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.

Specific Heat of Metal Lab

Hey everyone~

So we started class by looking over two of the problems from the worksheet: 8 and 9.

Mr. Liebs explained that problem 8 can be done by setting the amount of energy for copper equal to the amount of energy for water. Knowing that, you can use the law of thermodynamics to solve for the mass of water:

q Copper = q Water

(110)(0.2)(57.5)=(4.18)(2.6)(m)

m= ______

In problem 9, you find the specific heat capacity using the law of thermodynamics again. Once you have calculated the specific heat capacity, you convert moles (because the question asks for you to solve for the molar heat capacity of mercury). You can easily convert it by knowing that the unit for specific heat capacity is J/g C and that the grams of mercury is over 1 mole:

585J=(125.6g)(53.5-20.0) c

c= 0.14 J/gC

0.14J/gC x 200.51g/1 mole = ______

Check the answers on moodle!

After the worksheet, we moved onto our lab: The Specific Heat of Metals Lab

We were assigned to work with our partners and follow the procedures from the lab, which was basically just to...

1. collect a dry test tube and measure the mass

2. mass the test tube with a given metal

http://www.flickr.com/photos/hc1011/5324135903/

3. heat up a beaker full of water until it is boiling

4. Put the test tube inside the boiling water for 10 minutes

http://www.flickr.com/photos/hc1011/5324740964/

5. Fill a calorimeter with about 50 mL of water and measure its volume

6. Then measure the initial temperature

http://www.flickr.com/photos/hc1011/5324740468/

7. After the 10 minutes are up, place the test tube inside the calorimeter and measure its final temperature.

http://www.flickr.com/photos/hc1011/5324136951/

After recording each of these measurements, complete the rest of the lab for homework.

The next scribe is... Paige H.

Santa in a Snow Storm!!

So I just got these pictures from Santa as he was making his way across the east coast.

Actually this demo is sometimes called "Santa in a Snow Storm" and illustrates a great chemical concept. Your extra credit assignment if you choose is to submit electronically a chemical explanation of the demo using concepts that we have discussed first semester. This must be turned in "electronically" by 1/3/2011 @ 8 AM. Yes you have freedom off how you want to turn this in. Good Luck and Happy New Year

Turn and face the change

Today we continued our discussion on changes. In the previous lab (separating mixtures) we exclusively looked at physical changes. In today's lab we will look at chemical changes.
First we discussed the differences between physical and chemical changes/properties. Here are the notes from class

Physical properties

View more presentations from gbsliebs2002.

Some key points from the lecture

Does this really need an explanation?

• The difference between a change and a property is a matter of symantics. We will not be asked to distinguish between the two.
• Physical or Chemical properties are characteristic properties that can be used to identify an unknown substance. All you have to do is look them up.
• People often get confused with phase changes. Boiling, melting, etc are physical changes because they do not change the make up of the substance.
• Chemical changes take the original substance and make a new substance(s). The example that was given was gasoline burning in oxygen to form carbon dioxide (CO2) and water (H2O) 

After the lecture on physical/chemical changes, we went over the pre-lab for the chemical reaction lab. We specifically went over the first question about the signs of a chemical reaction

• light emission
• temperature change
• bubbles 
• precipitate formation
• color change

After the pre-lab discussion, we started the lab but had barely enough time to to finish part A. Rachel M will be the next scribe and she will talk about the lab

Photos

The easiest way that I have found to post photos to the blog from flickr is this:
1. go to my flickr photostream and click on the photo that you want to place in the blog.
2. Above the photo is an actions tab: click the actions tab and select view all sizes.
3. Choose the size photo that you want...I usually choose small. Right click on the image and select save as...
4. Save the image to your desktop.
5. In Blogger, click on the insert image and upload the image to the blog.
Let me know if you have any problems with this

Safety Part 2

Today's class we continued our discussion on safety and started to prepare for our first lab. We watched another clip from the ACS safety video. This shorter clip had to do with good lab techniques. There are several points that I think are worth highlighting.

