b. Compare dissolution times in room temperature and hot water. Using this a model, what can you deduce about he relationship between temperature and weathering rate?

Lesson 5.6

Does Temperature Affect Dissolving?

Adding energy (heating) increases molecular motion.

Increased molecular motion competes with the attraction between solute molecules and tends to make them come apart more easily.

Increased molecular motion causes more solvent molecules to contact solute molecules and pull on them with more force, usually resulting in more dissolving.

Since different substances are made from different atoms, ions, or molecules, increased temperature will affect their dissolving to different extents.

Summary

Students revisit the dissolving M&M activity from Lesson 4. They will design an experiment to see if temperature affects the amount of dissolving of the sugar coating of an M&M.

Students will be able to identify and control variables to design an experiment to see whether the temperature of a solvent affects the speed at which a solute dissolves. Students will be able to explain, on the molecular level, why increasing temperature increases the rate of dissolving.

Download the student activity sheet, and distribute one per student when specified in the activity. The activity sheet will serve as the “Evaluate” component of each 5-E lesson plan.

Be sure you and the students wear properly fitting goggles. Warn students not to eat the M&M’s.

Materials for Each Group

M&M's (3 same color)

3 clear plastic cups

1 sheet of white paper

Room-temperature water

Hot water (about 50 °C)

Cold water (about 5 °C)

4 graduated cylinders (50 mL)

Hot water (about 50 °C)

Cold water (about 5 °C)

Salt

Sugar

Tablespoon

2 small cups

Explanation:

Hope it is helpful