Collision Theory in Chemistry

What is "collision theory"?

• Reactions only occur when particles collide with sufficient energy

• Collisions occur when particles collide with no energy

• Collisions mean that particles hit each other gently

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NGSS.HS-PS1-5

Why does increasing surface area increase the rate of a reaction?

• Less particles available to collide, so more frequent effective collisions.

• More particles available to collide, so more frequent effective collisions.

• Less particles available to collide, so less frequent effective collisions.

• More particles available to collide, so less frequent effective collisions.

Why does increasing concentration increase the rate of reaction?

• More particles in more space, so more frequent effective collisions.

• More particles in same space, so less frequent effective collisions.

• More particles in same space, so more frequent effective collisions.

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NGSS.HS-PS1-5

Why does increasing gas pressure increase the rate of a reaction?

• Less space for the particles to move, therefore more frequent collisions

• More space for particles to move, so more collisions

How does increasing the surface area of a solid reactant affect the reaction rate?

• It decreases the reaction rate

• It increases the reaction rate

• It has no effect on the reaction rate

• It decreases the energy of collisions

What is meant by collision frequency in the context of collision theory?

• The number of collisions that result in a reaction

• The number of collisions per unit time

• The speed at which particles move

• The energy required for a collision to be effective

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NGSS.HS-PS1-5

In a chemical reaction, if the concentration of reactants is increased, what happens to the reaction rate?

• It decreases

• It increases

• It remains unchanged

• It initially increases, then decreases

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NGSS.HS-PS1-5

Which component of collision theory is represented in the image?

• Correct orientation of molecules

• molecules collide with sufficient energy

• Products become reactants

• Molecules form an activated complex

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NGSS.HS-PS1-5

Why does a higher surface area of a solid reactant increase the reaction rate?

• It increases the density of the reactant

• It decreases the path length for diffusion

• It increases the number of available reactive sites

• It increases the activation energy required for the reaction

Crushing a solid catalyst into finer particles before adding it to a reaction mixture will:

• Decrease the reaction rate.

• Have no effect on the reaction rate.

• Increase the reaction rate.

• Stop the reaction.

Answer explanation

Increasing the surface area of a solid reactant will increase the reaction rate by providing more area for collisions between reactant particles.