Salt in Boiling Water By John-Paul Evans

Purpose What does ice do to hot boiling salt water and why does it do it?

Hypothesis Ice in measuring cups causes salt water to cool slower than ice in measuring cups without salt. Ice in measuring cups causes salt water to cool slower than ice in measuring cups without salt.

Interesting Facts First, heat does not flow from hot to cold. Second, salt water freezes 30 to 40 degrees Third, hot water freezes faster than cold water. Fourth, boiling water and adding salt takes longer to boil. Fifth, adding salt to water raises its boiling point.

Experiment

Materials Pot of water Hot Plate Salt Several Ice Cubes Watch with Minute Hand Pencil and Paper Two Thermometers Two Glass Measuring Cups Tablespoon Graph Paper

Procedure Set pot of water on hot plate and turn on hot plate until water boils. Ask mom or dad to help with this step. Put two ice cubes in each measuring cup. Put a thermometer in each cup. Put two tablespoons of salt in one measuring cup. Once water comes to a steady boil pure one half a cup of water in each cup. Observe what happens to the boiling water. Take temperature reading from the thermometer every ten seconds. Have mom or dad help time the ten second intervals. Record temperature change each ten seconds in each cup. Plot a table of temperatures of each cup using one axes and time of the other.

Data TimeTemp of water w/o salt Temp of water with salt 10 seconds50 C51 C 20 seconds50 C 30 seconds49 C50 C 40 seconds48 C50 C 50 seconds48 C50 C 60 seconds50 C 70 seconds50 C49 C 80 seconds49 C 90 seconds48 C49 C 100 seconds49 C 110 seconds48 C47 C

Analysis of Data and Observations

The data seems to show water with salt cools more slowly than water without salt.

Analysis Boiling water stopped and start cooling immediately. Temperatures and times show water cooling at different rates in each cup. Salt water cooled slower in ice than water without salt in ice. Did the experiment test your hypothesis? Yes How do you know? Because the data tells me so.

Conclusion Was your hypothesis correct? Yes What would you change in the experiment and why? I would add more salt to see if I could slow cooling. What are some new questions you have?

New Questions to Research Can more salt slow water cooling? Can more salt slow water cooling? Can more ice change the cooling of salt water? Can more ice change the cooling of salt water?