ChemStd 9a: Le Chatelier's Principle

First of all, what is Le Chatelier's principle? If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.

In essence, whatever is added to the equation or shifts the equilibrium, Le Chantelier's principle states that the equation will automatically shift to counter this change and maintain an equilibrium; it will do exactly the opposite of whatever is disrupting the equilibrium.

• Effect of the change in concentration:

CO + 2 H₂ ⇌ CH₃OH

If more CO was added, then according to Le Chantelier's principle, the amount of CH₃OH would increase also. Whenever there is a change in concentration, the opposite side of the equation will experience a similar change, whether a decrease or increase of molecules.

• Effect of the change in temperature:

N₂ + 3 H₂ ⇌ 2 NH₃ + 92kJ

In the above equation, it shows heat is part of the product, making this an exothermic reaction. If the temperature increases, the equilibrium will shift to the side that does not have heat to create a balance and decrease the temperature, which is to the left. Decreasing the temperature will shift the equilibrium left, towards the reactant.

H₂(g) +I₂(s) + 52 kJ ⇌ 2HI(g)

In this equation, heat is part of the reactant, making this an endothermic reaction. Increasing the temperature will cause shift the equilibrium right, however, decreasing the temperature, shifts the equilibrium toward the left to balance the equation at a constant temperature.

• Effect of the change in pressure:

2NO₂(g) ⇌ N₂O₄(g)
An increase in pressure results in a shift towards the side with the least molecules, which is N₂O_{4. A decrease in pressure however causes the equilibrium to shift to the side with more molecules to counter the decrease in molecules and maintain an equilibrium; in this case} 2NO_2.

For a full complete explanation of Le Chantelier's Principle:
http://www.youtube.com/watch?v=Ywzvzw6Rdpk

Rock Candy!! (a chemistry mini project)

How to make rock candy...

You need:
-sugar
-water
-spoon (to mix the sugar and water solution
-hot plate (to heat the sugar and water solution)
-life saver candy
-string
-Popsicle stick
-beaker or jar

Procedure:
-mix sugar and water together and heat at a high temperature until the sugar is dissolved.
-take the string, tie one end to the Popsicle stick and the other end to the life saver (through the hole in the candy)
-coat the hanging string with the life saver with dry sugar.
-pour the sugar and water mixture into the jar or beaker.
-balance the Popsicle stick on top of the jar so the life saver hangs down but DOES NOT touch the bottom of the jar.
-wait, and watch, you should see some crystals that grow in a 3-7 days!

The science of crystals:
Precipitation: The sugar and water solution is supersaturated, meaning there is more solute (sugar) than water. A supersaturated solution is unstable and so the solute is pushed out from the solution and a precipitate forms.

Evaporation: as days past, the water slowly evaporates from the solution, making it more saturated, which forces more sugar to cling to the string. The crystals slowly build on each other until you eventually have your rock candy.

Photo credit: Rachel Kawawaki!!

USMAIL (say it fast and it sounds like U SMELL) (a chemistry mini project)

Smells, when I think of them I automatically think of the chocolate factory by our school and how during brunch we can smell the delicious chocolate that wafts over the school walls. But what makes it so you can smell the smell of fresh baked cookies in the living room, or the odor of the porter potty down the street. It's all due to diffusion.

It was mother's day on Sunday and my cousin brought these beautiful pink roses for the mothers in our family. They were put in a vase and after a while, we sat down to watch the Suns vs Spurs game and after a while, I started to notice this lovely flowery scent. It smelled really nice, but I wondered how I could smell it from all the way across the room!

Molecules naturally move from a high concentration to a low concentration. Since the smell of the flowers were highly concentrated in one part of the air, the smell (molecules) would gradually mix with the unscented molecules to try and create an equilibrium. This is why a scented candle makes the whole room smell nice.

Another experiment you could try with this is simply:
1. spray a febreze bottle into the air
2. wait for a while then see if you could smell the scent.
3. have several people with you, one in front of the other, so that you can see the gradual diffusion of the molecules over a period of time. (the person closest to the sprayed molecules should smell the scent first, gradually working back to the person furthest away.)

Photo credit: my dad!

Lets Make Play Dough!!! (a chemistry mini project)

In class we made play dough using:
- 1 teaspoon of oil
- 1 cup of flour
- 1 cup of sugar
- 1 cups of water
- couple drops of food coloring

We mixed all of together at high heat and stir the mixture until in becomes more puddy and manageable and then we took it out, coated it with flour to not make it so sticky and then presto, you have play dough!! Now you can make whatever shapes you want with it, a star, a heart, one guy even made a mini tank!!

The chemistry behind it:
Flour is held together by hydrogen bonds, however, using the sugar we were able to transform the molecular structure and cut the hydrogen bonds, creating the dough's new texture of play dough.

