Hot Bottles and Melting Snow for a Snow-Camping Trip

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Hot Bottles and Melting Snow for a Snow-Camping Trip

Investigate how mass, type of matter and energy transferred change temperature.

Part 1: The sleeping-bag warmer test

Read the passage and Table 1. Use them to answer questions 1–5.

Getting Ready for a Night on the Snow

1In February, Rosalind Tanaka and her family will spend two nights in tents at a state park, with snow on the ground and nights well below freezing. Her aunt, Ilse Moreau, has snow camped for years. She told Rosalind that many campers fill a bottle with hot water at bedtime and tuck it into the foot of the sleeping bag. Rosalind wondered whether a bottle of water was really the best choice, or whether a bag of sand or a smooth stone heated by the fire would work as well.

2Before the trip, Rosalind tested four warmers in her family's unheated shed, where the air stayed close to 0 °C all night. She used a 1 kg bottle of water, a 0.5 kg bottle of water, a 1 kg cloth bag of dry sand and a 1 kg stone. Her aunt warmed each one to 60 °C, filling the bottles with hot water and heating the sand bag and the stone in a low oven. Rosalind placed each warmer in the middle of an identical rolled-up sleeping bag, with a thermometer probe touching it, and read the temperatures every hour for 4 hours.

3Aunt Ilse also told her that melting snow for drinking water uses a lot of stove fuel. Back at school, Rosalind asked her science teacher whether ice really takes more energy than cold water. They set up foam cups with lids, each holding warm water at 40 °C. Into each cup they dropped either ice cubes or ice water, both at 0 °C, and stirred until all the ice had melted. Then they read the final temperature. Each trial was done twice, and the two results were averaged.

Table 1: Warmer Test (shed air about 0 °C; every warmer starts at 60 °C)
Hours	1 kg water (°C)	0.5 kg water (°C)	1 kg sand (°C)	1 kg stone (°C)
0	60	60	60	60
1	52	50	38	40
2	45	42	25	27
3	39	35	16	18
4	34	29	10	12

1.

Use Table 1.

During the 4 hours, the 1 kg bottle of water cooled by °C.

2.

In the first hour, the 1 kg water bottle cooled by 8 °C and the 1 kg sand bag cooled by 22 °C. Both started at 60 °C in identical sleeping bags in the same shed, so energy likely left each one at about the same rate at first. Which is the best explanation for the difference?

A. The sand started with less thermal energy, since it was cooler than the water at the start.B. For about the same energy given off, the temperature of sand drops more than that of water.C. The sand passed its cold to the sleeping bag, which made the sand cool off even faster.D. The water's sleeping bag made extra thermal energy, which kept the water from cooling.

3.

After 4 hours, the 0.5 kg bottle had cooled by 31 °C and the 1 kg bottle by 26 °C. Rosalind says, "The small bottle cooled more, so it gave off more energy to its sleeping bag." Which is the best reply?

A. You're right: the warmer that drops by more degrees is the one that gave off more energy.B. Not quite: they gave off the same energy, because both bottles started at 60 °C.C. Not quite: the big bottle has twice the water and cooled almost as much, so it likely gave off more.D. Not quite: the big bottle gave off less, because it was still the warmer of the two at 4 hours.

4.

Use Table 1.

At 4 hours, the 1 kg water bottle was °C warmer than the 1 kg stone.

5.

Circle each comparison from Table 1 that is a fair way to show that the type of matter affects how much a warmer's temperature changes.

Part 2: Ice in warm water

Use paragraph 3 and Table 2 to answer questions 6–11.

Table 2: Ice Trials (warm water at 40 °C; ice and ice water at 0 °C)
Trial	Warm water (g)	What was added	Final temp (°C)
1	200	20 g of ice	29
2	200	40 g of ice	20
3	200	60 g of ice	12
4	200	20 g of ice water	36
5	400	40 g of ice	29

6.

Use Table 2.

In Trial 2, the warm water cooled by °C.

7.

What do Trials 1, 2 and 3 show?

A. More ice took in more energy from the warm water, so the final temperature was lower.B. More ice gave more cold to the warm water, so the final temperature dropped further.C. The final temperature stayed about the same, since the warm water started at 40 °C each time.D. More ice spread the water's energy thinner, so energy was lost and the water cooled.

8.

In Trials 1 and 4, the same mass was added at the same temperature, 0 °C. Yet the ice cooled the water 7 °C more than the ice water did. Which is the best explanation?

A. The ice cubes were colder than the ice water, even though both of them read 0 °C.B. The ice had more mass than the ice water, so it took in more of the energy.C. The ice water held less cold, since some of its cold had already melted away.D. Melting took in energy from the warm water before the meltwater began to warm.

9.

Trials 1 and 5 both ended at 29 °C. Which statement explains why?

A. Trial 5 had twice the warm water to give energy and twice the ice to take it in.B. The extra warm water in Trial 5 kept its ice from melting, so no extra energy moved.C. Both trials used warm water at 40 °C, and that starting temperature set the final temperature.D. Both trials had the same mass of ice, so the ice took in the same energy each time.

10.

Use the patterns in Trials 1, 2 and 5 to make a prediction. Rosalind adds 80 g of ice at 0 °C to 400 g of warm water at 40 °C and stirs until it melts.

The final temperature would be about °C.

11.

A camper says, "Snow is just frozen water at 0 °C. Melting a pot of snow and warming it to drinking temperature takes the same stove energy as warming the same mass of 0 °C creek water." Do you agree? Write a claim, give evidence from Table 2, and explain your reasoning about energy and temperature change.