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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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what are all types of reactions?(1 vote)- Great question!
Here are a few types of reactions you need to know at the high school level.
1. Synthesis (Combination) Reactions:
• What Happens: Two or more substances combine to form one new substance.
• Example: When hydrogen gas reacts with oxygen gas to make water.
• Equation: 2H₂ + O₂ → 2H₂O
2. Decomposition Reactions:
• What Happens: One substance breaks down into two or more simpler substances.
• Example: When water breaks down into hydrogen and oxygen gas.
• Equation: 2H₂O → 2H₂ + O₂
3. Single Replacement (Displacement) Reactions:
• What Happens: One element replaces another in a compound.
• Example: When zinc reacts with hydrochloric acid, replacing hydrogen.
• Equation: Zn + 2HCl → ZnCl₂ + H₂
4. Double Replacement (Metathesis) Reactions:
• What Happens: The ions of two compounds exchange places to form two new compounds.
• Example: When sodium sulfate reacts with barium chloride to form barium sulfate and sodium chloride.
• Equation: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
5. Combustion Reactions:
• What Happens: A substance (usually containing carbon) reacts with oxygen to produce carbon dioxide and water, releasing energy.
• Example: When methane burns in oxygen.
• Equation: CH₄ + 2O₂ → CO₂ + 2H₂O
6. Neutralization Reactions:
• What Happens: An acid reacts with a base to produce a salt and water.
• Example: When hydrochloric acid reacts with sodium hydroxide.
• Equation: HCl + NaOH → NaCl + H₂O(1 vote)
Can you do this out of the classroom?(0 votes)