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Course: High school chemistry > Unit 3
Lesson 3: Activity: How can a big log turn into a tiny pile of ash when it burns?Activity: How can a big log turn into a tiny pile of ash when it burns?
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Activity: How can a big log turn into a tiny pile of ash when it burns?
If you’ve ever seen a piece of wood or paper burn, you may have noticed that most of it seems to “disappear” in this process. Maybe you’ve been watching a spy movie, and seen an undercover agent “destroy” a secret message by igniting the sheet of paper on which it was written. Or maybe you’ve built a campfire, only to observe the logs reduced to a small pile of ashes at the end of the night.
One of the fundamental laws of chemistry is that matter cannot be created or destroyed during a chemical reaction. So, how can we explain these scenarios where matter appears to be destroyed or to disappear? Where did it go? In this activity, you’ll investigate what happens to the amount of matter as substances undergo physical and chemical changes and use your knowledge to develop an explanation.
Overview
This activity is designed to be completed in two or three 45-minute class periods, with additional time required for follow-up creative projects. The activity consists of the following parts:
- Setting the stage—Students review fundamental concepts related to conservation of mass. (15 minutes)
- Investigation (Part 1)—Students observe and collect mass data for a sample of water as it changes from a solid to a liquid. Students model the experimentally observed conservation of mass using particle diagrams and a balanced chemical equation. (20 minutes)
- Investigation (Part 2)—Students observe changes and collect mass data when combining aqueous solutions of magnesium sulfate and sodium carbonate to form a precipitate. Students model the experimentally observed conservation of mass using particle diagrams and a balanced chemical equation. (35 minutes)
- Investigation (Part 3)—Students observe changes and collect mass data when combining solid sodium bicarbonate with an aqueous solution of acetic acid, first in an open system, and then in a closed system. Students analyze and interpret their experimental data to draw further conclusions about conservation of mass in chemical reactions. (45 minutes)
- Let's get creative!—Students apply their knowledge of conservation of mass to write a script or storyboard for a YouTube science show episode that addresses the misconception that mass "disappears" when a log burns. (45 minutes)
- Keep creating!—Students can choose from additional project ideas. Each project encourages students to combine scientific knowledge with creativity to produce something new.
Download the worksheets and get started today!
You can print out this activity or upload it to a digital classroom.
- Student activity guide (16 page worksheet)
- Teacher guide (step-by-step instructions)
NGSS performance expectations
HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
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