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Design Challenge: A Cold Pack for the Skate Park

Grade 7 physical science: use test data to evaluate and improve a baking soda and citric acid cold pack for a skate park first-aid kit.

Grade 7ScienceInteractive · Printable

Aligned toMS-PS1-6

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What’s included

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

Details

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

About this worksheet

What students practice

Students use test data to judge cold-pack designs against criteria and constraints.
Students explain that a reaction that absorbs thermal energy cools its surroundings.
Students plan a fair next test to improve a design.

How to use

Go over the criteria in paragraph 2 together before students read the tables. The last question can be answered in writing or argued in pairs.

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 Cold Pack for the Skate Park

Test and improve a cold pack that absorbs thermal energy through a chemical reaction.

Test 1: How much powder?

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

Cool Packs for Bumps and Bruises

1The skate club at Westlake Middle School meets at the city skate park every Thursday. Falls on the ramps often leave riders with bumped knees and elbows, and the first-aid box at the park has no way to keep ice cold. The club's adviser, Ms. Chidinma Eze, suggested a design challenge: build a cold pack that becomes cold only when it is needed.

2The club agreed on criteria and constraints with the park's first-aid staff. The pack must reach 15 °C or colder and stay at or below 15 °C for at least 10 minutes. It must not leak. It must fit in the first-aid box, which holds bags no larger than 1 liter, and the ingredients must cost less than $1 per pack. Only food-safe ingredients may be used.

3The club chose two kitchen powders: baking soda and citric acid. When both dissolve in water, they react and form new substances, including carbon dioxide gas. Each pack was a zip bag holding 100 mL of water at 22 °C. A small one-way valve near the top of the bag let gas out but kept the liquid in, as long as no foam reached it. The powders were sealed in a small inner pouch inside the bag. Squeezing the bag broke the pouch and started the reaction. A thin temperature probe was sealed into each bag. Ms. Eze measured the powders, and everyone wore safety goggles.

4In Test 1, team members Tomás Reyes and Aiyana Whitehorse used 0.5-liter bags and changed the mass of the powders, always using equal masses of baking soda and citric acid. They made three packs of each recipe and recorded the averages. Each of the two powders cost about 2 cents per gram.

5In Test 2, they used the 20 g recipe and changed only the size of the bag. Tomás noticed that every bag puffed up and that gas hissed out of the valve as the powders reacted. In every bag that leaked, foam from the bubbles had risen up to the valve.