Wednesday, Janurary 5, 2011

Today Mr. H started off class by complimenting Emma on the blog post that she had completed the previous night with a quick review of the previous day using her blog as a guide. To begin class Mr. H started off class by giving us the answers to the reading sheet on pg. 36, but really pages 23 and 24. The answers are:
1-A
2-B
3-A
4-A,E
5-B
6-A
7-False
8-D
9-D
10-A,C
11-B,C
12-B
13-B
14-A,B,C,D
15-False
16-False
17-B
18-B
19-B

As usual, Mr. H walked us through the reading sheet by answering any questions we had or highlighting the key points on the reading sheet. The main focus of the discussion was on endothermic and exothermic reactions. We also learned about the difference between the system and surroundings. Next, we began to work in the packet for the second day and it was pretty exciting. The answers are below in the picture.

The first few questions weren't difficult because they started off distinguishing between basic endothermic and exothermic reactions. The top half of this page discusses this topic. Endothermic reactions are where the system absorbs energy from the surroundings cooling down the surroundings and exothermic reactions release heat/energy from the system heating up the surroundings. The second half of the page was a little more complex because it involved distinguishing what graphs represent which type of reaction. Also, more real world examples were used to help us grasp the concept of endothermic and exothermic reactions. Next, we moved onto pg. 3 of the packet and we got to use our calculators for the first time this unit, SWEEEEET!!

The questions on the following page involved understanding a mathematical concept. The equation that was essential was:

q=m*c*delta-t
q=a measure of the heat flow
m=mass of the substance that you are trying to find the heat flow for
c=heat capacity of the substance
delta-t=change in temperature over the reaction of the substance

We began to work on the problem, which was going to help us work on the lab TC2 that we had begun the day before. We were trying to find the heat flow of water to later find the specific heat of iron. In the equation, m was substituted with the mass of the water which was 100g, c was substituted with the heat capacity of water which is 4.18 and chart with heat capacity numbers can be found in our book in ch. 8. The change in temperature was from 21.9 degrees Celsius to the highest value of 29.5. So the equation looked like this:

100*4.18*(29.5-21.9)=q

Once we found q which was 2758.8 joules were needed to calculate the kilojoules lost by iron in the reaction, so we were able to conclude that the amount of energy water gained was the amount of energy that iron and that was -2.7588 KILOJOULES. The following equation was derived to find out the specific heat or heat capacity of the iron.

C= q/m*delta-t

When the known variables were substituted the equation looked like this:

-2758.8 J/(6.52)*(28.5-86.6)=c

The answer was 7.41 J/g*c.

Next, Mr. H gave us the directions, title and purpose Lab TC3: Heat of Fusion Lab. The goal of the lab was to determine the molar heat of the fusion of ice. We came back to the front of the room for a little bit as Mr. H explained to us how to complete the calculations to the Lab TC2 and TC3. It made it a lot easier to do. Most people didn't finish Lab TC3 and Mr. H said we would finish up the next day from help from him. That was the end of the class and Mr. H reminded us of our Webassign that was due which was a reading sheet.