7.4 Rates of Reaction Flashcards
How can you measure the rate of a reaction?
The rate at which a reactant is used up, The rate at which a product is formed
Name 2 factors which can affect the rate of a reaction.
Temperature/pressure/concentration/SA/ catalysts
What has to happen to particles for a reaction to occur?
Collide with enough energy
Define the term activation energy.
The amount of energy required for them to react
How can you measure the rate of a reaction when a solid dissolves?
Mass of substance used up
How can you measure the rate of a reaction when a gas is given off?
Volume of gas given off
What are the units for rate of reaction?
g/s orcm3/s or mol/s
Which variable is plotted on the x-axis of a rate graph?
Independent / Time
What variable can be found on the y-axis of a rate graph?
Dependent / Amount of product formed or amount of reactant used
How can you calculate the average rate across a period of time?
Change in Y / Change in X
What is a tangent?
A tangent is a straight line drawn on a curve
What information does a tangent provide?
The rate of reaction at a specific point
What does it mean when the curve on a rate graph gets steeper?
The rate of reaction is increasing
What does it mean when the curve on a rate graph gets shallower?
The rate of reaction is decreasing
How can you tell that a reaction has finished from a rate graph?
The line becomes constant/ horizontal
What is the rate of reaction?
The rate of a reaction is how quickly the products are being made
Name 2 factors that affect the rate of a reaction.
Temperature/concentration/SA/pressure
What is the scientific term for movement energy?
Kinetic Energy
When temperature is increased what energy store increases in the particles?
Thermal Energy
What does the term activation energy mean?
The minimum amount of energy that the reactant particles must collide with to cause the reaction to occur
How does increasing temperature increase the rate of a reaction?
The particles have more kinetic energy
How does increasing pressure increase the rate of a reaction?
The particles are closer together and so more likely to collide
How does increasing surface area increase the rate of a reaction?
There are more reactants available to react
Define the term activation energy.
The amount of energy needed for a reaction to occur
What does a reaction profile show?
The energy changes during a chemical reaction
In an endothermic reaction- which has higher energy, reactants or products?
Products
In an exothermic reaction- which has higher energy, reactants or products?
Reactants
Is energy absorbed or released when new bonds are made?
Released
Is energy absorbed or released when bonds are broken?
Absorbed
What decides if a reaction is exothermic or endothermic?
The difference in energy needed to break bonds and the energy released when new bonds form
What equipment could you use to tell if a reaction is exothermic or endothermic?
Thermometer
What is a catalyst?
A substance which increases the rate of a chemical reaction without being used up itself.
How does a catalyst increase the rate of a reaction?
Provides an alternate pathway for the reaction to occur
What is an enzyme?
A biological catalyst
What are enzymes made from?
Proteins
Why is the shape of the active site of an enzyme important?
Complimentary to the substrate
What is the ‘lock and key’ model?
The enzyme and substrate have specific complementary shapes
Name 2 factors that can affect the effectiveness of an enzyme.
Temperature and pH
What are conditions in the human stomach like?
Acidic
What is a reversible reaction?
A reaction that can produce products, but the products can also react to create the reactants
What is a dynamic equilibrium?
The forward and backward reaction occur at the same rate?
HT: In which direction does an equiliubrium shift if temperature is increased?
In the endothermic direction
HT: In which direction does an equiliubrium shift if temperature is decreased?
In the exothermic direction
HT: In which direction does an equiliubrium shift if pressure is increased?
In the direction of fewer particles
HT: In which direction does an equiliubrium shift if pressure is decreased?
In the direction of more particles
HT: In which direction does an equiliubrium shift if concentration of reactants is increased?
In the direction of the products
HT: In which direction does an equiliubrium shift if concentration of products is increased?
In the direction of the reactants
What colour change would you expect to see when iodine is added to starch?
From brown to blue - black
Why does increasing surface area increase the rate of a chemical reaction?
It increases the available particles for the reaction
Why does increasing temperature increase the rate of a chemical reaction?
It increases the energy of the particles
What is a tangent?
A straight line drawn on a curve
How does a catalyst increase the rate of reaction?
Gives the reaction an alternate pathway and increases the rate.
What term matches this definition? Energy required to start a reaction
Activation energy
What term matches this definition? Part of an enzyme where the substrate becomes a product
Active site
What term matches this definition? The chemical energy stored in the bonds between atoms
Bond energy
What term matches this definition? Substance which speeds up a reaction
Catalyst
What term matches this definition? Particles must collide to cause a reaction
Collision theory
What term matches this definition? Forward and backwards reactions occur at the same rate
Dynamic equilibrium
What term matches this definition? Reaction which absorbs energy from the surroundings
Endothermic
What term matches this definition? A biological catalyst
Enzyme
What term matches this definition? Reaction which releases energy to the surroundings
Exothermic
HT: What term matches this definition? Dynamic equilibrium can shifts due to external factors
Le Chatelier’s principle
What term matches this definition? Model which explains how enzymes are specific to their substrate
Lock and key model
What term matches this definition? Diagram to show the energy changes during a reaction
Reaction profile
What term matches this definition? Reaction where products can react to produce the reactants
Reversible reaction
What term matches this definition? The substance an enzyme works on
Substrate
What term matches this definition? The ratio of surface area to volume
Surface area:volume
