Introduction to Chemical Reactions

Multiple Choice

Which of the following is an example of a chemical change?

• water freezes to form ice

• sugar dissolves in water

• gasoline burns in a car engine

• a piece of metal expands when it is heated

Multiple Select

What does it mean for a reaction to be endothermic? Choose 2 of the following.

• When two substances react, the temperature of the mixture decreases.

• When two substances react, the temperature of the mixture increases.

• There is less energy going into the reactant to break the bond than there is energy leaving the product.

• There is more energy going into the reactant to break the bond than there is energy leaving the product.

• The amount of energy entering and leaving is the same.

Multiple Select

What are the 2 ways we say a substance is a solid in reactions?

• (g)

• (s)

• (l)

Multiple Choice

___________________ are the elements/compounds at the beginning of a chemical reaction (on the left).

• Polymers
• Bonds
• Reactants
• Products

Multiple Choice

The Law of Conservation of Mass states

• that matter exists in all states and reacts the same
• that matter can only be changed into new substances by introducing a catalyst
• that matter exists in the same state throughout any chemical change
• that matter cannot be created or destroyed and that the mass of the products must equal the mass of the reactants

Multiple Select

Why are chemical equations always balanced? Select ALL that apply.

• Matter cannot be created.

• Matter cannot be destroyed.

• Matter can only be rearranged/conserved.

• Matter doesn't matter.

Multiple Choice

Your mother used pancake mix, eggs, and milk to make pancakes.  Which of these is the product?

• the pancake mix
• the eggs
• the milk
• the pancakes

Multiple Choice

What are the reactants in the chemical equation pictured?

• CH₄ and CO₂
• CH₄ and O₂
• CO₂ and H₂O
• O₂ and H₂O