Ch. 3 Chemical Reactions Review

What is the main difference between a physical change and a chemical change?

• A chemical change forms a new substance

• A physical change creates energy

• A chemical change involves state changes only

• A physical change produces heat

What happens to atoms during a chemical reaction?

• Atoms are destroyed

• Atoms rearrange to form new substances

• Atoms disappear into gas

• New atoms are created

Which of the following indicates that a chemical reaction has occurred?

• Change in color or formation of gas

• Boiling of water

• Melting of ice

• Breaking of glass

What is a synthesis reaction?

• A reaction that breaks substances into simpler products

• A reaction that absorbs energy

• A reaction that combines two or more substances into one product

Which of the following is a decomposition reaction?

• H₂O + CO₂ → H₂CO₃

• H₂CO₃ → H₂O + CO₂

• 2 H₂ + O₂ → 2 H₂O

• C + O₂ → CO₂

What is always involved in a combustion reaction?

• Oxygen

• Nitrogen

• Carbon dioxide

• Water

What are four factors that affect the rate of a chemical reaction?

• Volume, shape, density, and mass

• Concentration, surface area, temperature, and catalyst

• Pressure, temperature, mass, and density

• Catalyst, solution, melting point, and freezing point

How does a catalyst affect a chemical reaction?

• It increases the activation energy required

• It speeds up the reaction without

Which of the following statements describes the law of conservation of mass?

• The mass of the products is greater than the mass of the reactants

• Mass cannot be created or destroyed during a chemical reaction

• The mass of reactants increases after a reaction

• Mass is always lost in a chemical reaction

Which of the following equations shows a correctly balanced reaction?

• H₂ + O₂ → H₂O

• 2 H₂ + O₂ → 2 H₂O

• 2 H₂ + 2 O₂ → H₂O₂

• 4 H₂ + 2 O₂ → 4 H₂O