filtrration and crystalisation (atomic structure and periodic table )

Question 1

what is a physical separation technique

Answer 1

physical separation techniques are used to separate mixtures. They can’t be used to separate the elements in a compound

Question 2

describe what filtration is

Answer 2

filtration is used to separate an insoluble soli from a liquid (insoluble means can’t dissolve in water)

Question 3

give an example where filtration would be used

Answer 3

silver chloride + water

silver chloride is insoluble in water so we have a solid material suspended in a liquid

Question 4

how would you filter out silver chloride from a liquid

Answer 4

As the silver chloride is insoluble in water, we can use filtration to separate these two substances. To do this we use:
1) Use a filter funnel and filter paper (place the filter paper inside the filter funnel)

2) Pour the mixture into the filter paper . The liquid which is water passes through the tiny pores in the paper. We can collect the water in a beaker.
3) The solid material, which is the silver chloride, can’t pass through the filter paper so it is trapped. Therefore, the liquid is separated from the solid

Question 5

what is crystallisation

Answer 5

crystallisation s used to separate a soluble solid from a liquid

Question 6

give an example where crystallisation would be used

Answer 6

sodium chloride (aq)+ water

sodium chloride is aqueous ( dissolved in water)

Question 7

how would you separate sodium chloride from water (crystallisation)

Answer 7

we want to separate the sodium chloride from the water.
If we leave it for a few days the water will evaporate. This will leave behind crystals of solid sodium chloride.

The symbol is now an “s” instead of “aq” as now the sodium chloride is a solid.
If we wanted to make the crystallisation happen faster we could gently heat the solutions to evaporate the water. We must be careful that heating will not effect the chemical we are trying to heat

Question 8

how can we use filtration and crystallisation to separate rock salts

Answer 8

1) Rock salt is simply a mixture of salt and sand (they spread it out on the roads during winter)
2) Salt and sand are both compounds - but salt dissolves in water and sand does not. This difference in their physical properties gives a great way to separate them

what we do is:

1) Grin the mixture to make sure the salt crystals are small , so they will dissolve easily
2) Put the mixture in water and stir. The salt will dissolve, but the sand won’t
3) Filter the mixture. The grains of sand won’t fit through the tiny holes in the filter paper, so they collect on the paper instead. The salt passes through the filter paper as it’s part of the solution
4) Evaporate the water from the salt so it forms dry salt crystals