Law of Conservation of Mass

Fill in the blank:
The law of conservation of mass states that matter cannot be created nor __________________.

• destroyed
• rearranged
• transferred
• changed

Tags

NGSS.MS-PS1-5

In a closed system, a chemical reaction takes place.  The mass of the reactants in the beginning of the reaction is 25g.  What does the mass have to be in the end of the reaction in order to follow the law of conservation of mass?

• 25g
• You can't tell with the given information.
• 30g
• 15g

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

The following chemical reaction occurs:
2S + 3O₂ -> 2SO_{3
How many atoms of oxygen are there in the reactant?}

• 2 atoms of oxygen
• 3 atoms of oxygen
• 6 atoms of oxygen
• 1 atom of oxygen

Tags

NGSS.MS-PS1-1

There are two reactants in a chemical equation, and one product.  The mass of the product is 30g.  The mass of the first reactant is 17g.  What must the mass of the second reactant be, if the equation is to follow the law of conservation of mass?

• 47g
• 13g
• 23g 
• You cant tell with the given information

Tags

NGSS.MS-PS1-5

Students react baking soda & vinegar.
Which of the following would provide the evidence that the number of atoms present before a chemical reaction is equal to the number of atoms present after the chemical reaction?

• The mass of the plastic bag, baking soda, and vinegar before the reaction was equal to the mass after the reaction.
• Bubbles were produced during the reaction, which meant that a gas was being produced.
• The plastic bag did not change in any way, indicating that it was not involved in the reaction.
• The mass of the baking soda was exactly equal to the mass of the vinegar used to create the chemical reaction.

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

How many IRON atoms are in this chemical formula?

• 4 iron atoms

• 2 iron atoms

• 8 iron atoms

• 3 iron atoms

How many chlorine atoms are in 3MgCl₂?

• 6

• 5

• 1

• 2

Tags

NGSS.MS-PS1-1

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

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.