Questions: What Affects How Fast a Reaction Happens?

Question 1

Why does increasing the temperature generally speed up a chemical reaction?

• A. It adds more reactant particles
• B. It makes particles move faster and collide with more energy
• C. It changes the type of reaction
• D. It removes the products faster

Answer: (B)

Higher temperature gives particles more kinetic energy, so they move faster and collide more often with greater force. More energetic collisions are more likely to break bonds and start the reaction. Temperature does not add particles or change the reaction type.

Question 2

Grinding a solid reactant into a fine powder slows down the reaction because the pieces are smaller.

• T. True
• F. False

Answer: False

Grinding into a powder speeds up the reaction, not slows it down. A fine powder has much more surface area exposed to the other reactant compared to a single large chunk. Since chemical reactions occur at the surface of solids, more surface area means more collisions and a faster reaction.

Question 3

Explain why a campfire burns faster when you blow on it.

Model answer: Blowing increases the supply of oxygen (a reactant) reaching the fire, which increases the concentration of oxygen at the surface of the burning material and speeds up the combustion reaction.

Combustion requires fuel and oxygen. Blowing air on a campfire delivers fresh oxygen to the burning surface more quickly, increasing the rate of collisions between oxygen molecules and the fuel. This is essentially an increase in the local concentration of one reactant, which speeds up the reaction rate.