You will need:
1. Place a funnel into the mouth of the balloon. Add at least 1 tablespoon of salt into the balloon.
2. Carefully measure 75mL of water into balloon, tie the balloon and shake to dissolve the salt.
3. Add 75mL of water to the other balloon and tie it.
4. Place both balloons within the freezer and start the timer. Check the balloons on hourly intervals.