R5.2.4 - Cluster #1

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R5.2.4 - Cluster #1

Where Did the Wood Go?

Have you ever sat around a blazing campfire? At the start of the night, you might place a giant, heavy log into the fire ring. It takes a lot of effort just to lift it! But the next morning, when the fire is completely out, all that is left is a tiny, lightweight pile of gray ash.

Where did all that heavy wood go? Did it magically disappear?

In science, there is a very important mathematical rule called the Law of Conservation of Matter. This rule says that matter (the stuff that makes up everything) cannot be created out of nothing, and it cannot be magically destroyed. Even when a substance is heated, cooled, mixed, or burned, the tiny particles of matter just change shape or form. The total weight of all the starting pieces must equal the total weight of the final pieces. The weight is always conserved (kept the exact same).

When wood burns, it goes through a chemical change. The solid wood turns into solid ash, but it also turns into heat, smoke, and invisible gases (like water vapor and carbon dioxide). Because a campfire is an open system, those gases float up into the sky. If you could somehow build a giant, fireproof bubble over the campfire to trap every single puff of smoke and invisible gas, and then weigh that giant bubble, it would weigh the exact same amount as the starting log and the air it used to burn!

The Laboratory Burn Test To prove this mathematical rule to her students, a scientist named Dr. Chen decides to burn small pieces of wood in her science lab. She runs two mathematical tests using a digital scale.

Test 1 (The Open System): She burns a piece of wood in an open glass beaker. The smoke floats away into the lab.
Test 2 (The Closed System): She places another piece of wood inside a special, heavy glass sphere that seals completely shut. Nothing can get in or out. She uses a laser to heat the wood from the outside until it burns into ash. All the smoke and gas get trapped inside the glass sphere.

Data Set A

Data Set B

In Test 1 (Open Beaker), the total starting weight was 150 grams, but the final weight was 105 grams. Based on the article, what happened to the missing 45 grams? *

1 point

A. The 45 grams of matter was destroyed by the fire.

B. The 45 grams turned into smoke and gas that floated out of the open beaker.

C. The glass beaker absorbed 45 grams of the wood.

D. The 45 grams turned into solid ash.

Look at Test 2 (Sealed Sphere). Why did the Total Final Weight perfectly match the Total Starting Weight (350 grams)? *

1 point

A. Because the glass trapped the smoke and invisible gases so the scale could still weigh them.

B. Because it wasn’t destroyed like it was in Test 1.

C. Because it absorbed the water from the air.

D. Because it absorbed the particles from the air.

Using computational thinking, which math problems correctly match the data from Data Set B? *

1 point

Test 1 Total Start: 100g + 50g = 150g.

Test 2 Total Start: 300g + 50g = 350g.

Test 1 Weight of Escaped Gas: 150g - 105g = 45g.

Test 2 Weight of Escaped Gas: 350g - 350g = 0g.

The wood in both tests weighed exactly 100g combined.

Required

Look at Data Set A (The Open Campfire). Why does the solid weight keep going down over time? *

1 point

Because it is an open system, so the new gases are blowing away in the wind.

Because solid wood is being converted into smoke and gas.

Because the wood particles are disappearing.

Because the wood is dissolving into the water from the soil..

Because matter is leaving the fire pit and joining the air.

Required

To prove that the Law of Conservation of Matter (matter is never created or destroyed) is true, scientists must measure the weight of which things? Select all that apply. *

1 point

Solids (like wood and ash)

Liquids (like melted water)

Gases (like trapped smoke or invisible carbon dioxide)

The containers holding the substances

The color of the fire

Required

You want to prove that gas has weight using a plastic bottle, a balloon, baking soda, and vinegar. If your empty bottle weighs 20g, your balloon weighs 5g, your vinegar weighs 40g, and your baking soda weighs 10g, what should the Total Starting Weight be? How can you use the balloon to make sure the Total Final Weight stays the exact same after they mix and fizz? *

1 point

Total Starting Weight = 75 grams. To make sure the final weight stays the exact same, I should place the balloon in the cup next to the bottle during the reaction. The gas will fill the room air, but because gas has no weight, the scale will still read 75 grams at the end.

Total Starting Weight = 75 grams. When I stretch the balloon over the bottle, the reaction creates gas that inflates the balloon. Because gas floats and carries things upward, the final weight will decrease to 70 grams as the balloon fills up.

Total Starting Weight = 75 grams (20 + 5 + 40 + 10). To make sure the final weight stays at exactly 75 grams, I must stretch the balloon over the mouth of the bottle before they mix. This creates a "closed system" that will trap the fizzing gas inside the balloon so it can be weighed by the scale.

Total Starting Weight = 50 grams (40g vinegar + 10g baking soda). To make sure the final weight stays the exact same, I must stretch the balloon over the top of the bottle. The gas will inflate the balloon, keeping the final chemical weight at 50 grams.

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