Question

a teacher mixes salt and gravel in a bowl of water and stirs the mixture. the teacher filters the mixture to separate out the gravel and then places the bowl of water containing salt on a hot plate. the water evaporates, and only the salt remains in the bowl.
which model best represents what occurred during the demonstration?
○ gravel △ water ○ salt ╬ new substance

Explanation:

The demonstration involves physical separations: first filtering to remove gravel (a large insoluble component), then evaporating water (a physical change, no new substance forms, only water is removed leaving salt). The given model incorrectly shows a new substance forming, which does not match the physical processes described. A correct model would first remove the gravel symbols, then remove the water symbols, leaving only the salt symbols with no new substances created.

Answer:

The provided model is incorrect. A correct model would:

1. First show the removal of all gravel (diamond symbols) from the mixture of salt, water, and gravel.
2. Then show the removal of all water (triangle symbols), leaving only salt (circle symbols) with no new substances produced.