Chemistry Term 3 26 SCI

What is collision theory and what are the three requirements for a successful collision?

chemical reaction can only occur when.

1. Particles collide.

2. sufficient energy, at least activation energy.

3. correct orientation.

If not, particles collide but do not react.

Activation Energy

minimum energy required for a successful collision and reaction to occur.

How does temperature affect the rate of reaction? Explain using collision theory

Increasing temp increases reaction bc:

• Particles gain energy, move faster.

• collide more frequently.

• more collisions have enough energy to overcome activation energy.

• more successful collisions in given time.

Decreasing temp- opposite

How does concentration affect the rate of reaction? Explain using collision theory.

increases rate of reaction bc more reactant particles in same volume.

• more likely to collide,

• more frequent successful collisions

diluting solution- fewer particles, fewer collisions, slower

How does surface area affect the rate of reaction? Explain using collision theory

more sa increases rate of reaction bc more reactant particles exposed, available to collide with other reactant.

Breaking solid into smaller piece/ powder increases sa

How does agitation affect the rate of reaction? Explain using collision theory.

stirring/ mixing reactants.

increases reaction rate bc

• Keeps reactants in contact.

• Removes build-up of products around reactants.

• more frequent and successful reactant collisions

What is a catalyst and how does it affect reaction rate? Examples

increases reaction rate- providing a pathway requiring less activation energy, meaning more particles can have successful collisions.

can be reused. Enzymes are biological catalysts

• Amylase → in saliva breaks down starch into simple sugars.

• Enzymes in washing powders → break down substances during cleaning.

What are the main methods of changing the rate of a reaction?

• Temperature

• Concentration

• Surface area

• Agitation

• Catalysts

• Pressure — for gases

How does reaction rate change as a reaction proceeds?

generally fastest at beginning and becomes slower

As reactants used up:

• fewer reactant particles.

• Collisions less frequent.

• fewer successful collisions.

• reaction rate decreases.

reaction complete, rate approx zero.

What are the products of acid + metal

Acid + metal → metal salt + hydrogen

Acid + metal oxide → metal salt + water

Acid + metal hydroxide → metal salt + water

Acid + metal carbonate → metal salt + water + carbon dioxide

Acid + metal hydrogen-carbonate → metal salt + water + carbon dioxide

Reaction Rate

how fast or slow a chemical reaction proceeds.

fast- high reaction rate, slow- low

What is Newton's Second Law?

Force = mass (kg) x acceleration (m/s²)