Law of the Conservation of mass

Which is best represented by the equation?2Mg + O2 2MgO

• Law of Conservation of Energy

• Law of Conservation of Mass

• Law of Superposition

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

How does a balanced chemical equation satisfy the Law of Conservation of Mass?

• During a chemical reaction, the total amount of matter stays the same.

• During a chemical reaction, matter is destroyed.

• During a chemical reaction, one or more new substances are formed

• During a chemical reaction, the total number of atoms increases.

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NGSS.MS-PS1-5

If a chemical reaction such as photosynthesis begins with 8 atoms of carbon (C), how many atoms of carbon (C) should be in the products?

• 12

• 8

• 6

• 2

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NGSS.MS-PS1-5

Which best explains why the total mass of the product(s) would be less than the total weight of the reactant(s) after a chemical reaction?

• A physical change occurred.

• Atoms involved in the reaction lost mass.

• Precipitates were created in the new solution.

• Gases were released into the atmosphere.

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NGSS.MS-PS1-5

The equation below shows a reaction between sodium (Na) and water (H2O).

2Na (s) + H2O (l) → 2NaOH (aq) + H2 (g)

Which best explains why the equation is not balanced?

• There is too much sodium in the reactants.

• There is not enough water in the reactants.

• There is too much hydrogen gas in the products.

• There is not enough sodium hydroxide in the products.

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NGSS.MS-PS1-5

Following the lab procedures below in completing an experiment.

1. Place samples of iron filings and sulfur into a test tube.

2. Cover the test tube with a rubber sheet and seal it.

3. Measure and record the mass of the test tube and contents.

4. Heat the test tube until the contents glow red.

5. Allow the test tube to cool.

6. After cooling, remeasure and record the mass of the test tube and contents.

Which best describes the conclusion?

• A change in mass occurred after heating.

• No change in mass occurred after heating.

• A physical change occurred, producing new products.

• A chemical change occurred, producing new reactants.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which best explains how the chemical reaction shown below follows the law of conservation of mass?

2H2 + O2 → 2H2O

• The hydrogen and oxygen molecules combine to form water.

• Hydrogen and oxygen are held together by strong chemical bonds.

• There are hydrogen and oxygen atoms on both sides of the equation.

• The same number of hydrogen and oxygen atoms are on both sides of the equation.

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NGSS.MS-PS1-5

Max recorded the notes below as he completed an experiment in science class.

20 grams of a solute was added to 100 grams of a liquid substance. The solute completely dissolved. The total mass of the resulting solution was 120 grams after the experiment was complete.

Which best explains how the law of conservation of mass was demonstrated in the experiment?

• The solute completely dissolved in the liquid.

• The liquid was chemically changed by the addition of the solute.

• Some of the mass of the solute was lost during the experiment.

• The mass of the resulting solution was equal to the mass of the solute and liquid.

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NGSS.MS-PS1-5

When chemicals react in a closed container, which must be true?

• The mass both before and after the reaction is the same.

• The mass both before and after the reaction is variable.

• The same number of compounds is present both before and after the reaction.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Substance A has a mass of 7 grams. When substance A was mixed with substance B, a new substance was formed. Which statement best describes the Law of Conservation of Mass?

• The mass of substance B is equal to the mass of the product.

• The mass of the product is equal to the mass of the reactants.

• The mass of the product is less than the mass of the reactants.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5