Reflection Journal 2

This past week in Chemisty, we did a lot of experiments that had to do with gas and air pressure.  The first lab we did was using the straws to fill the pillow (garbage bag) with air, to lift a person up.  I thought this was a really good representation of what pressure really is and what it can do.  We learned that when we blew air in, the particles in the pillow collided with the sides of the bag, expanded, and as a result, filled the bag enough to lift a person off of the ground.  Another experiment we did was showing how the Petri dish filled with water can stick to the top of a glass container if there were no air particles in it.  Initially, I thought the dish would fall off and spray water everywhere, but once Mr. Grosshuesch explained how there were no air particles in the dish once he stuck it to the glass, it made sense.  I learned that all of the air particles escape upon pressing it to the glass, leaving only the water in the glass.  The same explanation works for a window cling-on; all of the air particles escape once you press it on the surface.  In class, we were also shown how mercury has a higher density than water by putting a certain amount of it in a very tall glass tube.  I was a little confused about this whole thing. What I understood was that, when air was put into the tube along with the mercury, the amount of Hg went down, and the air particles traveled to the top of the tube.  Along with this experiment, we watched a video on “the world’s longest straw”.  What the guys in the video were trying to say was that, the amount of air pressure we force upon the straw, can only go so far, before we cannot possibly get any drink from the straw to our mouths.  The guys determined that the farthest height was 10.5 meters.  I’m still a little confused about this concept; if that was what the video was about or not.  The last lab we did was with the syringes.  Using the little computers, we had to plug in the volume of the syringe for each interval.  Then, we had to press down on the piston using a certain amount of pressure.  In the beginning, I thought that the relationship between the pressure and volume would be direct- making a straight line going down from left to right.  However, after we conducted the experiment, I noticed that the line wasn’t straight and that the data was indirect.  So instead of going straight, it had a curve in it.

During the course of last week, I learned more about gas and air pressure.  Specifically, about their indirect relationship- if one goes up, the other goes down.  I’m still a little confused about the mercury experiment and how exactly the mercury escaped while the air got in?  I thought my participation was good; I helped my group members with each white board activity and talked a lot.  At this point, I need to work more on my understanding on tougher concepts and to seek help when I need it.