OwlSheets Students

Two Science Fair Projects, One Heater

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Two Science Fair Projects, One Heater

Use repeated heater trials and a particle model to explain how energy and mass change water's temperature.

Part 1: The two investigations

Read the passage and use both tables to answer questions 1–5.

Sharing a Science Fair Table

1At the Westfield Middle School science fair, sixth graders Hana Watanabe and Tomasz Kral shared a table and a big question: how do the amount of water and the amount of energy put into it change how much the water warms up? They used the same equipment: a foam cup with a lid, a small 12-volt heater that sits in the water and gives off 42 J of energy for each second it runs, a stirring rod and a digital thermometer. Their teacher, Mr. Kwabena Osterhout, plugged the heater in and took it out for every trial, so the students never touched the hot coil.

2Every trial started with water at 21 °C. The students stirred the water the whole time, read the highest temperature after the heater was switched off and ran each test three times. Hana always ran the heater for 120 s, but she changed the mass of water in the cup. Tomasz always used 200 g of water, but he changed how long the heater ran.

3When Hana checked her notes after the fair, she saw a problem. During trial 3 with 200 g of water, she had written: "thermometer tip resting on the heater coil, not hanging in the water."

4Mr. Osterhout reminded the students that water is made of particles far too small to see, and that the particles are always moving. The temperature of the water is a measure of the average kinetic energy of its particles: the faster the particles move on average, the higher the temperature.

Hana's Tests: Temperature Change With the Heater On for 120 s
Water (g)	Trial 1 (°C)	Trial 2 (°C)	Trial 3 (°C)	Average (°C)
100	11.6	11.4	11.5	11.5
150	7.6	7.8	7.7	7.7
200	5.9	5.7	8.6	?
300	4	3.8	3.9	3.9

Tomasz's Tests: 200 g of Water (average of 3 trials)
Heater on (s)	Temperature change (°C)
60	2.9
120	5.8
180	8.7
240	11.6

1.

Use paragraph 2. Match each variable to its role in the investigations.

2.

Use paragraph 3. Why should Hana leave trial 3 with 200 g of water out of her average?

A. Two trials give a more exact average than three trials do, so one should be dropped.B. The thermometer was reading the hot coil, not the water, so the result is not the water's change.C. Its temperature change was higher than 8 °C, which is too large for a cup of water.D. It was her last trial, and the heater gives off less energy each time it is used.

3.

Find the average of Hana's two good trials with 200 g of water. Do not round.

Average temperature change for 200 g: °C

4.

Which result from Tomasz's table best supports Hana's choice to leave out trial 3?

A. His 200 g, 120 s test rose by 5.8 °C, like Hana's two good 200 g trials.B. His 180 s test rose by 8.7 °C, which matches Hana's 200 g, 120 s trial 3.C. His 60 s test rose by 2.9 °C, which is about half of Hana's trial 3.D. His 240 s test rose by 11.6 °C, close to the 8.6 °C of Hana's trial 3.

5.

Use the averages in Hana's table. Compare 100 g of water with 300 g of water. Round to the nearest whole number.

With the same 120 s of heating, the temperature change of 100 g of water was about times the temperature change of 300 g.

Part 2: Energy, mass and particles

Use both tables and paragraph 4 to answer questions 6–12.

6.

Which statement do Tomasz's results support?

A. The water warmed most in the first 60 s, and each later minute added a smaller change.B. Each extra 60 s of heating added about 2.9 °C, so the change grew in step with the energy.C. Each 60 s step added a larger temperature change than the step before it did.D. Doubling the heater time from 120 s to 240 s made the temperature change four times as large.

7.

Use paragraph 1. Energy from the heater = 42 J × the number of seconds it runs.

In Tomasz's 180 s test, the heater gave off J. In his 240 s test, it gave off J.

8.

Suppose Hana and Tomasz heat 400 g of water for 240 s, starting at 21 °C. Use both tables. Which prediction for the temperature change fits their results best?

A. About 11.6 °C, because the heater runs as long as in Tomasz's longest testB. About 2.9 °C, because the mass of water is twice as large as in Tomasz's testsC. About 5.8 °C, because twice the energy is shared by twice the mass of waterD. About 23.2 °C, because both the mass and the heater time are doubled

9.

Use paragraph 4. Hana's 100 g and 300 g cups got the same 120 s of heating, but the 300 g cup warmed much less. Which explanation fits the particle model best?

A. The same energy was shared among about three times as many particles, so their average speed rose less.B. The heater made fewer new particles in the 300 g cup, so there was less motion to measure.C. The particles in the 300 g cup were already moving faster at the start, so the heater sped them up less.D. The 300 g cup lost most of its energy through the lid, so its particles slowed down during heating.

10.

Use paragraph 4. Sort each event by what happens to the average kinetic energy of the particles of the water that is already in the cup.

11.

A judge asks whether the type of matter also changes how much a liquid warms. Which plan is a fair test of that question with the same equipment?

A. Heat 200 g of cooking oil for 240 s and compare it with 200 g of water heated for 120 s.B. Heat 300 g of cooking oil for 60 s and compare it with 100 g of water heated for 180 s.C. Heat 100 g of cooking oil for 120 s and compare it with 200 g of water heated for 120 s.D. Heat 200 g of cooking oil for 120 s and compare it with 200 g of water heated for 120 s.

12.

Hana's younger brother looks at her table and says, "The 300 g cup warmed less because all that extra water blocked the heater's energy from getting in." Do you agree? Write a claim, give evidence from both tables, and explain your reasoning using the particle model in paragraph 4.