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Mixtures (EC 7)
| Question | Answer |
|---|---|
| Mixtures | A combination of two or more substances |
| Pure Substance | Contains only one type of particle |
| Homogeneous Mixture | A mixture in which the composition is uniform throughout the mixture. |
| Heterogeneous Mixture | A mixture in which the composition is not uniform throughout the mixture. |
| Solution | A mixture of one substance dissolved evenly throughout another. The mixture in which the particles of the components are so small that they're invisible, even under powerful microscopes |
| Light In A Solution | The particles don't reflect light, allowing it to pass straight through a solution without being scattered |
| Suspension | A mixture of two substances, in which a solid is mixed through (dispersed), undissolved, in a liquid. After a while, it will eventually settle to the bottom of the container as a sediment. |
| Shaking a Suspension | Often needs to be shaken or stirred before use to spread the sediment through the liquid, doing so will usually form a cloudy liquid |
| Colloid | A mixture in which the particles are small enough that they stay suspended even when the mixture is left to stand. The substances do not separate. |
| Origin Of A Colloid | Comes from the Greek word kola, which means 'glue'. You can think of it as a substance being 'stuck' suspended in another substance. |
| Benefit Of A Colloid | The benefit is that there is no need to mix them before using them. Hair gel and hand cream are examples. |
| Emulsions | A colloid of two or more liquids. Usually, one liquid is the 'base' and the other is broken into tiny droplets spread throughout the base. |
| Example Of A Emulsion | Milk is an example, with tiny droplets of fats and oils spread throughout the base, which is water. |
| Leaving An Emulsion | In some cases, when mixtures like this are left to settle, the tiny droplets float above the base liquid. This is different from what happens in a suspension, where the solid particles tend to fall to the bottom. |
| Emulsifier | A substance that is added to these mixtures to allow the liquids to remain completely mixed. |
| Soluble | A substance that can dissolve in a liquid |
| Insoluble | A substance that cannot dissolve in a liquid |
| Solute | The substance dissolving |
| Solvent | The liquid which the solute dissolves into |
| Concentration | How solutions are compared by how much solute is in the solvent. |
| Dilute | If just a little solute is dissolved (low concentration) |
| Concentrated | If a lot of a solute is dissolved (high concentration) |
| Saturated | If no more solute can dissolve into a solution |
| Working With Solutions | We often work with solutions in our everyday lives. By adding solutes to pure liquids, the properties of the pure liquids may change. An example is adding bath crystals to a bath to give the water a pleasant smell. |
| Water As A Solvent | Water is a good solvent. This is one of its most important properties. Our digestive system uses water to dissolve our solid and liquid food, and to break up the food into nutrients that our body needs to build new cells, grow and repair. |
| Water As A Solvent In Our Body | Our bodies are more than 60 per cent water. Our blood, which is mainly water, transports oxygen to every cell and carries away dissolved carbon dioxide gas (a waste product). |
| Water Dissolving Gas | Without water’s ability to dissolve gases, there would be no underwater life in our oceans and lakes and no fish in the rivers. These creatures all live by extracting dissolved oxygen gas from the water. |
| What Might Be Dissolved | There are many other colourless and clear liquids, and you do not know what substances might be dissolved in them. Tasting may be dangerous |
| Magnetic Separation | Magnetic separation uses magnets to attract and separate objects. Magnetic substances are attracted to a magnet. |
| Example Of A Magnetic Separation | Some metals are magnets. Tin cans are magnetic, whereas aluminium cans are not. Sometimes large magnets are used to separate tin cans in the rubbish from aluminium cans. This means both types of cans can be recycled in different ways. |
| Decanting | The careful pouring of liquid, or decanting, is often done to remove the sediment. |
| Density In Decanting | The substances that sink are denser than the substance on the top. The particles in dense objects are packed together more tightly than those in less dense objects. |
| Density Of Oil And Water | Oil floats on top of water because the particles in the oil are packed very loosely. The water particles pack together more tightly, so they sink to the bottom below the oil. |
| Sedimentation | The act of letting the denser substance sink to the bottom as sediment so the less dense rises to the top and is easier to collect |
| Floatation | The opposite of sedimentation as it allows the less dense substance rise to the top for collection. This is done by putting a more dense substance in the mixture so the less dense object rises up for easier collection. |
| Sedimentation And Floatation In Sewage | Sewage is left in settling ponds to allow the sediment to settle to the bottom. Fats and oils that float to the top of the ponds can be scooped off for digestion by bacteria. |
| Sedimentation And Floatation In Oil Spills | Oil spills can be cleaned up using the fact that oil floats on the surface of water. Cork and other substances can be sprinkled on top of the oil to soak it up, and these substances are then scooped off and squeezed out. |
| Flocculants | Sometimes sedimentation is more difficult. Chemicals called flocculants can be added to a mixture to make the particles clump together. This makes them heavy enough to settle to the bottom. Flocculation is regularly used to separate substances from water |
| Aboriginal And Torres Strait Islander Peoples Separating Mixtures | Some mixtures can be separated by their ability to be blown away. Such as, a variety of local seeds collected before being beaten with sticks to remove the seeds. Blowing air gently under the mixture leaves the heavier seeds to be used for food. |
