Does it Dissolve?

Objectives

• Observe and understand the process of dissolving.

• Compare the differences between a solution and a mixture.

Materials

• Per Student:
  2 clear cups or other containers
  a sugar cube
  a rock (similar size as sugar cube)
  water
  spoon

Key Questions

• Pre-activity What will happen to the sugar when we add it to the water? What about the rock?
• Post-activity Where is the sugar now? Where is the rock now? Where did the sugar go? Can we get it back?

What To Do

1. Fill two clear cups or containers with warm water (which dissolves the sugar cubes faster than cold water).
2. Predict what will happen when you add the sugar cube and the rock to the water.
3. Add one sugar cube to one cup and a rock to the other cup.
4. Observe.
5. Taste the sugar water to see if you can detect the sugar (optional).

Extensions

• Experiment with other substances in your kitchen (e.g. drink crystals, hard candies, pepper, sand, flour, salt). What dissolves (makes a solution) and what does not (makes a mixture)?
• Compare how quickly a sugar cube dissolves when you stir it and when you let it sit still.
• Compare how quickly a sugar cube dissolves in cold water and in warm water.
• Dissolve and compare a white sugar cube and a brown sugar cube.
• Try pouring a small amount of sugar water into a shallow coloured dish. Allow the water to evaporate away (this might take a while). Can you find any sugar?
• Compare melting and dissolving. Melting is a change of state (from solid to liquid) while dissolving is a solid being integrated into a liquid.