Speed It Up with
Temperature!
Name: __________________________________
Date:
__________________________________
Student worksheet
Directions: Answer the questions below in preparation for the experiment.
1. Pre-Experiment
a. In your own words, explain how you will monitor the chemical reaction over time. How
will you know when the reaction is done?
b. What are the independent and dependent variables in your experiment? Remember, an
independent variable is what you change; dependent variables are what you measure.
c. Write down your hypothesis about how temperature will affect the bleaching reaction.
Write 1–3 sentences explaining why this is your hypothesis.
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Speed It Up with
Temperature!—Page 2
Name: __________________________________
Directions: Follow the steps below to conduct your experiment.
2. Experiment
Experiment 1: Ice Water
a. Prepare the dye solution for the first experiment using 500 mL of ice water and 8 drops
of the yellow food dye. Mix the solution.
b. Fill the beaker with 150 mL of dye solution. Measure and record the temperature of
your solution in the data table given below. Average the temperature for each
experimental condition.
c. Open the Science Journal app on the phone and start a new experiment. Remember to
give each experiment a clear name. Select the light sensor and switch to the graph
mode.
d. Set up your experiment as shown in the diagram. Make sure the flashlight in front of the
beaker shines through the dye solution directly onto the light sensor of the phone.
Note that the light sensor reading will be dependent on the position of the flashlight with
respect to the phone. You might want to try different positions to get the highest lux
readings. Do not move the flashlight or the phone while you are recording data.
e. Suck up 2 mL of the pre-prepared 1:20 diluted bleach solution with the pipette and hold
it above the dye solution.
f. Confirm that the light intensity readings are stable. Then, press the record button in the
Science Journal app and, immediately after, add all of the bleach to the cup. Use the
pipette to stir the solution and keep stirring throughout the experiment. You will observe
the food color fade in the reaction mixture while the app will record the color change
over time with the light sensor.
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Speed It Up with
Temperature!—Page 3
Name: __________________________________
Directions: Continue following the steps below to conduct your experiment.
g. While stirring, the lux readings will temporarily drop every time the pipette passes in
between the sensor and the flashlight, as shown in the graph below. This will not affect
the results of the experiment.
h. Press the record button again to stop recording once the maximum lux readings level
off and are stable for more than 30 seconds. The light intensity should stabilize right
when the color fully disappears from the solution.
i. Repeat the ice water experiment for two more trials with the same temperature,
following steps b.–h. again. Make sure to give each experiment and trial a clear name.
The initial light intensity does not have to be exactly the same for each experiment. The
absolute values on the y-axis do not really matter, as you only care about the time
when the lux readings level off.
Experiment 2: Room Temperature Water
j. Once all trials for the first temperature have been completed, repeat steps a.–i. using
room temperature water for the new dye solution. Make sure the difference between
each temperature is at least 10°C.
Experiment 3: Hot Water
k. Once all trials for the room temperature experiment have been completed, repeat steps
a.–i. using hot water for the new dye solution. Make sure the difference between each
temperature is at least 10°C.
3. Record and Analyze Your Data
a. Determine the reaction time from each of the
graphs for your experiments and trials. To do
this, find the endpoint of each reaction, or the
time at which the light intensity first leveled off,
in each graph. Dragging the cursor along the
x-axis will give time and lux values for each
individual time point, as shown in the graph
(right).
In the graph shown here, the reaction is
completed at 20.8 seconds, which is when the
maximum lux value stops changing.
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Speed It Up with
Temperature!—Page 4
Name: __________________________________
Directions: Follow the steps below to record your data.
b. Record your results in the data tables below and calculate the average reaction times
from all your trials for each temperature average.
Experiment 1: Ice Water
Trial
Temperature [°C]
Reaction Time [s]
Reaction Rate [M/s]
1
2
3
Average
Experiment 2: Room Temperature Water
Trial
Temperature [°C]
Reaction Time [s]
Reaction Rate [M/s]
1
2
3
Average
Experiment 3: Hot Water
Trial
1
2
3
Average
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Temperature [°C]
Reaction Time [s]
Reaction Rate [M/s]
Speed It Up with
Temperature!—Page 5
Name: __________________________________
Directions: Continue following the steps below to analyze your data.
c. Convert the reaction time for each temperature into an average reaction rate using the
equation given below. Record the results in your data table and again calculate the
average from all your trials for each experimental temperature.
Change in dye conc. [M] = Final dye conc. [M] – Initial dye conc. [M]

Final conc. of dye [M] = 0 M

Initial dye conc. [M] = 0.0005 M
Change in time [s] = Final time [s] – Initial time [s]

Final time [s] = Time at end of reaction [s]

Initial time [s] = 0 s
d. Which temperature resulted in the fastest reaction rate? Which one resulted in the
slowest?
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Speed It Up with
Temperature!—Page 6
Name: __________________________________
Directions: Answer the questions below.
4. Reflection
a. Explain, in your own words, what happens in the reaction solution on a molecular level
when you change the reaction temperature.
b. Considering your answer in question 4.a, explain why the reaction rate is temperaturedependent.
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