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How Acids Affect The Rate of Corrosion

By: Maddy and Heather
by

Heather Mackey

on 2 April 2014

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Transcript of How Acids Affect The Rate of Corrosion

How Acids Affect The Rate of Corrosion
Materials
Disposable Gloves
Timer
Test Tube
Thermometer
Steel Wool
Scissors
Ruler
Lemon Juice
Orange Juice
Vinegar
Distilled Water
Four Small Bowls
Thin Towel
Tall Plastic Cup
pH Balance Sheet
Variables
Independent: Level of pH we use (juice)

Dependent: Temperature (Rate of corrosion)
Purpose
We are doing this project to investigate how acids change the rate of corrosion as we compare a model of rainwater and models for acid rain. Normal rain has a pH of about 5.6 and acid rain has a pH of about 5.0 and lower. Rust changes steel into a different material, one that is weaker than the original steel. Rusting is a big problem because so many things people use every day are made out of steel, like cars, trucks, bridges, roofs, holding tanks, machinery, nuts, and bolts. When these objects are unprotected and exposed to water, they begin to rust
Hypothesis
Whatever liquid we choose to use will have a different pH level, which will affect the temperature by how fast it begins to corrode. The lower the pH level, the faster it corrodes. Due to the fact that the liquids we chose to use contained alkaline, a mixture that is also in iron, we believe that this will affect the rate of corrosion, causing it to rust faster.
pH Level Scale
Procedure
1) Wear gloves so hands are not exposed to splinters
2) Cut 9 wool pads (1 inch width)
3)Pour one cup of each acids in small bowls
4) Insert thermometer in rubber stopper
5)Take thermometer with rubber stopper and place it in the test tube
6)Record the temperature of the thermometer in lab notebook
7)Soak the wool pad in acid for 30 sec
8) Repeat step 7 for other acids
9)Take wool pad out of acid and squeeze excess liquid
10)Immediately, remove the thermometer from the test tube and put the soaked wool pad onto the thermometer , below the rubber stopper,
Procedure(2)
11)Place the thermometer probe back into the test tube and press the stopper closed.
12)Wrap the test tube in a thin kitchen towel and place it upright in a plastic cup so you can read the temp
13)Start the timer and record the temperature for the beginning (0), 1, 5, and then 10 min.
14)Stop and reset the timer.
15)Remove the thermometer from the test tube and examine the steel wool. Write down your observations in your lab notebook.
16)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.
17)Repeat steps 11-15 two more times with your first acid, for a total of three trials.
18)Repeat steps 11-16 for the second acid.
19) Repeat steps 1-16 for the third acid
20)Repeat steps 11-16 for the distilled water
Observations
Orange Juice
Observations
Orange Juice
Before : Gray is the original color
After : Reddish Brown after soaked in acid, & the bottom color is a light shade of brown
Shrunk in size
Turned hard
Length Became longer than 1 inch
Width Stayed as 1 inch
Temperature went from 25 degrees Celsius to degrees Celsius.
Vinegar Observations
Vinegar
Before : Gray is the original color
After : Brown after soaked in acid, & the bottom color is a light shade of brown (Same as Orange Juice)
Shrunk into the form of a circle
The hardness caused pieces to fall off (Corrosion)
Length became shorter than 1 inch
Width became longer than 1 inch
Temperature went from 22 degrees Celsius to 25 degrees Celsius.
Distilled Water
Observations
Distilled Water
Before : Gray is the original color
After : Still gray with the exceptions of a few brown spots
Has only a little rust (Corrosion)
Same form before it was put in acid
Not hard, same texture before acid
Length Stayed same
Controlled Variable


Steel wool
Conclusion
The purpose of this project was to find out how different levels of acidity can affect the rate of corrosion. We tested different types of acids with steel wool to see what our results would be and to test our hypothesis. The liquids we used had contained alkaline, which acidic and will speed up the rate of corrosion in the steel. We also did background research on corrosion, and the different types of reasons for corrosion, which helped us draw a hypothesis. As the steel begins to corrode we will see that the color changes and also the temperature of the wool will change, which is why she measured the temperatures in a 15 minute time span.

Lemon Juice
Observations.
Before: Grey is the original color
After: The steel wool began to change in to a relatively brown color.
It had a very fowl smell to it, which we believe to be the steel reacting with the alkaline from the lemon juice.
The temperature went from 21 degrees Celsius to 21 degrees Celsius
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water has a pH very close to 7.
A Definition of "Ph"
pH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution.
We cut the wool into 1inch sections.
The steel wool in the orange juice
The steel wool on the thermometer
The steel wool in the test tube
The test tube wrapped in the dishcloth and put in a cup
All photos are from: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p079.shtml#procedure
We used these photos due to the fact, our own photos that we had taken of our experiment would not load on to our computer.
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