Activity 6.7 in Class 7 Science is about observing the effect of temperature on the solubility of a solid substance. This activity helps students understand the concept of solubility and how temperature affects it.

Materials Required
- A beaker
- A glass rod
- Water
- Sugar

Procedure
1. Take a beaker and fill it with water.
2. Place the beaker on a heating source and heat it until the water starts to boil.
3. Add sugar to the boiling water and stir it with a glass rod until it dissolves completely.
4. Remove the beaker from the heating source and let it cool down.
5. Observe the solution carefully and note down your observations.

Observations
- The sugar dissolved completely in the boiling water.
- As the solution cooled down, the sugar started to crystallize and settle at the bottom of the beaker.

Explanation
Solubility is the ability of a substance to dissolve in a solvent. In this activity, we observed that sugar dissolved completely in boiling water but started to crystallize as the solution cooled down. This is because the solubility of a substance increases with an increase in temperature. When the water was heated, the molecules in the water gained energy and moved faster, creating more space for the sugar molecules to dissolve. However, as the solution cooled down, the molecules in the water slowed down and the space for the sugar molecules reduced, causing them to crystallize and settle at the bottom.

Conclusion
This activity helped us understand the concept of solubility and how temperature affects it. We learned that the solubility of a substance increases with an increase in temperature.

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