Conservation of Mass

What is the Law of Conservation of mass?

• Mass is created in a chemical reaction
• Mass is created in a physical change
• New chemicals formed from a chemical reaction have a larger overall mass than the original reactants
• Mass is never created or destroyed

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NGSS.MS-PS1-5

NGSS.MS-PS1-2

What will weigh more when a chemical change is complete?  The reactants before the chemical reaction, or the product after the reaction is complete?

• They both will weigh the same
• The product always weighs more than the reactant
• The reactant will weigh more than the product
• They both will loose mass after the reaction

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NGSS.MS-PS1-5

Suppose a reaction were to happen in an open container in a lab.  During the reaction, the scientist observes the chemicals bubble, and produce a gas.   During the analysis the scientist notices that the reactants weighed 20 g when he started, and the product weighed 18 g.  Explain what happened.  

• His chemical reaction defied the law of conservation of mass
• The product destroyed mass during the reaction
• The reactants created matter during the reaction
• The gas that was produced was not able to be weighed since the container was open.  

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NGSS.MS-PS1-5

NGSS.MS-PS1-2

Evidence of a chemical reaction include:

• Phase change
• No new substance
• Bubbles forming
• Shape change

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NGSS.MS-PS1-2

Evidence of a chemical change does NOT include:

• New substances
• Heat produced
• Phase change
• Light produced

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NGSS.MS-PS1-2

How is a physical change different from a chemical change?

• There is absolutely no difference
• Chemical changes produce a new substance, physical changes stay the same substance
• Chemical changes create and destroy matter, physical changes don't
• Physical changes create and destroy matter, chemical changes dont

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NGSS.MS-PS1-4

If four hydrogen atoms react with two hydrogen atoms, how many atoms will be in the product?

• 6
• 4
• 8
• 2

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NGSS.MS-PS1-5

NGSS.MS-PS1-1

10 g of a solid chemical reacts with a 10 g of a liquid chemical, the reaction bubbles and changes the color of the liquid.  The colored liquid weighs 13 g, what can be concluded?

• The gas produced from the bubbles weighed 5 g
• The bubbles were evidence of 7 g of matter being destroyed
• The gas produced weighed 7 g
• The gas produced weighed 13 g

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NGSS.MS-PS1-5

NGSS.MS-PS1-2

Since gasses weigh nothing, when they are produced in a reaction they do not have to be accounted for.  

• True
• False

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NGSS.MS-PS1-5

All chemical equations create or destroy matter, which is why scientists weigh their reactants so they can see how much was created or destroyed

• True
• False

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NGSS.MS-PS1-5