5.4 Lecture

5.4 Rates of Change

Pages 169 - 174

Goal 1

Describe the 5 factors that affect reaction rates

Collision Theory (memorize this)

“chemical reactions can only occur if

particles collide with enough energy to

result in activation”

• 1. Temperature– High temp = faster reaction rate– Low temp = slower reaction rate– Why?.... collisions

• 2. Surface Area– More exposed surface area = faster– Less exposed surface area = slower– Why?.... collisions– Diet coke and Mentos ??

• 3. Concentrations– Higher concentration = faster – Lower concentration = slower– Why?.... collisions

• 4. Pressure– High pressure = faster – Low pressure = slower– Why?.... collisions

• 5. Mass– Less mass = faster– More mass = slower– Why?.... collisions

• Summary of 5 factors

–1. Temperature

–2. Surface Area

–3. Concentration

–4. Pressure

–5. Mass

Goal 2

Explain the affect a catalyst has on the rate of a reaction

• Catalysts change the rate of a reaction

– Catalysts themselves do not change or get used up

– Slows a reaction = Inhibitor

• Enzyme = biological catalyst

– Substrate = substance / reactants that are affected by enzyme

• Enzymes shape specific like a “lock & key”

– The enzyme “catalase” only breaks down hydrogen peroxide

Hydrogen peroxide water + oxygen

Goal 3

Explain chemical equilibrium

• Reversible reactions– SOME reactions are reversible– reversible reactions shown by

CaCO3

CaO + CO2

• Reversible reactions in Equilibrium system– will be in equilibrium– Equal amounts going both ways

CaCO3

CaO + CO2