SGChem1 Post #4

The main ideas this week in Chemistry continued to mostly be relating to density and measurement. One of the main experiments we did was we measured the density of gas. We began the experiment with a plastic squeeze bottle. We filled it full of water and put it in a basin of red water. We stuck the end of a small tube in the bottom of it. The other side of the tube was connected to a container.

We put a small plastic squeeze bottle with water inside and a cup with an Alka Seltzer in it onto the pan of the balance. Together, it all weighed 72.195 grams. Then, we dropped the cup with the Alka Seltzer into the bottle of water. Gently, we swirled it around. Pretty soon, it started reacting. We waited for approximately 10 minutes as the gas collected in the container. We again measured the mass of everything, which was 71.715 grams. So, puzzlingly, the solution lost .48 grams. We also calculated the volume of the gas, which was 295 mL, which confirmed that the density was .00163. So now we know how to calculate the density of a gas.
One question I still have about this is why did it lose mass? I understand that a chemical reaction probably occurred, causing mass to be lost, but it would interesting to learn exactly what happened.
Another experiment we did in class involving measurement was one where we tried to find the thickness of two pieces of aluminum. We massed the first piece of aluminum and it was 2.62 grams, while the second piece was 2.46. The density of both was 2.7 grams. The surface area of the first piece was 597.36 cm, and the second piece had a surface area of 580.72 cm. So for each piece, we divided the mass by the density and surface area to get the thickness. The thickness of the first piece was .00162 cm, and the second one was .00157 cm.
The important details to the main ideas continue to be units. You have to always be sure of the units you're using. For density, the unit has usually looked something like this: g/mL.
My participation this week was pretty thorough, although in our group, a certain person usually tries to take over everything, and he doesn't really give anyone else a chance, but we're working on that.
I would rate my understanding of what we did this week as a 10/10. We go over everything in class very well and instruction at the beginning of class is very clear and easy to understand.
In the future, I'll work on precision in my calculations, because a lot of the time at our table, the errors we make are calculation errors. It's important to write all our work down, so we don't lose it!
Other than that, the information we learned this week was clear and helpful for further measuring instances.