How Low Can You Go?

Overview

Objectives/Goals The objective is to analyze why salt is used to melt ice on roads and determine how salt lowers the freezing point of water and to prove the hypothesis: If water is mixed with salt, then it will freeze at a lower temperature than water without salt. Methods/Materials Three plastic cups were filled with 8 ounces of distilled water and different concentrations of sea salt. The control held only one cup of distilled water, while the other two cups had 1 or 2 tbsps of salt dissolved into them. All three cups were placed in the freezer and then the temperatures of each cup were measured by a food thermometer and recorded at timed intervals of 20 minutes until ice formed and the temperatures were stable. The data from three trials were averaged. Results The cup with 2 tbsp of salt froze at the lowest temperature with an average 14.7ºF, the water with 1 tbsp of salt froze at an average temperature of 22.5º, and fresh water froze at an average temperature of 30.6ºF. As shown by the data, the water with 2 tbsp of salt froze at the lowest temperature, the water with 1 tbsp of salt froze in the middle, and the fresh water froze at the highest temperature. Conclusions/Discussion According to the data collected, the hypothesis appears to be supported. The water did freeze at a lower temperature when salt was added to it in all three trials. The experiment supports the real life application of using salt to prevent and/or clear ice on roads, because salt lowers the freezing point of ice below the temperature of the surrounding area.

Competition history

• CSEF 2014 Chemistry · Entry J0627

Resources

• CSEF project summary ↗

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