Question

chemistry: u1l5 mixture separation
pre - work part 1: mixture separation practice

1. match the following mixtures by the best separation technique to use: you can match a mixture to more than one separation technique if it applies.
2. a muddy puddle
3. a mixture of vinegar and water
4. a mixture of oil and water
5. a bowl of cereal and milk
6. a mixture of black ink and water
7. sugar dissolved in water

a. filtration
b. chromatography
c. decanting
d. distillation
e. evaporation

1. compare and contrast evaporation and distillation. when would each be used?
2. what is the advantage of using distillation over evaporation when separating a saltwater solution?
3. why is decanting not as precise as filtration for separating mixtures?

pre - work part 2: step - by - step mixture separation plan
directions: in this activity, you will apply your knowledge of separation techniques to break down a complex mixture into its individual components. use what you know about filtration, distillation, evaporation, decanting, chromatography, and layer separation to brainstorm and design a plan.
step - by - step separation plan
think about which separation technique you would use at each step and explain why. you are given a mixture that contains the following components:

• sand (insoluble solid)
• salt (dissolved in water)
• water
• oil (floats on water)
• black ink (mixed into the water)

Explanation:

Step1: Match mixtures with separation techniques

1. A muddy puddle: The solid mud particles can be separated from water by filtration (A) as the mud is insoluble in water. Also, decanting (C) can be used initially to separate some of the clear - water on top from the settled mud at the bottom.
2. A mixture of vinegar and water: Distillation (D) is a good method as they have different boiling points.
3. A mixture of oil and water: Decanting (C) can be used as oil and water are immiscible and oil floats on water.
4. A bowl of cereal and milk: Filtration (A) can be used to separate the solid cereal from the liquid milk.
5. A mixture of black ink and water: Chromatography (B) can be used to separate the different components of the ink dissolved in water.
6. Sugar dissolved in water: Evaporation (E) can be used to separate sugar from water as water will evaporate leaving sugar behind.

Step2: Compare evaporation and distillation

Evaporation is used when you want to separate a soluble solid from a liquid and don't care about collecting the liquid. For example, separating salt from seawater when you only want the salt. Distillation is used when you want to separate a liquid - liquid mixture (components with different boiling points) or a soluble solid - liquid mixture and also want to collect the liquid. For example, separating alcohol from water or getting pure water from a salt - water solution.

Step3: Advantage of distillation over evaporation for salt - water solution

Distillation allows for the collection of pure water as a distillate while evaporation only leaves behind the salt and the water is lost to the atmosphere. So, if you want to obtain both the salt and the water in pure forms, distillation is better.

Step4: Decanting vs Filtration precision

Decanting is not as precise as filtration because in decanting, it is difficult to completely separate the liquid from the solid without some of the solid particles being carried over with the liquid, especially if the solid particles are fine or if the separation interface is not clear - cut. Filtration uses a filter medium that retains the solid particles more effectively, giving a more complete separation.

Step5: Separation plan for complex mixture

1. First, use decanting to separate the oil from the rest of the mixture as oil floats on water. Reason: Oil and water are immiscible and oil has a lower density.
2. Then, use filtration to separate the sand from the remaining mixture (water with salt, ink). Reason: Sand is an insoluble solid and can be retained by a filter.
3. Next, use chromatography to separate the different components of the black ink from the water. Reason: Chromatography can separate dissolved substances based on their different affinities for the stationary and mobile phases.
4. Finally, use distillation to separate the salt from the water. Reason: Water and salt have different boiling points, and distillation can separate them and collect the water as well.

Answer:

1. 1. A, C; 2. D; 3. C; 4. A; 5. B; 6. E
2. Evaporation is for getting solid from liquid when liquid is disposable. Distillation is for separating mixtures with different boiling - points and collecting both components.
3. Distillation can collect both salt and water in pure forms while evaporation only leaves salt.
4. Decanting may carry over solid particles, filtration is more effective at retaining solids.
5. Decant to remove oil, filter to remove sand, chromatograph to separate ink, distill to separate salt and water.