Decanting, Sieving, and Filtration PDF

Decanting, Sieving, Filtration  Imagine a mixture of gravel (small stones) and water, how can you separate them in the most simple and quickest way? It is not picking out the gravel by hand. Decanting Decanting is a technique which can be used to separate a dense, insoluble solid su...

Decanting, Sieving, Filtration  Imagine a mixture of gravel (small stones) and water, how can you separate them in the most simple and quickest way? It is not picking out the gravel by hand. Decanting Decanting is a technique which can be used to separate a dense, insoluble solid substance from a liquid The solid sinks and forms a sediment at the bottom of the container. By carefully pouring the liquid into a new container the solid is left behind in the first container  Decanting is only a useful method if the solid particles readily settle to the bottom. It would not be useful, for example, in separating fine silt/mud particles from water, as they often remain suspended in the water.  Decanting is also used to when pouring some wines A wine stored horizontally in a cellar must be stored upright for a few days to allow the solids to sink and settle and form a sediment at the bottom of the bottle. The wine must then be carefully poured to keep the sediment behind in the bottle. Sand and gravel How could you separate a mixture of sand and gravel? You could physically pick out the gravel with tweezers but it would take a long time. Ideas? Sieving How does sieving work as a separation method?  A sieve can be used to separate a dry mixture of two solids where one has bigger particles. A sieve is chosen which has holes that are small enough to allow one of the particles through but not allow the other particle through  How could you use sieving to separate a mixture of hazelnuts, peppercorns and sugar?  You can use a colander like sieve to separate the pasta from the water it was boiled in. The key principle here is that the food is bigger than the holes and the water will pass through the holes. Notes- Physical separation techniques Briefly explain how to separate a mixture of gravel and water (name and describe the separation technique) sketch a simple picture to show the process. Briefly explain how to separate a mixture of sand and gravel (name and describe the separation technique) Solutions When something dissolves we say it is soluble. The liquid that dissolves the solid substance is called the solvent. The solid that dissolves is called the solute. The new name for the liquid mixture that has the dissolved solute in is a solution Filtration Filtration is a special form of sieving that separates very fine solid particles from liquid or gas mixtures. Filter paper (or a similar substance with very fine pores) is used as a sieve. Filtration Filtration is a method for separating an insoluble solid from a liquid. For example, sand does not dissolve in water – it is insoluble. When a mixture of sand and water is filtered: the sand stays behind in the filter paper (it becomes the residue) the water passes through the filter paper (it becomes the filtrate)  The liquid particles are small enough to pass through the filter paper as a filtrate. The solid particles are too large to pass through the filter paper and stay behind as a residue.  Suspensions A suspension is a mixture of very small pieces of solid which are mixed in a liquid but do not dissolve. If left still, the solid pieces will separate from the liquid and either fall to the bottom or rise to the top. Sand in water, and chalk in water are examples of suspensions. These solids will sink to the bottom and form a sediment. Suspensions may separate quickly or stay suspended for a long time, depending on what they contain. In a solution the particles have dissolved, they are very small and cannot be seen. In a suspension the particles have not dissolved and are mixed within the liquid. Insoluble particles that do not dissolve can either form a suspension or if they are dense they can sink and form a layer of sediment  Equipment You can hold the funnel in a clamp collect the filtrate in a beaker Often easier to use a conical flask to fold the funnel and collect the filtrate Sawdust and water  Key words for describing the green mix separation experiment In the green mix experiment, we started with a solid mixture. It was a green colour but when we looked more closely, we saw that it was made of blue and yellow particles. We added water which acted as a solvent We found that the blue particles were soluble, they were able to dissolve in the solvent The blue particles and the solvent formed a solution. The yellow particles were insoluble. Some formed a sediment on the bottom of the flask and some formed a suspension. To separate the two types of particles in the mixture, we filtered it. The filtrate was blue and the residue was yellow.  Filtration notes 1. Describe how a mixture of chalk and water in a beaker can be separated. Use the following key words Beaker, suspension, conical flask, filter paper, filter funnel, residue, filtrate, chalk, water, soluble, insoluble 2. Draw and label a diagram to show how a mixture of chalk and water in a beaker can be separated. Solutions notes When something dissolves we say it is s______. The liquid that dissolves the solid substance is called the s_______. The solid that dissolves is called the s______. The new name for the aqueous mixture that has the dissolved solute in is a s_______ Salt is s_______ (dissolves) in water to make a salt water s________. Salt is the s______ and water is the s_______ Extension 1. Think of more things that are soluble or insoluble in water – write two lists. 2. Can you think of any other examples of solvents? How do we remove nail polish? It doesn’t wash off with water? How do you remove waterproof mascara? Eva is decorating her house and accidentally gets paint on the worktop, water does not wash it off, find out what she could use.  Filtration notes Draw and label a diagram to show how a mixture of chalk and water in a beaker can be separated. Use the following key words Beaker, suspension, conical flask, filter paper, filter funnel, residue, filtrate, chalk, water, soluble, insoluble Solutions notes When something dissolves we say it is soluble. The liquid that dissolves the solid substance is called the solvent. The solid that dissolves is called the solute. The new name for the aqueous mixture that has the dissolved solute in is a solution Salt is soluble (dissolves) in water to make a salt water solution. Salt is the solute and water is the solvent