We first started class off today by being told by Mr. Lieberman that we will not be doing our lab today, but we will be doing it on Monday instead.
Next we went over our pre-lab. I want to thank Matt P. with some help from Ben A. for explaining to us how to answer each question. Here is how to do them:
1) Make an equation to help find the pressure of hydrogen: 19.8+x=746 and when you solve for x you get 726.2 mmHg of H2.
2)Use your answer from #1 and you will make an equation following the form of PV/T=P2V2/T2. The equation is 726.2(31)/295=760V/273. Solve the equation for the volume of hydrogen at STP and you should get .274 L.
3)This is just a simple stoich problem: .028g Mg x 1 mole Mg/24.3g x 1 mole H2/1 mole Mg =.001167 moles of H2
4) Use your answers from numbers 2 and 3 to get the molar volume of hydrogen at STP: .274/.001167 = 23.5 L/ 1 mole.
Next, after going over the pre-lab, we continued going over notes. The main thing we talked about in our notes is that there are three equations that come from the equation PV=nRT. Those three equations are:
-PV=(g/mm)RT
-mmP/RT=g/v and g/v equals density
-mm=DRT/P~ a way is to remember this is dirty pee...get it..
Also, a reminder, make sure you are keeping up with your worksheets which are due on the day of the test which is on Friday, the day before break.
Then we did an awesome experiment that we were actually able to eat. We made chocolate ice cream! The ingredients were sugar, milk, whipping cream, chocolate syrup, and what made the magic happen, liquid nitrogen. It was and looked a little clumpy, but it actually tasted really good. And that was the end to another good day in chem.
The next scribe will be......Kaitlin Y!
Friday, December 10, 2010
Thursday, December 9, 2010
Gas gas gas
Half of our classmates were gone today...
because of ....... don't know...
Denna wasn't here today so I am the scriber for today
We started the class with a demontration. Mr. Liberman put some melted dry ice into a styrofoam box and put a manometer,this manometer has a empty metal ball, into that box. And the pressure went down because the moles which is in that ball starts to move slow. Through this experiment we could make sure that when temperature goes down then pressure goes down and temperature goes up then pressure goes up.
After Mr. Liberman finish off with this experiment, we wanted him to dump the melted dry ice on the floor.
And he did....Twice :)
The melted dry ice started to move around the floor like when we spill some water on the hot pan.
We were all excited about the movement of these little particles.
Also Mr. Liberman dumped the ice over my head accidently!
Korri screamed and called 911 immediately
So that's why I am in hospital right now...
hehe I'm just kidding~
Actually he poured vapor over my head. It just feel coooool~
Today, we learned about the Ideal Gas Equation.
The three important gas laws, Boyle's, Charles', and Avogadro's, derived relationships between two physical properties of a gas, while keeping other properties constant.
When we rearrange to a more familiar form we get PV = nRT
*In this equation R is the gas constant.
The conditions 0 *C and 1 atm are called Standard Temperature and Pressure (STD).
At STR R = (1 atm x 22.414L) / (1 mol x 273 K)
R = .0821
And experiments show that at STP, 1 mole of an ideal gas occupies 22.414 L.
If you know the formula with STD, we could convert to different forms.
The important thing is the value of R won't change!
Here is an example
What is the volume(in liters) occupied by 49.8g of HCl at STP?
T = 0*C = 273K
P = 1 atm
n = 49.8g x (1 mol / 36.45g HCl) = 1.37 moles
V = (1.37 mol x 0.0821 x 273 K) / (1atm)
V = 30.6L
I hope you guys understand what I explained...
If you want more information about the ideal gas equation, I recommended to visit :
Today's homework is a Worksheet and Pre-Lab
The next scribe will be Denna M.
Wednesday, December 8, 2010
What it really Boyles down to
Today we started by quickly reviewing Dalton's Law and Boyle's Law, with a couple more gas chamber experiments. he sucked all of the air out of the container (after realizing he needed to attache the hose) and made shaving cream get big, unfortunately he stopped it before it made a mess. He also did an old marshmallow which was rather uneventful.
Then we went on to discuss conversion between temperatures of celcius and kelvin because it is necessary to know for formulas. The reason you need to know the Kelvin temperature is because if you use celcius you may end up with correct calculations stating that you ave negative density, which i hope all of you know is "impossible" according to Mr. Lieberman. To convert celcius to Kelvin all you need to do is add 273 degrees to the celcius measurement.
Then as we continued our notes we went on to Charles' law, which states: The volume of each gas is directly proportional to temperature. V=bT where b is a constant and V1/T1=V2/T2. This means that the original volume over temperature will be equal to the new volume over temperature. To explain this to us he showed us a quick experiment by heating to small flasks with water until they boiled, he then stuck a balloon on top of one which was still boiling and the balloon filled as the gas expanded. he stuck another balloon on top of the other right after removing it fro the heater, the balloon was quickly sucked into the flask because of the rapid change in temperature and the fast reduction of volume.
Next D Liebs quickly explained Avogadro's law which states: Volume is directly proportional to the number of moles of gas. To show this he simply blew up a balloon and let go, letting it soar around and land on Alex's desk. This demonstrates that as moles of air are released there is less and less volume and pressure to keep the balloon inflated, so it eventually collapses. then there is the infamous combined gas law which is P1V1/T1=P2V2/T2 this can be used to apply all forces to one equation instead of several different ones.
