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.  

Reflection Journal #1

During the past 2 weeks of class, we did several experiments to get an idea of what we are in store for this year in chemistry. 

One experiment we did that I liked a lot were when we tested the physical and chemical change in matter.  I liked this experiment because it was very hands-on, which I always like in an experiment.  The main ideas in these experiments were to realize that not everything is a physical change, based on what we can plainly see.  Another activity we did in class, that had the same idea as the previous activity, was when we recorded positive/negative/zero change and physical or chemical changes with the steel wool, precipitates, ice and water, alka seltzer, and the dissolving sugar.  We concluded that, most of the time, there was no change among the testers.  However, although there was no change, mass wise, there were a lot of changes between the physical and chemical aspects.  For example, with the steel wool, when we weighed it in the beginning, its volume was smaller than it was after we pulled it apart; the mass didn't change throughout the experiment.  So, even though its volume changed, its mass wasn't, and it was a physical change.  Another experiment we ran in this activity was when we combined two liquids to form a new substance.  In the beginning, one of the liquids was clear, and the other was pink.  Initially, I thought that after we would combine the two, the new substance would be an even lighter pink.  However, after we actually mixed them, it turned thick and turned a dark, blood-red color.  This contradicted my thoughts and made me think twice about what could happen in the future.   With this experiment too, when we measured the two separate liquids in the beginning, the mass didn't change after we combined them.  Instead, the volume increased.  This experiment was a chemical change as well, although the color of the new substance was different.  It was a chemical change because it made a new substance. 

In conclusion, after we ran all these experiments, I understood that there can be a physical or chemical change even though there isn't necessarily a change in mass or volume.  Throughout the past few weeks, I didn't really have any particular questions; I understood fairly well what I was doing in every task.  I think my participation in the learning process was good.  I participated often in class, as well as when we were in groups running the experiments.  I think I need to work more on going the extra mile, as far as getting the answers I need to the questions I do ask myself (when I think of questions).  

Video of my favorite part of the experiment we ran (burning the magnesium ribbon)