Speeding Up and Slowing Down the Dissolving Process

Today we did another exploration where we were determining how to speed up or slow down the dissolving process. Yesterday, we determined that shaking and stirring the mixture helped it dissolve faster. Today we set up 3 cups; filled cup A with 100 ml of cold water, filled cup B with 100 ml of room temperature water, and cup C with 100 ml of hot water. Students then recorded the temperature of each cup and made predictions on how long they thought it would take for the salt to dissolve. They then put 1 teaspoon of salt into each cup and then stirred each mixture 5 times. They were then to wait and observe. As I walked around, students were amazed that the hot water mixture dissolved the quickest. They were even more amazed that the cold water mixture took longer to dissolve, but eventually it did. We made a connection to the hot water speeding up the dissolving process when we make jello (boil water and add to Jello mix.) We leaned today that heat speeds up the dissolving process.

Dissolving can be sped up in several ways. The normal ways are:
                          1. To crush the solid into a powder.
                          2. To stir the solid with the water.
                          3. To warm the water and the solid.

To slow down the dissolving process, you can leave it alone (not stir), do not break into smaller parts, and use cold water.