Does Liquid Weigh More after Freezing and Boiling?

Grade Level: 5th - 6th; Type: Physical Science

Objective:

Students will discover whether boiling and freezing water will have an effect on how much it weighs.

Research Questions:

Ice is created when water is frozen past the freezing point which is 0ºC or 32ºF, under normal conditions. When water freezes, the particles are tightly packed together and are more stationary than in the liquid state. It is now a solid rather than a liquid. But does it weigh more? If you boil it, does water lose weight?

Materials:

• Water (ordinary tap water will work)
• Two cups that can hold boiling liquids
• Kettle ( to boil water)
• Freezer (to freeze water)
• Kitchen scale
• Pen and paper for notes

Experimental Procedure:

1. Weigh the cups you are going to pour the water in on the kitchen scale. Take a note of these numbers.
2. Fill both cups with equal amounts of water and weigh this on the kitchen scale. Keep note of this number.
3. Subtract the first number (the weight of the cup) from the second number (total weight) to find the weight of the water.
4. Take one cup and label it “boiling hot” and pour the water from this cup into a beaker (if you are using a lab burner) or in a pot if you are using a kitchen stove. Watch until it bubbles (you can also stick a thermometer in) and carefully pour all of the water back into the cup. Weigh this on the kitchen scale and keep note of this number.
5. Now take the other cup and label it “freeze.” Put this in the freezer for at least two hours or until it is completely frozen. Take it out and weigh it on the kitchen scale.
6. Evaluate your results: Did the weights change at all?

Suggested Chart

Terms/Concepts: Water; Ice; Molecular composition; Freezing temperature; Boiling temperature

References:

• http://www.cliffsnotes.com/study_guide/Freezing-and-Boiling-Points.topicArticleId-21729,articleId-21699.html
• http://library.thinkquest.org/20991/gather/formula/data/62.html
• A Drop of Water by Walter Wick (1997). Scholastic Press.
•  Braun, Charles L.; Sergei N. Smirnov (1993). "Why is water blue?"
• . J. Chem. Educ. 70 (8): 612. http://www.dartmouth.edu/~etrnsfer/water.htm
• Lide, D. R. (Ed.) (1990). CRC Handbook of Chemistry and Physics (70th Edn.). Boca Raton (FL):CRC Press.