| Yandying | Its done by placing the mixture in a shallow wooden dish, called a Yandy which is gently shaken. The dense sand sinks to the bottom and the less dense dirt and larger seeds float on the surface. This process is very similar to gold panning. |
| Filtering | Filters have a series of holes in them that lets through small things but traps larger particles. Filtering separates solids from liquids (or solutions) as the particles of the solution or liquid are smaller than the size of the holes in the filter paper. |
| Sieving | Separates solids according to the size of their particles. When you use a sieve, if it is smaller than the hole passes through, and the larger solids are left behind in the sieve. Sieves can separate solids of different sizes. |
| Filter paper | Filter paper has holes that are too small to see. Solutions can flow through the filter paper because the particles in the solution are small enough to fit through the holes; however, most solid particles in suspensions are not. |
| Different Filter Papers | Different filter papers come with different sized holes. Coffee filters and the filters found in the vacuum cleaner bags are both made of paper filters. |
| HEPA | High-efficiency particle arrestance filters are used in vacuum cleaners, air conditioners and face masks to remove even tiny dust particles. |
| Gas Mask Filters | Sometimes filters remove substances using chemicals rather than by physically stopping them. Gas masks often contain a special type of charcoal that attracts and holds onto some poisonous gases. |
| Fast Spinning Equipment | Some playgrounds have equipment that spins around very fast. When you spin very fast on this equipment, you can feel a force pulling you towards the outside of the spin. Heavy objects feel the pull more than light objects. |
| Centrifuging | Separates light/heavy particles by spinning a mixture. A machine that spins very quickly. Small test tubes of mixture are inside inside of the bowl of the centrifuge. The spinning motion causes the heavier particles to move to the bottom of the tubes. |
| Centrifuging Blood | When blood is spun in a centrifuge, the heavier red blood cells, , sink to the bottom, leaving the yellowish liquid part of blood (plasma and platelets) at the top. Medical professionals use different parts of blood depending on the medical need. |
| Centrifuging Dairy Products | Centrifuges are used in dairy processing factories to separate cream from milk. Salad spinners and washing machines also use this principle. |
| Evaporation | When a liquid is boiled into a gas. Every substance evaporates at a different temperature. |
| Boiling Points | Different boiling points of liquids can be used to separate. A mixture of water and turpentine can be easily separated because the water will evaporate first. The water will become a gas (water vapour) and separate from the turpentine. |
| Crystallisation | Uses evaporation to separate mixtures. Salt evaporates at 1414°C. A mixture of salt and water is heated, the water evaporates first, leaving behind the salt. This process of evaporating the solvent and leaving behind the solute is called crystallisation. |
| Distillation | When we want to keep the substance with the lower boiling point. Distillation collects the gas that evaporates from a mixture and cooling it down so that it becomes a liquid again. This cooling down of a gas into a liquid is called condensation. |
| Condensation | When a gas is converted back to a liquid |
| Residue. | The substance caught in the filter paper after filtering |
| Filtrate | The substance that passes through the filter paper after filtering |
| Condensation | The cooling down of a gas to a liquid |
| Distillate | The liquid collected through the process of distillation |
| Solubility | Another property that can differ between substances. Describes how easily a substance dissolves in a solvent. |
| Solubility In Dyes | Some have a higher solubility than others. This can be used to separate them from one another. Many have small particles that are suspended in a solvent. They are usually made from plants or minerals. |
| Paper Chromatography | The end of the absorbent paper is dipped in water so the water slowly moves up the paper. As the water goes past the dye , the most soluble dye dissolves first and moves up and then the rest. Most soluble=Top Least soluble=Bottom. |
| Chromatography | Scientists use it to find out what substances are in a mixture. It works because different substances move through the equipment at different times. The height of each peak tells the scientists how much of a particular substance is in the mixture. |
| Complex Chromatography | More complex and sensitive chromatography instruments are used to separate mixtures such as drinks and polluted air. Science labs often have chromatography equipment that can be used to detect 1 g of a substance in thousands of litres of solution |
| Uses of Chromatography in Racing | One of the uses of chromatography today is to identify athletes who use banned substances when they complete by testing their urine. A chromatography machine separates all the substances in the urine, including any illegal drugs that leave the body. |
| Chromatography In Airport security | Airport security tests for illegal drugs. Chromatography paper is wiped over a person or their bag and then inserted into a machine. A gas is pushed through the paper. If the drug is soluble in the gas, it will dissolve and be detected by the sensors. |
| When more solute is added to a saturated solution: | The the solute falls down as settlement and the concentration stay s the same. This is because in a saturated solution is saturated meaning it cannot dissolve any more solute in it so it will just sink to the bottom and the concentration stays the same. |
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