Particles Summary Sheet

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Leslie Knight
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1 Particles Summary Sheet Mixtures A mixture is made from different substances that are not chemically joined. For example powdered iron and powdered sulphur mixed together makes a mixture of iron and sulphur. They can be separated from each other without a chemical reaction, in the way that different coloured sweets can be picked out from a mixed packet and put into separate piles. Separating mixtures The different substances in mixtures are usually easily separated from one another. The method you use depends upon the type of mixture you have. Chromatography This is good for separating dissolved substances that have different colours, such as inks and plant dyes. It works because some of the coloured substances dissolve in the liquid better than others, so they travel further up the paper. Filtration Filtration is good for separating an insoluble solid from a liquid. (An insoluble substance is one that does not dissolve). Sand, for example, can be separated from a mixture of sand and water using filtration. That's because sand does not dissolve in water. Evaporation This is good for separating a soluble solid from a liquid (a soluble substance does dissolve, to form a solution). For example copper sulphate crystals can be separated from copper sulphate solution using evaporation. Remember that it is the water that evaporates away, not the solution. Simple distillation This is good for separating a liquid from a solution. For example, water can be separated from salty water by simple distillation. This method works because the water evaporates from the solution, but is then cooled and condensed into a separate container. The salt does not evaporate and so it stays behind.

2 7 Particles Summary Sheet The three states of matter A theory is used to explain observations (data). Scientists also use theories to make predictions, Expansion and contraction and test the predictions to find out if they are correct. If the predictions are not correct, then the theory may have to be changed to explain the new evidence. Substances expand or get bigger when they are heated up. They contract or get smaller when they are cooled The different down. This properties property can of solids, be useful. liquids and gases can be explained by the particle theory (or particle model). Solids, liquids and gases (the three states of matter) need to be handled and Thermometers stored differently work because of the these liquid different inside them properties. expands and For instance, rises up the solid tube materials when it can gets be hotter. taken to Metal a landfill parts site. can be fitted together without welding using shrink fitting. The animation shows how this 7 works. SOLID Materials expanding and contracting can also cause problems. Solids are For made example, up of bridges particles expand that are in the very summer close heat and need special joints to stop them bending out together of shape. and are held tightly together by strong What do the particles do bonds. Solids cannot be squashed, do not flow, have When substances expand or contract, their particles a stay fixed the shape same and size. volume, It is the and space are dense between (are heavy the particles that changes: for their size). (Volume is the amount of space something takes up. It is measured in units such as The particles in a solid vibrate cubic more centimetres when it is (cm heated, 3 ).) and take up more room. The particles in a liquid move around each other more when it is heated, and take LIQUID up more room. The particles in a gas move Liquids more quickly are made in all up directions of particles when that it are is heated, fairly and take up more room. close together; the bonds between the particles are weaker than the bonds in solids. This allows the particles to move past each other. Liquids cannot be squashed, flow quite easily and have a fixed volume but no fixed shape. Although they are dense, liquids are usually less dense AS than solids. ases are made up of particles that are well spread out, with no bonds between them. ases are quite easy to squash, flow easily, have no fixed volume and no fixed shape. The particles in a solid vibrate more and take up more room when the solid is heated ases are not dense.

3 7 Particles Summary Sheet The three states of matter A theory is used to explain observations (data). Scientists also use theories to make predictions, and test the predictions to find out if they are correct. If the predictions are not correct, then the theory may have to be changed to explain the new evidence. The different properties of solids, liquids and gases can be explained by the particle theory (or particle model). Solids, liquids and gases (the three states of matter) need to be handled and stored differently because of these different properties. For instance, solid materials can be taken to a landfill site. 7 SOLID Solids are made up of particles that are very close together and are held tightly together by strong bonds. Solids cannot be squashed, do not flow, have a fixed shape and volume, and are dense (are heavy for their size). (Volume is the amount of space something takes up. It is measured in units such as cubic centimetres (cm 3 ).) LIQUID Liquids are made up of particles that are fairly close together; the bonds between the particles are weaker than the bonds in solids. This allows the particles to move past each other. Liquids cannot be squashed, flow quite easily and have a fixed volume but no fixed shape. Although they are dense, liquids are usually less dense AS than solids. ases are made up of particles that are well spread out, with no bonds between them. ases are quite easy to squash, flow easily, have no fixed volume and no fixed shape. ases are not dense.

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5 7 Diffusion Particles Summary ( i d) The natural mixing of substances is called diffusion. Diffusion occurs because particles in a substance are always moving around. Diffusion is fastest in gases, and slower in liquids. Dilution When you add water to orange squash you dilute it. The colour becomes paler because the orange coloured squash particles are spread out more by the water particles. 7 Pressure in gases Pressure is caused by particles hitting the walls of the container they are in. The pressure may increase because: the container has been squashed, making the volume smaller; this means that the particles will be hitting the walls more often. the number of particles has been increased, which means there are more particles moving around to hit the walls. the temperature of the particles has increased, so they will move around faster and hit the walls harder and more often. If the particles are in a flexible container, like a balloon, an increase in pressure will make the volume increase. If the pressure becomes too great the balloon will burst. Air pressure is the pressure caused by air particles around us. Air pressure lets us suck things up using a straw and also causes a container to collapse if the air is sucked out. If all the air is sucked out of a container, you get a vacuum nothingness.

IGCSE (9-1) Edexcel - Chemistry

IGCSE (9-1) Edexcel - Chemistry Principles of Chemistry Element, Compounds and Mixtures NOTES 1.8: Understand how to classify a substance as an element, compound or mixture Classifications: S Class Element