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Free scope and sequences, TEKS breakdowns, phenomenon ideas, and engagement activities for the 2024 Texas science standards.

I'm Chris Kesler, a former award-winning Texas middle school science teacher. This is the site I wish I'd had in the classroom. One hub with TEKS breakdowns, scope and sequences, phenomenon starters, engagement ideas, and resources, all aligned to the standards you actually teach.

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All standards updated for the 2024 TEKS revision

TEKS Details | Texas Hub Module

8th Grade TEKS Standards

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TEKS S.8.6E • Matter & Properties

Conservation in Reactions

The Standard

"Investigate how mass is conserved in chemical reactions and relate conservation of mass to the rearrangement of atoms using chemical equations, including photosynthesis. Readiness Standard."

💡 What This Standard Actually Means

The Key Verb

"Investigate and model". Students run reactions, measure mass, and build simple models that show atoms being rearranged rather than created or destroyed. The standard's "including" list signals where to focus your students: balancing simple chemical equations to show that the same number of atoms of each element is present before and after a reaction. Students should be able to identify and explain why a balanced equation matches the law of conservation of mass. Instruction can take many forms, such as atom counts, before-and-after diagrams, and bar scales of mass.

The Law of Conservation of Mass says matter is neither created nor destroyed in a chemical reaction. The atoms that start the reaction are all still there at the end. They're just rearranged into new combinations. Antoine Lavoisier (late 1700s) is the scientist most associated with this law, which became a foundation for modern chemistry.

When students write a chemical equation, it should show that atom count. If 2 atoms of hydrogen plus 1 atom of oxygen go in, they should be able to find 2 hydrogens and 1 oxygen somewhere in the products. Balancing an equation means adding coefficients (the big numbers in front of the formulas) so each side has the same count of every element. The subscripts (the small numbers inside a formula) cannot be changed to balance an equation, because changing a subscript changes the substance itself. H2O is water. H2O2 is hydrogen peroxide. Different formula, different substance.

The core understanding students should walk away with is that atoms get rearranged in reactions, but the total count of each type of atom (and therefore the total mass) stays the same. A balanced equation is how chemists prove it on paper.

💬 From Chris's Classroom

I used to introduce conservation of mass with the baking soda and vinegar reaction in an open cup. Students would mass it before and after and then get confused because the mass went down. That's my fault for not sealing the bag. The fix that changed everything was doing the same reaction in a sealed zip-top bag. Mass before, mass after, identical within a gram. Then I'd open the bag and let the gas out, and mass it again. Now it's lighter. The atoms didn't disappear, they just floated out of the container. That contrast drove the concept home in a way no lecture ever could.

⚠️ Misconceptions Your Students May Have

These are some of the most common misconceptions. Knowing what to look for can help you get ahead of them.

"When something burns, the mass is destroyed"

✓

When a piece of paper burns, the mass doesn't vanish. The carbon and hydrogen in the paper combine with oxygen from the air and form carbon dioxide and water vapor, which float away as gas. If you could catch every bit of ash, smoke, and gas and weigh it with the oxygen that was consumed, the total mass would match the starting materials.

"You can balance an equation by changing the subscripts"

✓

This is one of the biggest errors students make. Subscripts are part of the chemical formula, and changing them changes the substance itself. H2O is water. H2O2 is hydrogen peroxide, which is a completely different compound. Balancing is done by adjusting coefficients, the big numbers placed in front of each formula, not by rewriting the formulas themselves.

"Gas isn't really matter, so it doesn't count toward the mass"

✓

Gases are matter. They have mass and take up space. A balloon full of air weighs more than an empty balloon. When a reaction produces or consumes a gas, that gas must be counted in the mass total. Sealing the reaction in a bag or closed flask is the best way to show students this in the classroom.

"A chemical reaction creates brand new atoms"

✓

Chemical reactions rearrange existing atoms into new combinations. They do not create or destroy atoms. If two oxygen atoms and four hydrogen atoms enter a reaction, two oxygens and four hydrogens come out the other side, just bonded differently. This is literally the point of a balanced equation.

📓 Teaching Resources for 8.6E

These resources are aligned to this standard.

Complete 5E Lesson

Conservation in Reactions Complete Science Lesson

The full unit for 8.6E: differentiated station labs, editable presentations, interactive notebooks (English + Spanish), student-choice projects, and assessments. Built on the 5E model.

⏱ Best for: Full unit coverage • Multiple class periods

Station Lab

Conservation in Reactions Station Lab

9-station hands-on lab covering conservation of mass and balanced equations with input stations (Explore It!, Watch It!, Read It!, Research It!) and output stations (Organize It!, Illustrate It!, Write It!, Assess It!). Print and digital. English and Spanish.

