Worksheet

Design Challenge: A Warm Thruster Model for Space Day

Grade 7 physical science: use test data on peroxide concentration and amount to choose and improve a yeast-powered thruster model that releases thermal energy.

Grade 7ScienceInteractive · Printable

Aligned toMS-PS1-6

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1 NGSS standard
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10 questions
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Details

Format: Interactive · Printable
Grade: Grade 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Short answer

About this worksheet

What students practice

Students analyze test data to see how a reactant's concentration and amount change the energy a device releases.
Students judge designs against criteria for temperature, time and amount.
Students recommend and justify a design and a next test.

How to use

Read the criteria in paragraph 3 aloud and have students copy them before they study the tables. A teacher demonstration with 3% peroxide and yeast, with goggles, helps students picture the tests.

Curriculum

NGSS standard covered

MS-PS1-6

Design and test a device that releases or absorbs thermal energy through a chemical process, such as a hand warmer.

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Name Date

Design Challenge: A Warm Thruster Model for Space Day

Test concentration and amount to design a device that releases thermal energy.

Test 1: How strong a solution?

Read the passage and study Table 1. Then answer the questions.

A Thruster You Can Touch

1Each spring, the aerospace club at Brightwater Middle School runs a table at the public library's Space Day. This year, club members Oluwaseun Adebayo and Mira Halvorsen-Cruz wanted to show how some real rockets and spacecraft thrusters have used hydrogen peroxide. In those engines, very concentrated hydrogen peroxide flows over a catalyst, a substance that speeds up a reaction without being used up. The peroxide breaks down into water vapor and oxygen gas, the reaction releases a large amount of thermal energy, and the hot gases rush out of a nozzle.

2The club's model uses much safer materials: drugstore hydrogen peroxide solution, which is mostly water, and dry baker's yeast, which contains a natural catalyst. The reaction is 2 H₂O₂ → 2 H₂O + O₂. Oxygen bubbles foam up inside an open 1-liter plastic bottle that stands on a tray, and the liquid warms up. The club adviser, Ms. Ayumi Hayashi, mixes the yeast with water and pours it into the peroxide. Everyone at the table wears goggles and gloves, and no flames are allowed nearby.

3The club set four criteria for the model. The liquid must reach at least 30 °C, so visitors can clearly feel the warm bottle. It must stay at or above 30 °C for at least 3 minutes, long enough for a line of visitors to touch it. The foam must stay inside the bottle. Each demonstration may use no more than 250 mL of peroxide solution, so the club's supplies last the whole day.

4In Test 1, the club changed the concentration of the peroxide. The drugstore solution is 3% hydrogen peroxide, meaning 3 g of hydrogen peroxide in every 100 g of solution. Ms. Hayashi mixed some of it with water to make 2% and 1% solutions. Every trial used 100 mL of solution at 20 °C and 5 g of yeast mixed into 20 mL of water at 20 °C. A temperature probe in the liquid recorded the highest temperature and the number of minutes at or above 30 °C. The club ran each test three times and recorded the averages.

5In Test 2, they kept the 3% solution and changed the amount, using 5 g of yeast for every 100 mL of solution. All of the solutions in both tests started at 20 °C.

Table 1. Test 1: Concentration (100 mL, average of 3 trials)
Peroxide solution	Highest temp (°C)	Minutes at/above 30 °C	Foam stayed inside?
1%	24	0	Yes
2%	28	0	Yes
3%	32	2	Yes

Use Table 1 and paragraph 4.

The 3% solution warmed up by °C from its starting temperature.

Which pattern does Table 1 show?

A. Each solution warmed up about the same, so concentration made little difference.
B. Each extra 1% of peroxide raised the highest temperature by about 4 °C.
C. The 2% solution warmed up about twice as much as the 3% solution.
D. The weaker solutions warmed up more, because they had more water to heat.

Where did the thermal energy that warmed the liquid come from?

A. It was made by the bottle as the foam rubbed against its plastic walls.
B. It came from the yeast water, which was warmer than the peroxide.
C. It flowed in from the room air, which the oxygen bubbles carried down.
D. It was released by the reaction as the hydrogen peroxide broke down.

Why did every trial in Test 1 use 100 mL of solution, 5 g of yeast and liquids that started at 20 °C?

A. So that the concentration was the only thing that changed
B. So the 1% solution could react as quickly as the 3% solution
C. So that each trial would release the same amount of energy
D. So that the foam would reach the same height in every trial

Test 2: How much solution?

Use Table 2 and the criteria in paragraph 3 to answer the questions.

Table 2. Test 2: Amount of 3% Solution (average of 3 trials)
Solution (mL)	Highest temp (°C)	Minutes at/above 30 °C	Foam stayed inside?
50	29	0	Yes
100	32	2	Yes
200	33	6	Yes
300	33	9	No

Which design in Table 2 meets all four criteria in paragraph 3?

A. 300 mL of 3% solution
B. 50 mL of 3% solution
C. 200 mL of 3% solution
D. 100 mL of 3% solution

From 100 mL to 300 mL, the highest temperature hardly changed, but the warmth lasted much longer. Which explanation fits the data best?

A. More solution released more energy but also had more liquid to warm, so it cooled more slowly.
B. More solution holds more cold at the start, so the bottle needed more time to cool down.
C. More solution means a stronger solution, so the reaction made the liquid hotter for longer.
D. More yeast was used up in the larger trials, so it released its own energy into the liquid.

The club plans 12 demonstrations with the design that meets all four criteria. Drugstore peroxide comes in 500 mL bottles.

The club needs mL of 3% solution, so it must buy at least bottles.

Suppose the peroxide and yeast water for the 200 mL design had been stored in a cold garage and started at 10 °C instead of 20 °C. Based on the tests, what would most likely happen?

A. The liquid would reach about 43 °C, because a colder start makes the reaction release more energy.
B. The liquid would still reach about 33 °C, because the amount of peroxide is the same.
C. The liquid would reach only about 23 °C, so the design would fail the 30 °C criterion.
D. The liquid would stay at 10 °C, because the yeast catalyst stops working below 20 °C.

Mira wonders whether using more yeast would change the results. Which next test is a fair test of her question?

A. Use more yeast with 300 mL of solution and less yeast with 100 mL, then compare them.
B. Use 200 mL of 3% solution at 20 °C every time, and change only the grams of yeast.
C. Test 10 g of yeast on a warm day and 5 g of yeast on a cold day in the garage.
D. Change the grams of yeast and the peroxide concentration together to save time.

10.

Write a recommendation for the club's Space Day model. State which design they should use, support your claim with data from Table 1 and Table 2 and the four criteria, explain where the thermal energy comes from and why the amount of solution changed how long the bottle stayed warm, and suggest one more test.