1. The video made a point of telling us that it is always smartest to pour liquids from large stock bottles into smaller containers that are easier to manage in the lab.

AHHHH...the memories

2. The point of mixing acids is an important one but not done very often in our class. Acids should always be poured into water, not the other way around. "Do what you outta pour the acid into the watta" I know lame but I learned that in high school myself.

3. The video also commented on how we always pour out of stock bottles but never back in. If you have too much of a chemical dispose of it properly but do not put it back into the stock bottle.

4. Remember never mouth pipet!!

After that we briefly discussed how to do the pre-lab for Monday's Observation Lab. We will discuss the data tables on Monday also. Lastly we briefly talked about the unit objectives that were handed out. These are just the main topics for the current unit. They will be handed out at the beginning of each unit. Remember that if you missed a handout for an absence please go to our moodle site to download them. The last thing we did was took our safety assessment on WebAssign.

V-I-C-T-O-R-Y

Have a great weekend and go Titans!!
Oh yeah our first student scribe is...Erika G.

Safety Dance

Today was all about safety. Our discussion centered around the Flinn Scientific Safety Contract. Also we watched clips from the ACS safety video. The first part of the discussion talked about appropriate laboratory attire and behavior. The movie clips were hilarious but informative as Mr. Lieberman was able to link them to our classroom. He showed us the location of all the safety equipment and some special safety considerations for our classroom. The second part of the discussion talked about what to do in case of an emergency our an accident in the laboratory.



Mr. Lieberman also showed us some cool demos that go along with the discussion. The first demo involved "Dave" the mannequin and acetone. This showed us how ordinary household substances can be dangerous in the lab and also how "horseplay" can result in serious injury. The second demo involved an egg and concentrated sulfuric acid. This showed us how sensitive the tissue in our eyes is and how quickly an eye injury could occur. The last demo was the vapor ramp demo. This showed the volatility of organic compounds and how we need to be careful with them near upon flames as the vapor is extremely flammable.

Now that we are all experts on safety...let's dance!!

Creating A Post

The video below will help you with how you create a post in our class blog:





There are two types of posts that you will create: 
   1. Scribe Post (scribe):  This is a daily entry of what happened in class that day
  2.   On My Mind (OMM):  This is an entry that you submit at any time to share something that is on your mind.

Every post should have at least three labels:
  1.  "scribe" for a scribe post or "OMM" for an on my mind post
  2.  your username
  3.  the topic addressed in the post

Digital Ethics

Blogging is a very public activity. Anything that gets posted on the internet stays there. Forever. Deleting a post simply removes it from the blog to which it was posted. Copies of the post may exist scattered all over the internet. That is why we are being so careful to respect your privacy and using first names only.

There are four principles from which we will operate as we create digital content that will be posted on the internet.


1.  Students using blogs are expected to treat blogspaces as classroom spaces. Speech that is inappropriate for class is not appropriate for our blog. While we encourage you to engage in debate and conversation with other bloggers, we also expect that you will conduct yourself in a manner reflective of a representative of this school.


2.  Never ever give out or record personal information on our blog. Our blog exists as a public space on the Internet. Don’t share anything that you don’t want the world to know. For your safety, be careful what you say, too. Don’t give out your phone number or home address. This is particularly important to remember if you have a personal online journal or blog elsewhere.


3.  Again, your blog is a public space. And if you put it on the Internet, odds are really good that it will stay on the Internet. Always. That means ten years from now when you are looking for a job, it might be possible for an employer to discover some really hateful and immature things you said when you were younger and more prone to foolish things. Be sure that anything you write you are proud of. It can come back to haunt you if you don’t.


4.  Never link to something you haven’t read. While it isn’t your job to police the Internet, when you link to something, you should make sure it is something that you really want to be associated with. If a link contains material that might be creepy or make some people uncomfortable, you should probably try a different source.



- Parts of this post were taken from a digital ethics post by Darren Kuropatwa.