🔬 Best for: Core instruction • 1-2 class periods

Student Choice Projects

Conservation in Reactions Student Choice Projects

Choice board with nine project options plus a "design your own" pathway. Students demonstrate their understanding of conservation of mass and balanced equations through writing, building, illustrating, presenting, or digital formats.

🎓 Best for: Project-based assessment • 2-3 class periods

🌎 Phenomenon Ideas for 8.6E

Use these real-world phenomena to anchor your lesson. Show students the phenomenon first, let them wonder, then build toward Conservation in Reactions as the explanation.

🔎

Phenomenon 1

Burning a Marshmallow

Hold a marshmallow over a flame and it puffs up, turns brown, and shrinks to a charred blob. Most of the original marshmallow seems to be gone. If you weigh the burned piece, it's lighter than when you started. At first glance, it looks like mass was destroyed.

💬 Discussion Prompt

"Where did the rest of the marshmallow go? If atoms can't be created or destroyed in a chemical reaction, what must have happened to the material that seems missing?"

🔎

Phenomenon 2

Rust on a Bike Left in the Rain

A bike frame left outside through a wet winter ends up coated in red-brown rust. The rust flakes off and the frame looks thinner. Here's the surprising part: if you could measure it carefully, a rusted piece of iron weighs more than the clean piece did. Rust adds mass instead of removing it.

💬 Discussion Prompt

"If the iron looks like it's falling apart, why does the rusted piece weigh more than the original? What might be combining with the iron to create the rust?"

🔎

Phenomenon 3

Baking Soda and Vinegar in a Sealed Bag

Put baking soda and vinegar in a sealed zip-top bag. Weigh the whole thing. Mix them. The bag puffs up with gas. Weigh it again. The mass is the same. Now open the bag and let the gas out, then weigh it. The mass has dropped. The reaction didn't "lose" anything. The gas just escaped the container.

💬 Discussion Prompt

"Why does the mass stay the same in the sealed bag but change when the bag is opened? What does this tell you about what's happening to the atoms during the reaction?"

💡 Free Engagement Ideas for 8.6E

Sealed Bag Reaction Challenge

Give each group a zip-top bag, a spoonful of baking soda, and a small cup with vinegar inside the bag. Mass it on a digital scale. Seal the bag, then tip the cup to mix. Mass it again while the bag is puffed up. The numbers should match. Now open the bag, let the gas escape, and mass it a third time.

Materials: Zip-top bags, baking soda, vinegar, small cups, digital scale

Atom Count with Paperclips

Use two colors of paperclips to represent hydrogen and oxygen. Students build "reactants" on one side of a line and "products" on the other. Start with a simple unbalanced equation and have students add coefficients (represented by additional paperclip molecules) until the counts match. Makes balancing tactile.

Materials: Paperclips in 2 or 3 colors, index cards, markers

Steel Wool Burn Mass Challenge

Give each group a small piece of fine steel wool. Mass it. Then (with safety glasses and teacher supervision) use a battery terminal to light the steel wool. The steel wool ends up darker and more brittle but has actually gained a tiny amount of mass because it combined with oxygen. Use a sensitive scale to show the gain.

Materials: Fine steel wool (000 or finer), 9-volt battery, fireproof dish, sensitive scale, safety glasses

Coefficient vs. Subscript Sort

Write a dozen chemical formulas on index cards, some correct and some with subscripts secretly changed. Students work in pairs to identify the real formula versus the altered one and write out which atom count is different. Reinforces that subscripts define the substance and cannot be changed to balance an equation.

Materials: Index cards, markers, periodic table

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Texas Science Teacher Resource Hub

🚀 Jump to Your Grade

8th Grade TEKS Standards

Conservation in Reactions

💡 What This Standard Actually Means

⚠️ Misconceptions Your Students May Have

📓 Teaching Resources for 8.6E

🌎 Phenomenon Ideas for 8.6E

Burning a Marshmallow

Rust on a Bike Left in the Rain

Baking Soda and Vinegar in a Sealed Bag

💡 Free Engagement Ideas for 8.6E

Sealed Bag Reaction Challenge

Atom Count with Paperclips

Steel Wool Burn Mass Challenge

Coefficient vs. Subscript Sort

Year-at-a-Glance Pacing Guides

Trusted Across Texas

Texas Schools and DistrictsLove Kesler Science

What Teachers Are Saying

Give Your Science Teachers Everything They Need

See It in Action

Texas Schools and Districts
Love Kesler Science