Simulation: Investigating Reaction Rates
Background
In this lesson you will investigate four factors or variables that can affect the rate of a chemical
reaction.
Go to: teachchemistry.org/reaction-rates
Investigation
1. Run the reaction.
2. Describe the reaction that occurs.
During the 5 second reaction, the reactants, shown as blue and red spheres, react
with each other to form product, shown as purple. This implies a synthesis reaction.
3. Provide the general equation for the reaction.
A+BC
4. Below is the graph produced by the “control” experiment.
a) Which substance from your equation in question #3 is being shown on the graph?
The graph shows the amount of substance C (the product) formed over time.
b) Describe the importance of the “control” or “controlled reaction”.
Running a controlled reaction allows for a comparison of the controlled
measurement of reaction rate with the measurements of reaction rate when the
variables are changed. A control helps guarantee that the changes noted in the
experimental reactions are from the changes in the introduced variables.
c)
The slope of the line is equivalent to the rate of the chemical reaction. Provide the
equation for calculating reaction rate using the two variables from the graph.
rate = change in amount of product C
change in time
5. The simulation allows you to manipulate several variables or factors that can change or affect
the rate of the reaction. These altered reaction rates can be compared against the controlled
reaction. List the four variables that will be examined.
Temperature
Concentration
Surface area
Addition of a catalyst
Analysis
7. For each graph, based on the slope of the line, how can you tell if the reaction is occurring
more quickly or more slowly than the controlled reaction?
A steeper slope (steeper line) means that the product is formed at a faster rate (more
quickly) than it was in the controlled reaction.
A less steep slope (less steep line) means that the product is formed at a slower rate
(more slowly) than it was in the controlled reaction.
8. What variable changes caused the reaction rate to increase (caused the product to form more
quickly)?
Increased temperature
Increased concentration
Increased surface area
Addition of a catalyst
9. What variable changes caused the reaction rate to decrease (caused the product to form
more slowly)?
Decreased temperature
Decreased concentration
Decreased surface area
10.Describe each of the following variables in terms of what is changing about the particles of
the reacting substances when the variables are changed:
(In other words, when each factor is increased or decreased, what difference is seen in terms
of the reacting particles?)
Temperature-
Temperature change affects the kinetic energy of the particles., and therefore their
speed/velocity. At higher temperatures particles have higher average kinetic
energies, and collide more frequently (and with greater intensity).
Concentration-
Changing the concentration changes the amount of particles present in a given
volume. Increasing the concentration of the reactants increases the number of
collisions between them.
Surface Area-
Changing the surface area changes the spacing of the particles and the exposure of
the reactants to each other. An increase in surface area provides more opportunity
for reactants to interact, meaning more collisions between them.
11.Define “catalyst”:
A catalyst is a substance that increases the rate of a reaction, but is not consumed by
the reaction. (The catalyst causes the reaction to happen faster while it itself, is
unchanged chemically, and therefore, does not appear in the overall reaction
equation.)