Temperature, particle motion, and how much the temperature changes

Answer Key - Grade 8 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   A heater gives sample B the same energy as sample A. Ari heats two samples of water with the same amount of energy. How many °C does sample B rise?

   4 °C
2. 2.

   A heater gives sample B the same energy as sample A. Two samples of milk get the same energy from a heater. How many °C does sample B rise, Esme?

   6 °C
3. 3.

   Assume no energy leaves the cup. Jun mixes the hot and cold water. Which final temperature is most reasonable?

   • 65 °C, since the hot water has the faster particles and those particles dominate the mixture
   • 50 °C, halfway between the two, since equal masses share the energy evenly
   • 20 °C, since the cold particles slow the hot ones down until the mixture matches the cold water
   • 100 °C, since the two starting temperatures add together when the samples are mixed
4. 4.

   Assume no energy leaves the cup. Luz claims the final temperature is always the average of the two starting temperatures. Does the table support that?

   • Yes: trial 1 matched the average, so the other two trials must have had measurement errors
   • No: only trial 1 matched the average, and the final temperature moved toward the larger mass
   • No: each final temperature should match the hot water's, since hot particles dominate a mixture
   • Yes: each final temperature sits between the two starting temperatures, which makes it an average

5. Read this first

   Three samples with the same energy (example data)

   sample	mass (g)	temperature rise (°C)
   A	100	20
   B	100	8
   C	100	12

6. 5.

   Milo gives three 100 g samples the same energy. Which material needs the most energy per degree of warming?

   • Sample B, since the same energy raised its temperature by the smallest amount
   • The three need equal energy per degree, since the heater gave each sample equal energy
   • Sample C, since its rise is in the middle, so it needs a middle amount of energy per degree
   • Sample A, since it rose the most, so it must have absorbed the most energy

7. Two samples with the same energy (example data)

   sample	mass (g)	temperature rise (°C)
   X	50	16
   Y	100	16

8. 6.

   Samples X and Y get the same energy and both rise 16 °C. Which material needs more energy per gram per degree, Noah?

   • Y, since a larger sample needs more energy per degree than a smaller sample made of the same material
   • Y, since it has more mass and so took in more energy from the heater than X did
   • X, since it has half the mass but rose just as much from the same energy
   • Neither: they are equal, since both samples rose by 16 °C from the same energy

9. Three samples with the same energy (example data)

   sample	mass (g)	temperature rise (°C)
   A	200	10
   B	100	10
   C	100	5

10. 7.

    All three samples get the same energy. Which material needs the most energy per gram per degree, Pia?

    • A and B tie, since both rose 10 °C and the heater gave each of them equal energy
    • B, since it rose 10 °C with just 100 g, so it absorbed the most energy of the three
    • A, since it has the most mass and so took in the most energy from the heater
    • C, since it warmed the least and had just 100 g to share the energy
11. 8.

    Ren plans a fair test of whether sand or water warms faster under a lamp. Which plan is best?

    • Use 100 g of each material in matching dishes under one lamp, but read each thermometer once at the end of 10 minutes instead of every minute
    • Use 100 g of each material in matching dishes, put both the same distance from one lamp, and read both thermometers every minute for 10 minutes
    • Use 100 g of each material in matching dishes, but set the sand closer to the lamp than the water since sand looks darker and slower to warm
    • Use 100 g of sand and 200 g of water in matching dishes under one lamp, so the water has enough mass to show a clear change on the thermometer

12. Lamp test, one dish of each (example data)

    material	mass (g)	minutes under the lamp	temperature rise (°C)
    Sand	100	10	22
    Water	200	10	8

13. 9.

    Tala says sand has a smaller specific heat than water. What change would make this test fair?

    • Test 100 g of water for 10 minutes, so that only the material differs between the two dishes
    • Keep both dishes as they are and report the result as certain, since the same lamp was used for both
    • Test 200 g of sand for 15 minutes, so that the sand has as much to warm up as the water has
    • Test 100 g of water for 20 minutes, so that it reaches the same temperature as the sand did
14. 10.

    Each dish held 100 g and sat under one lamp for 10 minutes. Each material was tested three times with 100 g under one lamp for 10 minutes. Which conclusion do the data support, Zee?

    • Water needs less energy per degree, since its rise was the smaller one in each of the three trials
    • The sand results vary from 22 °C to 25 °C, so no conclusion about the two materials is possible
    • Trial 1 settles it, since 22 °C against 11 °C is clear and the other two trials add nothing
    • Sand rose about twice as much as water in each trial, so sand needs less energy per degree