Mixture Separation Techniques

When making coffee in a filter coffee machine, hot water passes through the ground coffee and the paper retains the coffee grounds, as shown in the figure.

What separation technique takes place inside the coffee maker?

After frying, water and oil remain in a saucepan forming two layers: the oil on top and the water at the bottom. If you let the saucepan stand and carefully remove the top layer, what separation technique are you using?

After cooking a broth, the fat is left floating, forming a yellowish layer on the surface. Cooks let the pot stand and then remove that layer with a ladle. What separation technique do they use? What property of fat makes it possible for it to work?

In a workshop, iron filings have been mixed with sand. When bringing a magnet close, the filings stick to it and the sand does not, as shown in the figure.

What separation technique is being used? Why does it work?

Grandmother has mixed chickpeas and lentils in the same drawer. Since chickpeas are larger, she uses a colander: the lentils pass through the holes and the chickpeas stay inside, as shown in the figure.

What is this technique called?

In the local bakery, they sieve the flour before kneading: the fine flour passes through the mesh of the sieve and the lumps stay on top. What technique is this? On what property of the particles is it based?

In a recycling plant, a conveyor belt carries iron scrap mixed with plastic and aluminum, and at the end of the belt there is a giant magnet. What material does the magnet separate from the rest? Why does aluminum not stick to the magnet?

In the laboratory, you want to recover the salt dissolved in a glass of salt water. You heat the solution: the water evaporates and the salt remains at the bottom, as shown in the figure.

What is this technique called?

Water and alcohol mix perfectly, but alcohol boils at a lower temperature than water. To separate them, the mixture is heated: the alcohol evaporates first, then that vapour is cooled and collected as a liquid in another container, as shown in the figure.

What technique is it?

Evaporation and distillation start in the same way: heating the mixture so that the liquid turns into vapour. How do they differ afterwards? Think about what is recovered in each case: the dissolved solid or the liquid?

A bottle contains a homogeneous mixture of water and alcohol.

1. a) Explain why neither filtration nor decanting works to separate them.
2. b) On what differing property of water and alcohol is distillation based to achieve this?

In salt pans, seawater is left in shallow pools exposed to the sun and wind for weeks, until a layer of salt appears at the bottom, as shown in the figure.

What separation technique takes place in salt pans? What is obtained and what has happened to the water?

Complete the sentence with the name of the appropriate technique: 'To separate an undissolved solid from a liquid, we use $\dots$; to separate two immiscible liquids, $\dots$; and to recover a dissolved solid by letting the liquid evaporate, $\dots$.'

Sand and salt have been mixed in the same jar. Put the steps in order to separate them and recover both:

1. a) Heat the water until it evaporates and salt remains.
2. b) Add water and stir so that the salt dissolves (the sand does not).
3. c) Pour the mixture over filter paper to retain the sand.

Three classmates have chosen the wrong technique. Find each person's mistake and correct it:

1. a) Aitana wants to separate water and oil by bringing a magnet close.
2. b) Mario filters salt water to keep the salt in the filter.
3. c) Sofía tries to separate sand and sugar by sieving, even though both grains are the same size.