Separating Mixtures Lab Answer Key

Guided investigation

1. Sand + Water. Which property lets you separate sand from water?

   Sand is an insoluble solid with particles large enough to be trapped by a filter.

2. Salt + Water. Why does filtration fail for salt water, and which method can recover the salt?

   Dissolved salt passes through filter paper. Evaporation removes the water and leaves salt crystals.

3. Iron Filings + Sand. How can one physical property separate iron filings from sand?

   Iron is magnetic and sand is not, so a magnet attracts the iron filings.

Data collection

Conclusion

Explain how physical properties help you choose a separation method.

1. Why can a mixture be separated by physical methods?

   Its substances are physically combined and keep properties that can be used to separate them.

2. Why does filter paper separate sand from water but not salt from water?

   Sand particles are insoluble and larger than the filter pores. Dissolved salt particles travel through with the water.

3. Which evidence should you use when choosing a separation method?

   Use a difference in physical properties such as particle size, solubility, magnetism, density, or boiling point.

4. Why might a mixture need more than one separation step?

   A mixture with three or more components may require a different property and method for each component.