melting point 28 of 46 © Boardworks Ltd 2008 Salty water Where does the salt around the Dead Sea come from? 29 of 46 © Boardworks Ltd 2008 Separating salt from seawater The Dead Sea is a salty lake, located between Jordan and Israel. The Dead Sea contains some of the saltiest water in the world! The Dead Sea is almost six times more salty than the ocean, so nothing is able to live in it and that’s why it is called ‘dead’. The heat of the Sun evaporates the water from the Dead Sea, and the salt that is left behind is collected in salt beds. 30 of 46 © Boardworks Ltd 2008 Separating salt from rock salt We also get salt from rocks called ‘rock salt’. Rock salt is a mixture of salt with sand and bits of rock. Rock salt was traditionally extracted by hand from underground mines; a very dangerous process. Today, rock salt is mined using earth-moving equipment before being purified. How could you use dissolving, filtering and evaporation to separate the salt from rock salt? 27 of 46 © Boardworks Ltd 2008 Simple Distillation This is the way to obtain a solvent from a solution Distillation has three steps: 1. evaporation 2. condensation 3. collection The solution is heated so that the liquid evaporates and is turned into a gas. Everything else is left behind. The gas cools in the condenser and turns back into a liquid, which can then be collected. 32 of 46 © Boardworks Ltd 2008 Separating miscible liquids Liquids that do mix together are described as miscible. An example of this is water and alcohol – these two liquids mix together easily. + How could you separate a mixture of miscible liquids? 33 of 46 © Boardworks Ltd 2008 Distillation This is used to separate a mixture of liquids from each other making use of their different boiling points It could be used to separate water and alcohol STEPS: 1. Heat the mixture in the flask. Mixture rises up in the column. 2. The vapours condense in the column, heating the beads in the column. 3. Ethanol no longer condenses only the water vapour. Water drips back to the flask When the thermometer 4. Ethanol vapour goes into the reaches 78oC, all ethanol has container. There it condenses. It gone, stop heating is collected in the beaker 34 of 46 © Boardworks Ltd 2008 Distillation This is used to separate a mixture of liquids from each other making use of their different boiling points It could be used to separate water and alcohol The solution is heated so that the liquid evaporates and is turned into a gas. Everything else is left behind. The gas cools in the condenser and turns back into a liquid, which can then be collected. 35 of 46 © Boardworks Ltd 2008 IMMISCIBLE LIQUIDS In laboratories, chemists use a separating funnel to separate immiscible layers. 36 of 46 © Boardworks Ltd 2008 Separating immiscible liquids Liquids that do not mix together are described as immiscible. On a small scale, immiscible liquids can be separated by simply removing the top layer using a pipette. oil + water 37 of 46 © Boardworks Ltd 2008 Chromatography Chromatography means colour-writing. Chromatography is used to separate mixtures of coloured or non-coloured substances that are soluble in the same solvent. A spot of the mixture is placed on some filter paper. In method A, the solvent is soaked up the paper. 38 of 46 In method B, the solvent is slowly dripped onto the paper. © Boardworks Ltd 2008 Identifying dyes in a mixture Dots of single dyes are placed alongside a dot of unknown mixture. The solvent washes up the paper, and then the pattern of the dyes in the mixture can be compared with the single dyes. Which dyes does the mixture contain? 39 of 46 © Boardworks Ltd 2008 Uses of chromatography How many uses of chromatography can you spot? 40 of 46 © Boardworks Ltd 2008