Law of Conservation of Matter

Josh is doing an experiment with water. He starts with a plastic cup of water that has a mass of 12 grams. He places the cup in a sealed container and puts it in the freezer overnight. When he takes the container out of the freezer, he notices that the cup has cracked on its sides and the water is now frozen solid. He takes the mass again. Which sentence BEST describes what Josh discovers about the cup of frozen water?

• The mass of the cup of frozen water is 12 grams which means the mass did not change.

• The mass of the cup of frozen water is greater than 12 grams because it changed to a solid.

• The mass of the cup of frozen water is less than 12 grams because the frozen water is lighter than liquid water.

• The mass of the cup of frozen water is greater than 12 grams because the water expanded in the cup when it froze.

Tags

NGSS.MS-PS1-4

Which of the following is a balanced equation for the combustion of ethanol?

• CH3CH2OH + 3O2 → CO2 + 2H2O

• CH3CH2OH + O2 → 2CO2 + 3H2O

• CH3CH2OH + 2O2 → 3CO2 + 2H2O

• CH3CH2OH + 3O2 → 2CO2 + 3H2O

Tags

NGSS.MS-PS1-5

In the balanced form of this equation, what is the coefficient for HCl? __ HCl + Zn → H2 + ZnCl2

• 4

• 2

• 3

• 1

Tags

NGSS.MS-PS1-5

An unbalanced chemical equation is shown below. __Pb(NO₃)₂ + __K₂CrO₄ → __PbCrO₄ + __KNO₃ Which coefficients are needed to balance this equation?

• 2, 4, 4, 6

• 2, 4, 4, 3

• 1, 1, 1, 2

• 1, 6, 6, 2

Tags

NGSS.MS-PS1-5

Hydrazine, N₂H₄, and dinitrogen tetroxide, N₂O₄, react to form gaseous nitrogen and water. Which of these represents a properly balanced equation for this reaction?

• 2N₂H₄ + N₂O₄ → 3N₂ + 4H₂O

• 2N₂H₄ + N₂O₄ → 2N₂ + 4H₂O

• N₂H₄ + N₂O₄ → N₂ + H₂O

• 2N₂H₄ + 3N₂O₄ → 5N₂ + 6H₂O

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

When this equation is balanced, what is the coefficient for potassium carbonate? 6KOH + 3CO₂ → __K₂CO₃ + 3H₂O

• 3

• 2

• 6

• 9

Tags

NGSS.MS-PS1-5

Justin Bleeber is a lazy young man and decides to burn a pile of leaves instead of bagging it. The pile of leaves weighed three pounds before being burned. After the leaves are burned the leftover ash weighs half a pound. What happened to the rest of the mass of the leaves?

• It was destroyed.

• It soaked into the ground.

• It compacted into the ash.

• It was turned into smoke and gas.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

20g of sugar is stirred into a beaker containing 100 g of water. After the sugar has completely dissolved, the solution is put on the scale. What is the mass of the solution?

• 120g

• 80g

• 100 g

• 20 g

Tags

NGSS.MS-PS1-5

A mixture of baking soda is prepared in water. The mass of this mixture is 225g. The original mass of baking soda was 50g. What is the original mass of water to which the baking soda was added?

• 50g

• 175g

• 225g

• 275g

Scot has a 50 g sample of sandstone. The sandstone is formed by sedimentation, compaction, and cementation of 50 g of sand particles. Based on this information, what can Scot conclude?

• Mass is conserved in the rock cycle.

• The structure of sand remains the same.

• The sand retains its properties within sandstone.

• The volume of the parts is conserved in the rock cycle.

Tags

NGSS.MS-ESS2-2