Materials:
Disposable Gloves
Timer
Test tubes
Thermometer
Steel Wool
Scissors
Ruler
Lemon Juice
Orange Juice
Vinegar
Distilled Water
Four Small Bowls
Thin Towel
Tall plastic cup Graph Paper
Procedure:
Before beginning your experiment, make sure that the distilled water has been opened and exposed to the air for at least a few hours. This will allow it to absorb some carbon dioxide from the atmosphere and lower its pH from a level of about 7 to about 5.8. The distilled water will act as a model for "normal" rainwater, which has a pH of about 5.6.
The three acids (Orange juice, Lemon juice, and Vinegar) you have chosen will act as three different models for acid rain, each with a different pH level.
Make sure all your materials are at room …show more content…
temperature.
Data Table
Time (min)
Trial 1 Temperature (°F)
Trial 2 Temperature (°F)
Trial 3 Temperature (°F)
Trial 4
Temperat ure (°F)
Trial 5 Temperat ure (°F)
Average Temperat ure (°F)
1
2
3
4
5
Put on your disposable gloves to help prevent you from getting splinters from the steel wool.
Using the ruler, measure 1 inch (in.) along the length of a steel wool pad. Cut across the width of the pad with the scissors at the 1-in. mark. Set the cut strip aside. Continue through the width of the pad, at 1-in. intervals, until it is used up. Repeat step 2 for two or more pads, or until you have a total of fifteen 1-in. strips of steel wool. 3. Pour approximately 1 cup of your first acid into a small bowl. 4. Pour approximately 1 cup of your second acid into a second small bowl. 5. Pour approximately 1 cup of your third acid into a third small bowl. 6. Pour approximately 1 cup of the distilled water that has been exposed to the air for at least a few hours into a fourth small bowl.
Testing Your Rain Models
Have your thin kitchen towel and plastic cup nearby.
Thread the rubber stopper onto the thermometer probe.
Place the rubber stopper, with its attached probe, inside the test tube. Record the temperature of the thermometer in your lab notebook. This will be your temperature at "time equals
zero."
Soak a strip of steel wool in the bowl of your first acid for 30 seconds (sec). It might float to the top of the liquid, so hold it under the surface with your fingers.
Remove the steel wool from the first small bowl and squeeze out the excess liquid for a couple of seconds over a sink.
Immediately, remove the thermometer probe from the test tube and thread the soaked steel onto the thermometer probe, below the rubber stopper, as shown below. Twisting the probe as you thread it through the steel wool may help it go on more easily.
Place the thermometer probe back into the test tube and press the stopper closed.
Wrap the test tube in a thin kitchen towel and place it upright in a plastic cup so you can read the gauge. The towel and cup will help retain any generated heat. Work quickly to set this up, because the reactions are already taking place.
Start the timer and record the temperature every minute for 10 min., and then once more 5 min. Later.
Stop and reset the timer.
Remove the probe from the test tube and examine the steel wool. Write down your observations in your lab notebook. Use the ruler to measure the greatest length of rusting observed.
Throw away the steel wool and wash and dry the test tube. Rinse and dry the thermometer probe. Allow the test tube and probe to come to room temperature before doing any more trials.
Repeat steps 1–12 two more times with your first acid, for a total of three trials.
Repeat steps 1–13 for the second acid.
Repeat steps 1-13 for the third acid.
Repeat steps 1–13 for the distilled water.
Analyzing Your Results
For each time listed in each data table, calculate and record the average temperature.
Using the table below, determine the pH of the liquids you tested and write them down in your lab notebook.
For each data table, make a line graph showing the time on the x-axis and the average temperature on the y-axis.
pH Table for Liquids
Liquid
Approximate pH Level
Lemon juice
2.2
Vinegar
3.0
Lowest acid rain recorded in the Great Smoky Mountains National Park (1981)
3.6
Orange juice
3.7
Tomato juice
4.1
Average rain in the eastern United States today
4.5
"Normal" rain
5.6
Distilled water, exposed to air
5.8
Distilled water, fresh, not exposed to air
7.0
Variables:
Independent Variable: Acids (Orange juice, Lemon juice, and Vinegar)
Dependent Variable: Temperature (Rate of corrosion)
Constant Variable: Steel wool