What kind of change is a mixture, physical or chemical?

Question

A student conducting an investigation dissolves salt in water and then
adds the salt solution to a beaker containing sand. The student now
wants to separate the salt and the sand from the mixture.
Which steps should the student perform to separate the salt and the
sand from the mixture?

Answer 1

A mixture involves a physical change, as the substances retain their individual properties and can be physically separated.

To separate the salt and sand from the mixture, the student can follow these steps:

1. Dissolve the Salt: If the salt is already dissolved in water, the first step would be unnecessary. But if the salt is in solid form with the sand, the student could add water to dissolve the salt completely.

2. Filter the Mixture: The student should pour the mixture (sand and saltwater solution) through a filter paper placed in a funnel or a filtering device. The sand will remain on the filter paper, while the saltwater solution will pass through into a separate container.

3. Evaporate the Water: To obtain the salt from the saltwater solution, the student can heat the solution gently (e.g., using a heater or hot plate) to evaporate the water. As the water evaporates, salt crystals will be left behind.

4. Collect the Sand: The sand collected on the filter paper can be removed and placed in a separate container.

By the end of these steps, the student will have separated the salt (now in solid form) and the sand, thus completing the physical separation of the mixture.