Quick answer: To separate a mixture, choose a method that uses a physical difference between its parts. This grade 6 science lab on separating mixtures gives the aim, the equipment, the safety points, a step-by-step method, sample results and 7 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
Can you separate three solids that are all mixed together? In this lab you use a magnet, water, filter paper and heat to separate iron filings, sand and salt. You then weigh each part to find how much of the mixture you recovered.
Level: Grade 6 science (Year 7 · Class 6) · Curriculum: MS-PS1-2
Aim
To separate a mixture of iron filings, sand and salt into its three parts, and to find the percentage of each recovered.
Equipment
- 30.0 g mixture: 3.0 g iron filings, 15.0 g sand, 12.0 g salt
- Magnet in a plastic bag
- Two beakers, stirring rod, funnel, filter paper, conical flask
- Evaporating dish, tripod and hot plate
- Balance and water
Safety
Wear goggles. Iron filings and hot salt can get into eyes. The hot plate and dish stay hot for several minutes; use tongs and let them cool. Wash your hands afterwards.
Method
- Weigh the mixture. Run the magnet, in its bag, over it and shake the filings off into a dish. Weigh them.
- Put the remaining mixture in a beaker, add 100 mL of water and stir for 2 min.
- Fold the filter paper and pour the mixture through the funnel into the flask.
- Rinse the residue with a little water, dry it and weigh the sand.
- Heat the filtrate gently in the evaporating dish until crystals appear, then let it dry. Weigh the salt.
Results
Sample measurements from one group:
| Substance | Mass in mixture (g) | Mass recovered (g) |
|---|---|---|
| Iron filings | 3.0 | 2.9 |
| Sand | 15.0 | 14.8 |
| Salt | 12.0 | 11.2 |
| Total | 30.0 | 28.9 |
Analysis questions
Question 1 Total recovered
Show that the total mass recovered is 28.9 g and calculate the percentage recovered.Question 2 Percentage for each part
Calculate the percentage recovered for iron, sand and salt, to 1 decimal place.Question 3 Largest loss
Identify the substance with the lowest percentage recovered and suggest two reasons.Question 4 Why the magnet first?
Explain why the magnet is used before water is added.Question 5 Where is the salt?
State what the filtrate contains and why filtering did not collect the salt.Question 6 Missing mass
Calculate the mass lost overall and suggest where it went.Question 7 Improve the lab
Suggest one change that would increase the percentage recovered.
