Review.CC.Balance.Law of Conserveration of Mass

In chemical reactions, what does the principle of conservation of mass mean?

• Matter is not created or destroyed.
• The total mass of the reactants is greater than the total mass of the products.
• The total mass of the reactants is less than the total mass of the products.
• Matter is not changed.
  

Chemical reactions occur when _________ are broken and new bonds are formed.

• mixtures
• osteoclasts
• physical bonds
• chemical bonds

At the end of chemical reactions, what is the total mass of the reactants compared to the total mass of the products?

• the product is doubled
• the product is half the mass of the reactants
• the mass is the same
• the mass changes depending on the reaction

starting material in a chemical reaction

• subscript

• coeffient

• reactants

What coefficient is needed to balance the equation?

N₂ + _H₂ -> 2NH₃

• 2

• 6

• 1

• 3

People get energy from the food that they eat and transform that energy as they move. Which energy transformations occur as a student rapidly rubs the palms of his hands together?

• mechanical to thermal to electrical
• chemical to mechanical to thermal
• mechanical to chemical to sound
• chemical to sound to electrical

How many oxygen atoms are present in the following? 
4Ca(OH)₂

• 4
• 6
• 8
• 1

During a lab experiment, a scientist numbers three beakers. Next, she pours 150 mL of  liquid into each beaker. Each liquid is different.Then, the scientist adds 5 g of white solid baking soda (NaHCO₃) to each beaker and stirs. She observes the results.
In which of the beakers does the scientist observe clear evidence of a chemical reaction?

• beaker 1 only
• beaker 2 only
• beaker 3 only
• beakers 1,2, and 3

Does the image represent the Law of Conservation of

• yes

• no

Balance this equation.
_Mg + _Cl₂ --> _MgCl₂

• 1, 2,1
• already balanced
• 2,1,1
• 1,1,2