Fractional Crystallization of Salt and Sand

Separating a mixture using solubility differences

Crystallization Beginner (Middle School) 35 min ~$3.00

Objective

Separate a mixture of salt and sand using fractional crystallization, demonstrating dissolution, filtration, and evaporative crystallization.

Background

This classic separation technique exploits the fact that salt dissolves in water while sand does not. The mixture is dissolved in hot water, filtered to remove sand, and then the salt is recovered by evaporation. This is fundamentally how salt has been harvested from seawater for millennia.

Safety Warnings

  • Handle hot evaporating dish with tongs
  • Do not heat to dryness too rapidly — spattering risk

Required PPE

goggles

Materials

  • Salt-sand mixture (10 g)
    Pre-mixed approximately 50:50
  • Distilled water (100 mL)

Equipment

250 mL beaker Filter paper Funnel Evaporating dish Hot plate Stirring rod Analytical balance

Procedure

1

Weigh 10 g of the salt-sand mixture and record the mass.

2 min
2

Add the mixture to 100 mL of warm water in the beaker. Stir for 5 minutes to dissolve all the salt.

5 min
3

Filter the mixture through filter paper. The sand remains on the filter; the salt solution passes through.

5 min
4

Rinse the sand on the filter with a small amount of distilled water. Dry the sand and weigh it.

5 min
5

Pour the filtrate into the evaporating dish. Heat gently on the hot plate to evaporate the water.

12 min Remove from heat before completely dry
6

Once dry, weigh the recovered salt. Calculate the percentage of each component.

3 min
7

Compare the total recovered mass with the initial mass. Calculate percent recovery.

3 min

Expected Results

The total mass of recovered salt + sand should be close to the original 10 g (typically 90-98% recovery). Some loss occurs during transfer and on filter paper. The separated components should be visually distinct.

Cleanup

Salt solution can go down the drain. Sand can go in the trash. Rinse all glassware.

Details

Category
Crystallization
Difficulty
Beginner (Middle School)
Duration
35 min
Est. Cost
$3.00
Steps
7
Materials
2

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Frequently Asked Questions

What is the objective of Fractional Crystallization of Salt and Sand?
Separate a mixture of salt and sand using fractional crystallization, demonstrating dissolution, filtration, and evaporative crystallization.
How difficult is Fractional Crystallization of Salt and Sand?
This experiment is rated as Beginner (Middle School). It takes approximately 35 minutes to complete.
What safety precautions are needed for Fractional Crystallization of Salt and Sand?
Key safety precautions include: Handle hot evaporating dish with tongs; Do not heat to dryness too rapidly — spattering risk.
What materials are needed for Fractional Crystallization of Salt and Sand?
The main materials required are: Salt-sand mixture, Distilled water.
What results should I expect from Fractional Crystallization of Salt and Sand?
The total mass of recovered salt + sand should be close to the original 10 g (typically 90-98% recovery). Some loss occurs during transfer and on filter paper. The separated components should be visually distinct.