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Does it Dissolve?

In this activity, students observe and compare the features of a solution and a mixture.

What happens when we combine a liquid and a solid? When a solid dissolves, it seems to disappear. The dissolved solid is still there; we just can't see it.

Sugar is and example of a solid that breaks down into tiny pieces, and dissolves in water. When the sugar is spread completely throughout the water, we call this a solution.

Not everything dissolves, however. Rocks and sand do not dissolve in water—they sink to the bottom. We call this a mixture.

These activities are part of Science World’s Big Science For Little Hands program. They were developed and tested with preschool and kindergarten educators. Some of the activities are done in stations.

Mysterious Mixtures PDF from Big Science For Little Hands.

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.