Melting Away

This week we investigated what happens to the temperature of ice as it melts. We measured the temperature every minutes for 10 minutes, while checking to see if the water was solid, liquid, or gas.

Initially the temperature was a FREEZING -10° C. Not surprisingly the temperature started to rise, but then something funny happened.  As the temperature approached 0° C, it stopped changing. Yet, the ice was still melting. Clearly heat from the surroundings was being absorbed by the ice, but to look at the temperature, you'd never know it. Then, as soon as all the ice was melted into water, the temperature started to climb once again. 

From this experiment we learned two things: 
1) The freezing point of water is 0° C
2) At this temperature, the energy flowing from the environment into the ice is being used to change the water from a solid to a liquid, resulting in a constant temperature until all the water is in the liquid state.  

We see the same thing happen as substances move between liquid and gas states.

Hot and Cold

This week we learned how to use a thermometer. First we measured some temperatures in and around the kitchen: the freezer, the fridge, room temperature, etc. Then we went out into the yard to find the hottest and coldest spots. We were surprised to find as much as a 5 °C difference between sunny and shady areas.

General Science and Biology: Solutions

This week we learned about solutions, that is liquid mixtures. In particular we wanted to know whether water temperature affects how well something dissolves. First the kids compared the time it takes to dissolve a couple drops of food coloring in different water temperatures. Then they tried to see how much sugar they could stir into solution, once again comparing different water temperatures. They concluded that hot water is much more effective at dissolving solutes (that's fancy-talk for stuff).

In the biology group we also noted that the final volume of the sugar solution was surprisingly LESS than the sum of the initial water volume plus the sugar. Part of what happens when you dissolve something is that it reacts chemically with the solvent (fancy-talk for liquid) and/or fits into the spaces within the molecules themselves.