Thursday, March 24, 2011
Wednesday, March 23, 2011
1. Mass of original water
2. Mass of water from melted ice (subtract mass of ice in water from the original water)
3. Change in temperature of water
13 degrees Celsius
4. Amount of heat lost by original
5. Heat Fusion for the Ice
1.Is the process of the ice melting endothermic or exothermic?
Endothermic. Heat is traveling on/into the ice.
2.Is the process of the ice freezing endothermic or exothermic?
Exothermic. The energy is traveling out of the ice.
We then continued on to the worksheets we had picked up in class. We had done #1 a & b in class. These are the answers we got as a class for that sheet:
1. CH4 + 2o2 -> CO2 +2H2O
a. 4.00 g of Methane (CH4) is allowed to burn according to the reaction above. The energy released by the reaction is used to head 800 grams of water from 15.0 degrees Celsius to 81 degrees Celsius.
-Find the energy released by the reaction in kJ.
800g x 4.18J/gºC x 66.4ºC = (app.) 222 kJ
-Find the moles of CH4 burned.
4.0g CH4 x 1mol/16.04g = .249 mol CH4
-Find Delta H in kJ/mol (including the sign) for the reaction above.
222kJ/.249 mols = 892 kj/mols
** remember delta H (which is heat associated with reaction)/ 892 kj/mol
b. In another experiment 1.55 g of CH4 is burned. How much energy would be released?
1.55 g CH4 x 1 mol CH4/16.04 g CH4 x 892 kJ/1 mol CH4 = 86.197 KJ -> 86.2 kJ
By the time we had gone over these problems in class, we were instructed to finish the rest of the two sheets for homework!
Monday, March 21, 2011
Finally we conducted the Heat of Fusions Lab. The procedure to conduct the lab can be found on the journal page he handed to us in class. It looks like this.
Sunday, March 20, 2011
Today for class we went to the auditorium to watch Mythbusters for a chem day. The Mythbusters episode was called "Crime & Mythdemeaners" and had to do with different security systems. We had to fill out a sheet with 30 questions having to do with the video.
The first part of the episode had to do with a fingerprint lock. They tried different methods of copying a fingerprint in order to trick the fingerprint lock. One of the questions we had to answer was:
What material was most like human skin?
Ballistic gel was used to make a fingerprint very similar to a human fingerprint so they could fool the sensor on the door.
The second part of the mythbusters episode had to do with thermal motion alarms. Thermal motion alarms take an average room temperature reading, and are set off when the temperature is changed by the presence of a person.
The third part of the mythbusters episode tested out an ultrasonic motion detector. The motion detector is set off when someone walks past it. The mythbusters thought that if the person is undetectable than the alarm would not go off. They tested this theory by having someone walk through the room with a big white sheet over them, and the alarm did not go off.
In the final part of the mythbusters episode the final myth had to do with filling up a safe with water than dropping an explosive with nitroglycerin into it making the door fly off with a huge explosion. This myth came from a movie where this was done, and the villain got away with the goods inside. After numerous failed attempts the mythbusters finally got everything to work our just how they wanted. At the end they finally dropped the explosive into the water like the movie, and a huge explosion made the door go flying. Everything on the inside of the safe was destroyed though so the movie was not too realistic.
Thursday, March 17, 2011
Here are the notes:
Average kinetic energy of the particles in a substance.
Units Used: Fahrenheit( we don't use this in class), Celsius and Kalvin.
Transfer of Energy (joules).........Can be gained or lost.
Tuckers Joke: " There's also dominicks and walgreens".....yaaaa? no comment
3. Heat loss and Gain
Endothermic- Gaining heat
Exothermic- Loosing Heat.
In between notes we did a quick observation of Mr Tuckers " Magic Blocks." One block was wood and one was metal. The wood block was warm, compared to the metal block. After putting a piece of ice on both blocks, the ice melted faster on the metal block!! This was all due to the energy transfer.
