KS3 CHEMISTRY Flashcards
(20 cards)
What is rate of reaction?
The speed at which a reactants are turned into products
Why can there be different units for measuring rate of reaction?
Different units can be used depending on what is being measured. E.g. gas may measured using cm^3/s while change in mass may be measured using g/min
List some factors that can affect the rate of a reaction:
- Temperature
- Concentration/Pressure (for gasses)
- Surface area
- Presence of a catalyst
Explain using collision theory how temperature affects the rate of reaction:
A higher temperature increases energy of particles, making them faster. This leads to more frequent collisions, increasing the rate of reaction.
Explain using collision theory how pressure affects the rate of reaction:
Increasing the concentration/pressure for gasses means that there is more particles in the same amount of space. This leads to more frequent collisions, increasing the rate of reaction.
Explain using collision theory how surface area affects the rate of reaction:
By increasing the surface area it exposes more particles to the reactant. This results in more frequent collisions, increasing the rate of reaction
Explain using collision theory how a catalyst affects the rate of reaction:
A catalyst lowers the activation energy needed for a reaction. This creates more collisions, increasing the rate of reaction.
Describe how temperature affects the rate of reaction:
Increasing the temperature makes particles more faster, causing more frequent collisions. This increases the rate of reaction.
How do you calculate the rate of a reaction from a graph?
Reactant used or product formed --------------------------------- Rate of reaction × Time
How do you increase the surface area of a solid?
Break it up into smaller pieces or turn it into a powder
How does surface area affect the rate of reaction?
A larger surface area increases the number of exposed particles. This leads to more frequent collisions, increasing the rate of reaction.
How do you calculate surface area to volume ratio?
Surface area ÷ volume
How does changing concentration affect the rate of reaction?
A higher concentration means more particles are present, leading to more collisions and a faster rate of reaction
How does changing pressure affect gaseous reactants?
Increasing pressure compresses gas particles. This makes collisions more frequent and increases the rate of reaction.
What is activation energy?
Activation energy is the minimum amount of energy needed for a reaction to occur
What is a catalyst?
A catalyst is a substance that increases the rate of a reaction (it does not get used up)
How does a catalyst affect the rate of reaction?
It lowers the activation energy, so more collisions occur during a reaction.
How do you interpret a graph involving rates of reaction?
A steeper gradient shows a faster reaction. A flat line means the reaction has stopped.
How do you identify independent, dependent, and control variables from a graph?
Independent veriables are on the x-axis, dependent are on the y-axis, and control variables are kept the same throughout the experiment.
How do you use a tangent to calculate the rate at a specific time?
1) Find the point on the curve where you want the rate.
2) Draw a tangent line - a straight line that just touches the curve at that point.
3) Pick two points on the tangent line (not the curve).
4) Use this formula to find the gradient (rate):
