Light

Hello

Today was a simple class. We just went over the notes.

First we talked about the wavelengths and frequencies of different types of light.

The types of light on the left side of the electro magnetic spectrum have a high frequency and small wave length. The types of light on the right side have a low frequency and a large wavelength.

As the frequency goes up, the wavelength goes down.

Mr. Lieberman used an example. If you are standing on an overpass looking down at two lanes, one of which has semi trucks in it and the other has sports cars in it, the lane with the sports cars will have a higher frequency because more cars can pass by in a given amount of time. The lane with the semi trucks in it will have a lower frequency because less trucks can pass by in a given amount of time, but will have a higher wavelength.
We then took out our cell phones and looked at the infrared light given off through the remote.

Then we learned about the equation for speed which is, wavelength(frequency)=speed.

We aslo learned about Planck. He stated that the transfer of energy is not continuous. His equation for change in energy is: change in energy=hv

h=Planck's constant= 6.626X10^-34 Js

A higher frequency=more energy

A lower frequency= less energy

Einstein stated that electromagnetic radiation was made up of a stream of particles known as photons.

A man named Louis de Broglie connected the two theories about light (that it was in wavelengths or in streams of particles) to make an equation: wavelength=planks constant/mass(velocity)

The last thing we did was put on 3D glasses and look at the lights on the ceiling. We a continous spectrum of light. After that Mr. Lieberman turned on a helium and mercury light and we saw a line spectrum.

Thats we learned about.

The homework is to do the top of the worksheet we got.

The next scribe is Erika

test

it will be monday

Spontaneous reactions, Entropy and Gibb

Hey everyone~

Sorry about not posting yesterday :(

But otherwise, i'll be explaining yesterday and today's day in Chemistry.

On Tuesday, Mr. Liebs explained Spontaneous Reactions and Entropy (\DeltaS).

Although it's all in our notes, I'll just summarize the basic points:

Spontaneous Reactions: a process that takes place on their own, without outside forces

Some examples are...

- ice cubes melting when added to water at room temperature

- mixing hydrogen and oxygen to form water when a spark is applied

- iron rusting because it's exposed to moist air

(These reactions will happen no matter what, in these given conditions)

Entropy

Nature tends to move spontaneously from an orderly state to a random/disorderly state (a process known as the randomness factor).

And connecting with this "randomness" idea is entropy: an increase in disorder or randomness shown as \Delta S

Entropy is highest in this order of states: solid <>

When using entropy in reactions, the equation is \Delta S =\Sigma \Delta S (products) - \Sigma \Delta S (reactions)

Note: when calculating entropy, the coefficients should be a part of the equation (multiplied to each term, accordingly)

On Wednesday, Mr. Liebs continued on with another explanation of notes on Gibb's Free Energy: the energy in the system that is available to do useful work.

A reaction can do useful work if it's spontaneous; and whether or not it's spontaneous can be found through this equation: \Delta G = \Delta H - T \Delta S (as long as temperature and pressure are constant)

Note: In the latter equation, 'T' or temperature has to be in Kelvin)

We will know if the reaction is spontaneous by knowing if \Delta G is a positive or negative value.

If \Delta G is negative, the equation is spontaneous

If \Delta G is positive, the reverse equation is spontaneous

[Look at Table 17.2 in the textbook for more information]

Homework:

Tuesday's homework: Hess' Law Lab

Hess' Law Worksheet

Wednesday's homework: Gibb's Free Energy Worksheet

WebAssign

AND THURSDAY'S TEST WILL BE MOVED TO FRIDAY BECAUSE OF THE SNOW DAY!

So have a fun snow day tomorrow! :)

And the next scribe will be....... Paige H.

Hess's Law Lab

Friday was a pretty simple day in Chemistry. We started off class by going over the procedures for Hess's Law Lab. Here are some tips that might help you with the lab: When you are trying to find the heat of reaction for Reactions 1 and 2 you have to use q=mc∆t. Once you find J, all you have to do is divide that by 1000 to put it into kJ and then divide the kJ by the moles of magnesium/ magnesium oxide used in the experiment. Once you find the heat of reaction for both experiments, use Hess's Law to find the heat of reaction for the combustion of magnesium.

And the next Scribe is Rachel K.

Hess' Law

The class started off today with Liebs showing us the experiment that failed yesterday. He was showing us how the process of sublimation could change to fusion. In order to do so he put frozen carbon dioxide, or dry ice, under "intense" amounts of pressure.

Once the dry ice melted under the water, it would pop under the pressure and send water everywhere, which was terrifying to some of the people in our class... so this is is the same thing, but without the "pop".



