THE EFFECT OF SALT ON THE TIME IT TAKES ICE TO MELT Isabella Carswell (Year 7)
Science Faculty, The Illawarra Grammar School, Western Avenue, Mangerton, 2500 Results:
Discussion This investigation, that aimed to determine the effect of different amounts of salt (sodium chloride) on ice, found that the more salt (sodium chloride) that was placed on the ice cube, the faster it melted. In other words, the ice melted more slowly with less salt (sodium chloride) on it. A plot graph (see above) of the two variables in the experiment (amount of salt and average time of ice melting) showed the data had a clear negative relationship and a line of best fit suggested a linear trend. In other words, the data shows a decreasing straight line that is directly related to the increase in salt placed on the ice decreases the time taken to melt. Therefore, the results supported the original hypothesis that the ice cube with the most salt (sodium chloride) added will melt faster.
People who live in snowy conditions, such as the Northern Hemisphere, use salt to melt ice on roads so that the roads are safer to drive on, but why does this happen? Salt (sodium chloride) lowers the freezing point of water making it impossible to freeze at 0 degrees Celsius with salt on it. This is because the salt particles interfere with the water (H2O) particles obstructing them from bonding and forming ice. When you dissolve table salt (sodium chloride) in water the sodium and chloride ions separate so the particles become small and move in between the water (H2O) molecules. The reason the more salt (sodium chloride) added to the ice cube creates a difference in the time it took to melt in my experiment, is because the more salt in or on the water/ice, the lower the freezing point becomes making the 1tsp of saltwater melt faster as its freezing point is further away from zero degrees, the usual freezing point of water. 7
