Unit 1 L13: Conservation of Mass and the Bath Bomb

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The jar on the scale is a

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system. When the coal burns, the molecules​

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and rearrange to form​ different molecules. These molecules are​

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with different​

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than the original substance (the coal). Some of these new substances are gases which we can't see. But even though we can't see them, all of the same atoms are there so the​

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of the jar stays the same.

Multiple Choice

Is the model of this reaction correct?

• Yes

• No, because it does not have the same TYPE of atoms before and after.

• No, because it does not have the same NUMBER of atoms before and after.

Multiple Choice

Does this model show a chemical or physical change? Is mass conserved (in other words, it has the same number of atoms before and after)?

• A chemical change that conserves mass

• A chemical change that does NOT conserve mass

• A physical change that conserves mass.

• A chemical change that does NOT conserve mass.

Multiple Choice

Which substance is missing from the model?

• Oxygen (O₂)

• Ammonia (NH₃)

• potassium iodide (KI)

• sodium chloride (NaCl)

Open Ended

According to the scale, the mass after the reaction is less than the before. This seems to violate the Law of Conservation of Mass! Where did the missing mass go?

Labelling

Label the substances in the reactants and possible products in the bath bomb reaction.

Drag labels to their correct position on the image

Baking soda and citric acid

Carbon dioxide, nitrogen or argon

Multiple Select

Look carefully at the reactants - water, baking soda, and citric acid. What elements are they made up of? Select ALL that apply.

• hydrogen

• carbon

• sodium

• oxygen

• nitrogen

Multiple Choice

Look carefully at the reactants. Which of our 3 gases is the only one that could possibly be a product of this reaction?

• argon

• carbon dioxide (CO₂)

• nitrogen (N₂)

Open Ended

Explain why carbon dioxide could be, but nitrogen and argon can not, be the bath bomb gas.

Multiple Choice

Is the white substance that has been left behind one of the reactants (baking soda or citric acid), or is it a new substance? 

• baking soda

• citric acid

• a new substance

Multiple Choice

If the white substance isn’t one of the reactants (citric acid and baking soda) what could it be?  

• sodium citrate

• sodium nitrate

• ammonium nitrate

Open Ended

Why is sodium citrate the only one of those compounds that it could be?

Labelling

Label the reactants and products of the bath bomb reaction.

Drag labels to their correct position on the image

carbon dioxide

water

citric acid

sodium citrate

Multiple Choice

Based on what you have learned about conservation of mass and chemical reactions, which model of the bath bomb reaction could be correct?

• A

• B

Open Ended

Explain why the MODEL B must be the correct model.