i don't know the independent, constant and dependent variables of my experiment?

How does adding salt affect the freezing point of water?
1. Fill two identical containers(A and B) up with one cup of water each.
2. Make sure the temperatures of the two containers (A and B) are constant.
3. Measure the temperature of the water in each container (A and B) before the salt was added.
4. Add two tablespoons of salt to container A and stir the mixture.
5. Place both containers (A and B) into the freezer and record the temperature of each container every fifteen minutes for an hour.

Question

i don't know the independent, constant and dependent variables of my experiment?

How does adding salt affect the freezing point of water?
1.	Fill two identical containers(A and B) up with one cup of water each.
2.	Make sure the temperatures of the two containers (A and B) are constant. 
3.	Measure the temperature of the water in each container (A and B) before the salt was added. 
4.	 Add two tablespoons of salt to container A and stir the mixture. 
5.	Place both containers (A and B) into the freezer and record the temperature of each container every fifteen minutes for an hour.

anonymous · Answer

Independent variable is the thing that you have control over, so in this case, it would be the salt. The dependent is the thing that you can't control, which may be the temperature. The constant is something that remains the same throughout the experiment, so it would be the amount water.