Graph on page 2 of notes ( at top of blog):
Part1.A Heating and Cooling of a solid
Heat (q)= M * Cp ΔT (Tf-Ti)
Part2B Melting solid <-> Liquid freezing
Heat= M * HF
Part3C Heating/Cooling a Solid
Heat (q)= M * Cp ΔT (Tf-Ti)
Part 4D Boil a liquid <-> Gas condenses
Heat= M * HV ( Heat Vaporization )
Part5E Heating/Cooling a Gas
Heat (q)= M * Cp ΔT (Tf-Ti)
Wednesday, March 16, 2011
Friday, March 11, 2011
if reaction shifts left, then NO2 and O2 increase and NO3 decreases on the graph
the opposite of decrease temp in INCREASE TEMP so shift left towards the heat
Decrease H2- shift left
Add a catalyst…… skip, do not worry
Increase volume…..skip, do not worry
a) True, if K is greater than 1 the products are favored (K = P/R)
15. First, find the concentrations of all substances by dividing mols by 5L
From top left to right
a) about 98.6F, Homeostasis…like hair and shivering
b) about 98.6F, Homeostasis, like sweating
c) Yes, body keeps changing in response to external conditions
d) House heats up, thermostat increases, air conditioner turns on, House cools down, Thermostat decreases, air conditioner turns off
e) Body changes OPPOSITELY in response to stresses(changes) on it…it tries to fix itself.
a) Temp, Time
b) Amounts of A and B
c) about 1-2seconds
d) Inverse, as T goes up, time goes down
e) Cannot predict, A may not react with C
a. K= [P] / [R]
b. K = [NO2]2 x [Br2] / [NOBr]2c) NOBr- 109.9g/mol, NO- 30g/mol, Br2- 159.9g/mol
d) NOBr- 0.910 mol, NO- 0.333 mol, Br2- 0.625 mol
f) mol / L
g) NOBr- 0.182M, NO- 0.0667M, Br2- 0.0125M
h) K= 0.00168
a) double arrow
b) forward reaction = reverse reaction, concentrations of reactants and products are constant
c) +, reactant side…….do not worry, I will always tell you what side the heat is on for now
d) 2mols reactant, 3 mols product
e) More, Less
g) add SO2, right, SO2 and O2, SO3, more moles gas, increase
h) decrease O2, left, SO3, SO2 and O2, less moles gas, decrease
i) decrease temp, right, SO2 and O2, SO3, more moles gas, increase
j) increase pressure, right, SO2 and O2, SO3, more moles gas, increase
Thursday, March 3, 2011
WE JUST WROTE THIS LAB IN OUR JOURNALS!!
Procedure: Place 1/4 alka seltzer tablets in 25ml of water in a 50ml flask and place a balloon over the top of the flask. Time how long it takes for the balloon to inflate. Repeat with 1/2 and full tablets.
1/2 tablet- 14sec
1 tablet- 6sec
Conclusion: As concentration increases, so does the speed of the reaction
Preocedure: Place 1/2 alka seltzer in in 25ml of water in a 50ml flask and place a balloon over the top of the flask. Time how long it takes for the balloon to inflate. Repeat with a crushed alka-seltzer (which has more surface area!)
1/2 tablet - 16sec
1/2 tablet crushed- 5sec
Conclusion: As surface area increases, so does the speed of the reaction
Procedure: Place 1/2 tablet of alka-seltzer in 25ml of room temperature water (22 degreesC) in a 50ml flask and place a balloon over the top of the flask. Time how long it takes for the balloon to inflate. Repeat this with 5degreesC water and 50 degreesC water.
5C- 2min, 20sec
Conclusion: As temperature increases, so does the speed of the reaction
The independent variables for the lab were concentration, surface area, and temperature
The dependent varibale for the lab was time / speed of the reaction
The controlled varibales for the lab were the size of flask, type of tablets, and amount of water.