Moving onto the lecture today, we spent the rest of class discussing something called Hess' Law. Hess' Law basically says that you can use multiple ways to find Hess' Law, and it will still work, as long as you come to same, correct conclusion.

"If you ski down a hill, it doesn't matter the path you take, you're still going to get to the bottom. As long as you don't hit a tree."

Basically you are given a formula, and you must add and subtract a series of other equations to match it, and then do the same process to series' delta H's in order to find the original missing delta H. To change the equations you can do one of two things: you can flip the formulas around or multiply their coefficients by a number. When adding the equations, if they are on the opposite side of the arrow and the same element/compound they cancel. If they are on the same side then they combine.

An example:

If at Once you don't Succeed Try, Try Again.

That saying above doesn't apply for our class today. We were learning about Phase Diagrams:

The Phase Diagram above is on Water!!! So the shaded blue part is where at a certain temperature and pressure the water is a Solid (such as Ice). The shaded green part is where the water is a liquid (Aka water). The shaded pink part (sure i guess you can call it peach) is the water as a gas. (The actual H2O molecule, not O2 or H2 molecules) Anyway...the places where the lines separate the three areas are where the change between the phases happen. The temperature is always on the X-axis and the pressure is always on the Y-axis. The lines tell the points at which the change takes place, but there is almost always a 'normal' melting or 'normal' boiling point. Which for water is 0 degrees Celsius and 100 degrees Celsius. The point on the graph that says "Triple Point" is where at this certain pressure and temperature the substance will be in all three states. We actually saw this happen in one of the demo's Mr. Liebs showed us... I couldn't find a picture of the triple point of nitrogen so I'll just use the picture of water...

As you can see, the Liquid is on the bottom, the Solid is in the center and the Gas is on the top. (trust me the gas is there). The critical point is where the liquid is not a solid, liquid, or gas actually. I know it's hard to believe...but it's true. Liebs tried to show us that it was true with dry ice, but we couldn't get a good enough seal on the container so it didn't work. We tried to seal it many, many times but in the end all we had was a broken ego and a wish to see the critical point. So as you can see, 'if at once you don't succeed try, try again.' doesn't always work. But being as optimistic as we are, we will try it again tomorrow. So either it will work, or we will fail...again.

http://http//www.youtube.com/watch?v=2Z6UJbwxBZI&feature=related This video posted here (look up) is about the critical point of helium. (sorry i still can't get the video into the actual blog)

We were trying to do the same thing with carbon (aka dry ice) but as I said earlier we couldn't get a good enough seal. Also in the video you will hear the word Viscosity. That means the thickness or thinness of a liquid (also used for oils, if anyone needs to put oil in their cars they look at the viscosity to make sure it's right).

Boiling occurs when the vapor pressure and the pressure from outside are equal, or when the vapor presser exceeds that of the outsides. During the Critical point the meniscus:

disappears and the point where liquid and gas are separated is nonexistent:


As you can see, the meniscus has disappeared.
Another thing we learned is the term Sublimation, this is when the solid changes to a vapor totally skipping the liquidation phase.
Please don't forget about the two web assigns. One has been extended from Monday, and is now due tomorrow, then also the web assign that is due on the 31st is up. We also have work sheets that are due on the day of the test.
The Scribe for tomorrow is...Erika G.!!!!!!!!! YAY!!!!! Good Luck Erika! And again sorry about the video, I'll figure it out by next time!!!!!

Heat

Well, today was the second day of second semester. We started off class by having Mr.Lieberman show us how to do the graph for the lab we did yesterday. Basically when doing your graph you will beableto notice three distinct regions on the graph. These regions can be identified on the heat curve shown below.

As you can see the first region is where the snow(solid) turned in to water. The second region is just the liquid stage. After this stage there is the region where the water turned into steam. The first and third region are both endothermic. When we finished discussing this Mr. Lieberman told us of the possible error that we might find with our lab results. He said that for some of the data we might have gotten the temperature of the hot plate rather than the water. This would be if we let the thermometer touch the bottom of the beaker when recording the temperature.

When we finished talking about the lab, we worked on the worksheet that we picked up in class today. If you did not get it, you can get it on moodle. Also, if you finished the worksheet and want to review your answers you can get that on moodle as well.On this worksheet two new concepts were introduced, Heat of fusion and Heat of vaporization. The heat of fusion is used for the melting point, and the heat of vaporization is used for the boiling point. These can be found in our textbook.

Mr. Lieberman also did a demo today. Basically it proved if steam or liquid water could get hotter. To do this Mr. Lieberman burned a piece of paper only using steam. This helped to prove that vapor burns were more sever than liquid ones.

Remember that we have a WebAssign due tomorrow as well as the worksheet and lab from Monday.

The next scribe is Danielle D. Have fun!