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Kitchen Systems: Spice Tins, Flour and Stored Energy

Grade 8 potential energy practice: use force-sensor data on a magnetic spice strip, a flour bag and plastic wrap to model stored energy.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS3-2

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
11 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use energy data to model how the distance between attracting objects changes stored energy.
Students compare a magnetic system, a gravity system and an electric system and explain where the energy is stored.

How to use

Read the project notes together and point out that the energy column is energy put in while pulling slowly. Students then work through both tables and finish with the claim-evidence-reasoning task.

Curriculum

NGSS standard covered

MS-PS3-2

Model how changing the distance between interacting objects changes the potential energy stored in the system.

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Kitchen Systems: Spice Tins, Flour and Stored Energy

Use force-sensor data from a home kitchen to model how distance changes stored energy.

Part 1: The spice lid and the magnetic strip

Read Teodora's project notes. Use paragraphs 2 and 3 and Table 1 to answer questions 1–5.

Energy Hiding in the Kitchen

1Teodora Marchand's eighth-grade class was studying potential energy, the energy stored in a system of objects that pull or push on each other without touching. For a home project, Mr. Lars Bettencourt asked each student to find systems in their own kitchen and test how the distance between two objects changes the energy stored in the system. Teodora chose the magnetic strip that holds her family's spice tins and the heavy bag of flour her dad keeps in the pantry.

2The spice tins have steel lids, and the strip on the wall holds a row of strong magnets, so each lid and the strip attract each other. Teodora borrowed a force sensor from school and clipped it to a lid resting against the strip. She pulled the lid straight away from the strip and stopped at each gap in Table 1. She pulled very slowly, so the lid gained almost no speed, and nearly all the energy she put in was stored in the system of the lid and the strip. The sensor's app recorded how hard she was pulling at each gap and added up the energy she had put in since the lid left the strip. She did three pulls and averaged the results.

3Next, she held a lid still at different gaps and let it go. From a 1 mm gap, the lid jumped back onto the strip with a soft tap. From a 4 mm gap, it hit the strip with a sharp click that her dad heard from the next room.

4For the second system, Teodora used a 2.0 kg bag of flour and Earth, which attract each other through gravity. The pantry has four shelves, and each shelf is 0.5 m above the one below it. She hooked the force sensor to the bag and lifted it slowly from the floor to each shelf. The pull stayed at about 19.6 N the whole way up, and the app again added up the energy she put in. Table 2 shows the energy stored in the flour–Earth system at each shelf, compared with the bag sitting on the floor.

5Last, she tore two long strips of plastic wrap from the roll. Pulling wrap off a roll often leaves both strips with the same kind of charge. When she held the strips side by side and pushed them toward each other, she could feel them push back. When she let go, they sprang apart.