This past week we learned about changes in mass and the exploding can. These main ideas go together because the exploding can was a result of a change in mass. Most of the changes in mass were caused by chemical reactions or human error, but some just stayed the same. One example of a chemical reaction is station 1 regarding Alka-seltzer tablets. We did six different experiments to test changes in mass, but only did one experiment as a whole class on the exploding can.
STATION #1-
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| White board molecule diagram of steel wool being pulled apart |
The first thing we did was mass the pie tin. Then we used the pie tin to mass a piece of steel wool. The next step was to pull the steel wool apart and mass it again. We found that there was no change in mass (0.0 grams). We think there was no change in mass because the molecules spread out not decreased or increased. If the mass had decreased it would probably be due to human error such as failing to keep all of the particles of steel wool in the pie tin while pulling them apart. We used the pie tin to make sure there was no steel wool fallout while pulling the steel wool apart.
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| Steel wool being massed on a balance |
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| Steel wool being massed after being pulled apart |
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| White Board Diagram of of steel wool oxidizing. |
First you mass the pulled apart steel in the pie tin. Then use the tongs to hold the steel wool and put the burner in the pie tin. Light the burner on fire then place the steel wool in the flame. Mass the steel wool in the same pie tin. Before the steel wool was burned it had a mass of 20.21 grams. After the steel wool was burned it had a mass of 21.41 grams. The change in mass was 1.2 grams. Personally I was very surprised by the results. I thought that after burning the steel wool it would loss mass or stay the same, but in fact it increased in mass. I noticed that before the steel wool was burned it was silver but after the steel wool was burned it was an indigo blue color. My table group hypothesized that the added mass after burning the steel wool happened because the steel actually oxidized and created rust on the outside.
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| Steel wool before being burned |
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| Steel wool being burned |
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| Steel wool after being burned |
STATION #3
First you need to find the mass of the vial and the small chip of ice.
Then let the ice melt. To help the ice melt, warm the vial with your hands. After
the ice is melted mass it. The mass before the ice melted was 11.38 grams and the mass
after the ice melted was also 11.38 grams. This means the when ice changes to water its
mass doesn't change. The human error likely to happen is forgetting to zero your
scale. This could result in incorrect conclusions.
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| Ice after being melted |
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| Ice before being melted |
STATION #4
Find the mass of both vials with the solutions inside. Carefully mix
the blue and the clear solutions and shake them up. Then mass the
new mixed solution. The two solutions should become cloudy. The
mass before mixing was 49 grams and the mass after mixing 49 grams. Mixing the
two solutions together does not affect the mass.
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| Mix the clear and blue solutions together |
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| measure the mass of the mixed solution and the empty vial |
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| The mixed cloudy solution |
STATION #5-
Fill vial with water and put sugar in the cap. Mass the vial cap and sugar.
Mix the sugar around softly until it dissolves. When the sugar is completely
dissolved mass the solution.The mass before the vial dissolved was 44.3 grams
and the mass after the vial contents dissolved 43.9 grams The change of mass
was -.3 grams. The negative number could be the cause of human error like
measuring wrong or not zeroing the scale.
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| Water and sugar before being dissolved |
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| Water and sugar solution after being dissolved |
STATION #6-
First fill the vial halfway with water. Then put a fourth of a
Alka-seltzer tablet in the cap of the vial. Them put the vial
and tablet on a scale and mass it out. Put the tablet in the
water and then place the cap on the top. Look what
happens to the tablet. The mass of the water and tablet
before the tablet dissolves was 33.52 grams and the
mass of the solution when it dissolved was 33.45 grams.
The change in mass -0.07 grams. I was surprised by this
result because I thought after dissolving the solution would
increase in mass because of the bubbles but the solution actually
decreased in mass.
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| Vial of water and tablet in cap |
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| Solution after the tablet dissolved |
I think we came to know and understand ideas this week by doing experiments and then sharing our results with the class by making charts and histograms. We also shared our hypotheses by drawing them on our whiteboards and presenting our ideas to the class.
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| Our class table on Station 1 |
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| Our class table for Station 2 |
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| Our class histogram for Station 2 |
One thing I'm still not sure about is how the burned steel wool got more mass than the wool that was not burned. I think I participated very well in the experiments this week and I also think that my table group did an equal amount of participation. From all the concepts we learned this week I rate myself a 9 because I feel pretty confident, but I still have a few questions.
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