course phy 202

course First we began with 150 mL of water at a temperature of 31C. 150mL of water is also 150 grams of water. We also began with 50ml or 50 grams of snow at a temperature of 0C. The snow was extracted from a shady area. We then added the snow thirty seconds later and the temperature of the snow/water mixture was 20C. After one minute the snow/water mixture was heating back up to room temperature and was 25.75C.

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20-31=-11C change in temperature for the water.

20-0=20C change in temperature for the snow.

We then ended up with 160mL of snow/water mixture, which can also be stated 160 grams of snow/water mixture.

The question was how many Joules to melt 1 gram of ice.

Frozen snow requires about 2J per gram to raise the temperature 1C.

I know that we were using 4.19J, would I still do this or would I use 2J?

4.19J*150g of water=628.5J/g

628.5J/g * -11C (change in temperature of the liquid water)= -6913.5J/g

This is the energy lost by the water.

To figure out energy gained by the snow we would have to take

4.19J * 10grams of snow = 41.9 Joules of energy gained by snow from the water.

That would be if there was a 1 degree change in the frozen water.

Did the snow change temperature while frozen?

No.

Did the snow change temperature after melting?

Yes. But then it was technically considered water right? So we would use 4.19 instead of 2J? Right? I'm confused about where this 2J is even supposed to come in at!!

(If the snow starts out below 0 Celsius, then while it heats up to that temperature, before it begins to melt, the 2 J per gram per degree will apply.)

Since the snow started out at 0 Celsius, then there is no need to multiply anything by 2J then right?

Right.

What energy change was associated with each?

41.9 Joules * -11 C (change in temperature of of the water)= -460.9 Joules of energy gained by snow from water.

(41.9 Joules would be for a 1 degree change. You multiplied by -11 degrees. Did the temperature of the snow change by -11 degrees?)

The water had a temperature change of -11 degrees. "

The original water changed by -11 degrees. However the temperature of the melted snow increases, and not by 11 degrees.

How much energy did the snow gain after melting?

How much did it gain in all from the original water?

How much did it therefore gain in the melting process?

How much energy per gram did it therefore take to actually melt the snow?

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