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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

Click any standard to see what it means, how to teach it, where students get stuck, and aligned resources.

TEKS 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."

💡 What This Standard Actually Means

The Key Verb

"Investigate and relate". Students run reactions, measure mass, and then relate what they see back to the rearrangement of atoms using a chemical equation. The standard's "including" list signals what's required, not optional: students must work with photosynthesis (6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂) as one of the reactions they balance and explain. Whatever reaction they investigate, the goal is the same: students should be able to point at a balanced equation and say "the atoms on the left match the atoms on the right, so mass is conserved." 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 4 hydrogen atoms and 2 oxygen atoms go in (as in 2H₂ + O₂), they should be able to find 4 hydrogens and 2 oxygens somewhere in the products (in 2H₂O). 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. The TEKS specifically calls out photosynthesis as a required example on this page, so students should be comfortable counting atoms on both sides of 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ and explaining how a tree's mass comes mostly from the air, not the soil.

💬 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 4 hydrogen atoms and 2 oxygen atoms react (as in 2H₂ + O₂ → 2H₂O), the products will still contain 4 hydrogens and 2 oxygens, just rearranged into new molecules. This is literally the point of a balanced equation.

📓 Teaching Resources for 8.6E

These resources are aligned to this standard.

FREE

Conservation in Reactions — I Can Poster Pack

Print-ready classroom poster pack for TEKS 8.6E. Includes the verbatim Texas standard plus student-language "I Can" statements broken into daily learning goals. Landscape letter, ready to print and post on your wall.

📍 Best for: Daily learning-goal board • Print and post

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

Hands-On Inquiry Lab

Chemical Reactions & Mass Hands-On Inquiry Lab

A hands-on inquiry investigation where students measure mass before and after a chemical reaction to test the law of conservation of mass. Includes student handouts, teacher guide, and materials list. 3 versions for differentiation. Both print and digital version included.

🧪 Best for: Inquiry-based investigation • 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

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🌎 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

Where Does the Mass of a Tree Come From?

A massive oak in the front yard weighs thousands of pounds. Ask students where all that wood came from and most of them will say "the soil" or "the roots." Back in the 1600s a scientist named Jan van Helmont planted a small willow in a pot, weighed the soil, watered it for five years, and weighed everything again. The tree had gained over 160 pounds. The soil had lost about 2 ounces. The wood didn't come from the dirt. It came from the air, through photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

💬 Discussion Prompt

"If almost none of a tree's mass comes from the soil, where do the atoms in the wood actually come from? Use the photosynthesis equation to explain how mass is conserved when a tree grows."

🔎

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

Photosynthesis Atom-Count Showdown

Write the photosynthesis equation across the top of a piece of paper: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Give each group three colors of dot stickers (or markers): one for carbon, one for hydrogen, one for oxygen. Students draw or stick the correct number of atoms for every molecule on the reactant side, then do the same on the product side. They tally each element and prove it matches: 6 C, 18 O, and 12 H on each side. Once they see it, have them try the same atom-count check on cellular respiration (the reverse equation) so they realize it works both directions.

Materials: Paper, colored dot stickers or markers in 3 colors, periodic table

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

100% Aligned Lessons for Every TEKS You Teach

🌎 Phenomenon Ideas for 8.6E

Burning a Marshmallow

Where Does the Mass of a Tree Come From?

Baking Soda and Vinegar in a Sealed Bag

💡 Free Engagement Ideas for 8.6E

Sealed Bag Reaction Challenge

Atom Count with Paperclips

Photosynthesis Atom-Count Showdown

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