There was also a sheet to pick up at the front when we walked in, that sheet is homework and is due come test day. Speaking of which is next friday, the friday right before break. Also, everyone check out the little map thing to the right, people all over the world have seen our blog!
Then we went on to discuss conversion between temperatures of celcius and kelvin because it is necessary to know for formulas. The reason you need to know the Kelvin temperature is because if you use celcius you may end up with correct calculations stating that you ave negative density, which i hope all of you know is "impossible" according to Mr. Lieberman. To convert celcius to Kelvin all you need to do is add 273 degrees to the celcius measurement.
Then as we continued our notes we went on to Charles' law, which states: The volume of each gas is directly proportional to temperature. V=bT where b is a constant and V1/T1=V2/T2. This means that the original volume over temperature will be equal to the new volume over temperature. To explain this to us he showed us a quick experiment by heating to small flasks with water until they boiled, he then stuck a balloon on top of one which was still boiling and the balloon filled as the gas expanded. he stuck another balloon on top of the other right after removing it fro the heater, the balloon was quickly sucked into the flask because of the rapid change in temperature and the fast reduction of volume.
Next D Liebs quickly explained Avogadro's law which states: Volume is directly proportional to the number of moles of gas. To show this he simply blew up a balloon and let go, letting it soar around and land on Alex's desk. This demonstrates that as moles of air are released there is less and less volume and pressure to keep the balloon inflated, so it eventually collapses. then there is the infamous combined gas law which is P1V1/T1=P2V2/T2 this can be used to apply all forces to one equation instead of several different ones.
There was also a sheet to pick up at the front when we walked in, that sheet is homework and is due come test day. Speaking of which is next friday, the friday right before break. Also, everyone check out the little map thing to the right, people all over the world have seen our blog!
Also since Ben never posted any hilarious pics that im sure everyone wants, here is zoë, looking as happy as a person being vacuum sealed.
Tuesday, December 7, 2010
The pressure is on
Today in class, we learned about pressure and saw a few demos. We saw Mr. Lieberman lay down on a bed of nails, and then a few of us got to try as well. The reason people didn't get stabbed to death by the nails is that pressure equals force divided by area (P=F/A). He explained that no matter how big or small an object is, the force remains the same. The dependent part is the area. The bigger the object on the nail bed, the less pressure is on them due to the increase in area.
http://www.flickr.com/photos/hc1011/5241587429/
We also learned the different units for measuring pressure, and the conversions between them. They are: pounds per square inch (psi), atmosphere (atm), Torr, or millimeters of mercury (mmHg), and pascal (Pa). The conversions are: 14.7 psi=1 atm=760 mmHg=100 kPa. We also went over how barometers and manometers work, with the atmosphere pushing down to show the pressure.
We went over Dalton's law too, which states that the sum of partial pressures of gases equals the total pressure of the gases when combined. So, if gas 1 is 1 atm and gas 2 is 2 atm, when they are combined the pressure is 3 atm. Boyle's law deals with pressure and volume, stating that the product of the pressure and volume for a gas equals a constant, k (PV=k). So no matter what differences in pressure or volume occur, P1V1=P2V2.
We also got to see Brandon and Zoe get stuffed in a trash bag and have the air sucked out to demonstrate the actual air pressure here on earth, as well as see an inflated balloon expand when the air is sucked out. Happy late arrival tomorrow, and the next scribe is Peter W.
http://www.flickr.com/photos/hc1011/5241588237/
http://www.flickr.com/photos/hc1011/5241588451/
http://www.flickr.com/photos/hc1011/5241587429/
We also learned the different units for measuring pressure, and the conversions between them. They are: pounds per square inch (psi), atmosphere (atm), Torr, or millimeters of mercury (mmHg), and pascal (Pa). The conversions are: 14.7 psi=1 atm=760 mmHg=100 kPa. We also went over how barometers and manometers work, with the atmosphere pushing down to show the pressure.
We went over Dalton's law too, which states that the sum of partial pressures of gases equals the total pressure of the gases when combined. So, if gas 1 is 1 atm and gas 2 is 2 atm, when they are combined the pressure is 3 atm. Boyle's law deals with pressure and volume, stating that the product of the pressure and volume for a gas equals a constant, k (PV=k). So no matter what differences in pressure or volume occur, P1V1=P2V2.
We also got to see Brandon and Zoe get stuffed in a trash bag and have the air sucked out to demonstrate the actual air pressure here on earth, as well as see an inflated balloon expand when the air is sucked out. Happy late arrival tomorrow, and the next scribe is Peter W.
http://www.flickr.com/photos/hc1011/5241588237/
http://www.flickr.com/photos/hc1011/5241588451/
ChemThink gases
Yesterday in chemistry, we went over our new unit, which will end on Friday the 17th with the unit test. After that, we went on the computers to do a ChemThink on the properties of gases. We learned that gas atoms can be affected by temperature as well as size, which changes their speed. We also learned that the pressure of a gas equals its force divided by area. Pressure is caused by gas atoms' impact on the sides of their container. Pressure goes up as the temperature rises due to the fact that there are more collisions, and that they're more forceful. Also, as the number of atoms rises, the pressure rises because there are more collisions. As the volume of the container increases, the pressure goes down because there are less collisions. So overall, we looked at four properties of gases: temperature, pressure, number of atoms, and volume.
Subscribe to:
Posts (Atom)