How Cold Can You Go?
Students measure the ice water temperature as they test different amounts of salt added to bags of ice used to make ice cream.Copyright 2010 Ursula Koniges, AMPS Program, Polytechnic Institute of NYU
Students explore materials engineering by modifying the material properties of water. Specifically, they use salt to lower the freezing point of water and test it by making ice cream. Using either a simple thermometer or a mechatronic temperature sensor, students learn about the lower temperature limit at which liquid water can exist—such that even if placed in contact with a material much colder than 0 degrees Celsius, liquid water does not get colder than 0 °C. This provides students with an example of how materials can be modified (engineered) to change their equilibrium properties. They observe that when mixed with salt, liquid water's lower temperature limit can be dropped. Using salt-ice mixtures to cool the ice cream mixes to temperatures lower than 0 °C works better than ice alone.
Using instruments such as thermometers and mechatronic sensors to gather data is an important skill for engineers who conduct research as part of the engineering design process. Materials engineers experiment to modify material properties to yield certain desirable characteristics to meet client and product needs.
After this activity, students should be able to:
- Take measurements and organize data in a simple chart.
- Describe the material properties of water.
- Describe how material property modification can be used to make materials useful for specific tasks.