Photo credit: Rachel Kawawaki! :)

Brownies anyone?? (a chemistry mini project)

So for my mini chem project, I decided to make brownies!!! What's so scientific about brownies you say? Well here's the answer (according the the various websites I researched):

- Flour is used to make the bread or whatever you're baking to supports the ingredients as it rises. In the case of bread, CO2 bubbles are released to make the bread light and airy.
- Sugar is almost like a catalyst, it feeds the yeast, causing the CO2 reaction to happen faster.
- Baking Soda forms CO2 in this equation: NaHCO3 + H+ → Na+ + H2O + CO2.
- Eggs are used to keep the CO2 from escaping too soon and also to bind the ingredients together.
- Fat (butter) gives what you are baking a lighter texture.
- Why so much talk about CO2? It's because CO2 helps the dough rise, and that's definitely important when it comes to talking about bread!

So anyways, here's the ingredients for the brownies I made (based off of Food Networks' Ina Garten):
- 1 pound unsalted butter
- 1 pound plus 12 ounces semisweet chocolate chips, divided
- 6 ounces unsweetened chocolate
- 6 extra-large eggs
- 2 tablespoons pure vanilla extract
- 2 1/4 cups sugar
- 1 1/4 cups all-purpose flour, divided
- 1 tablespoon baking powder
- 1 teaspoon kosher salt
- 3/4 cup smooth peanut butter


The recipe actually called for stiring the eggs instead of beating them, and since the egg yolk is used to keep the CO2 from escaping, and CO2 is used to help the brownies rise, My brownies ended up to be almost 2 in tall!! I think I overcooked them a little, but they were still delicious! This sure was a yummy project!

Photo credit: my dad! :)

Mills Creek Canyon Park!!!!

On Thursday all of Mr. Olson's class took a field trip to Mills Creek Canyon Park. As you can see in the map below, we walked all the way there. I can assure you, that the walk up Martinez Dr. was not easy. It was fun though, just being able to take a break from the classroom and enjoy the sun and everything else nature had to offer. There were about 150 some kids I think, so it was kinda of chaotic, but still awesome to hang out with friends. It was hot because we were walking up pretty steep hills and all, and the ground was muddy from the rain the previous day, but I think most of us did not mind it so much.

I didn't see many animals, well, actually, I saw a dead lizard in the street and a rolly polly but no birds or little critters. I did get to enjoy the green trees, and beautiful flowers that were in full bloom. They were gorgeous! The view was also pretty cool and we could see the houses and the airport at one point in the hike.

We walked around following the trail for an hour and then we ate lunch and socialized. Some people went back down to the creek and I know my friends found this secret trial of some sort and played in a hammock that was hanging on the tree. I had to leave early because of a swim meet, but overall it was't so bad. I was really tired after we got because of all the walking, but I think it was a good kind of tired.

Here's a map of the route we took from Mills to the Park. Make sure you click on the icons because I've put pictures of me and my friends on them.


View Mills Creek Canyon Park in a larger map

I Propose We Burn Money! =]

Did you say burn money?! YUP! Here's how you do it...

Materials:
-dollar bill
-tongs
-water
-alcohol
-a lighter
-salt, or to color the flame: use Potassium Chloride for a purple flame, or Copper Chloride for a green flame

Procedure:
1. Make a solution with 50mL of water and 50mL of alcohol.
2. Mix in a pinch of salt or chemical of choice to color the flame.
3. Soak the dollar bill in the solution of water, alcohol, and salt until it is completely wet.
4. Use the tongs to hold the bill and move it away from the solution.
5. Light the dollar bill on fire; watch and wait until the fire burns out.

Safety Precautions:
-wear goggles, just in case!
-have an easy access to water near by in case you burn yourself.
-use tongs to prevent burning yourself
-have an adult near by if you are a minor.
-ask for help if needed.

The Science Behind It:
COMBUSTION!
C₂H₅OH + 4 O₂ -> 2 CO₂ + 3 H₂O + energy
The alcohol is what burns, instead of the dollar bill itself. The flame is also not hot enough to burn the water, since water has a high heat capacity. Therefore, since the water is not burned away, the dollar bill itself does not burn either. In the end, the flame burns out itself, leaving a damp dollar bill.

HAWAII!! :D

So over spring break I went to Hawaii! it was amazing!! it was my first time there and I had the best time! The weather was so warm, I wore shorts and a tank top all day; even when it rained it was still comfortable. The first three days I went to Oahu. The beaches were beautiful and I did a lot of shopping and walking around. I also went to Pearl Harbor and the Polynesian Cultural Center. At the PCC, there were simulations of the different Polynesian islands from Hawaii to Tonga. There was also a night show, exhibiting different types of traditional hula dances that were pretty cool. Then I went to Maui and Maui was just spectacular! We stayed at the Fairmont KeiLani. It was so nice, and the service and people were super friendly and all willing to help you. I went horseback riding and snorkeling...although I ended up getting seasick and threw up, so that kind of ruined the entire day for me. the food in Maui was delicious!! I also went to a luau which was super cool and there was the most beautiful sunset there! At the luau they cooked the kalua pig, which is the main course, in the ground for the whole day and when the luau started they dug it out of the ground and served it. Overall I thought the trip was great!! I can't wait to go back, and maybe I'll try the big island this time!

Introducing....David and Joan Webb!

Today we had guests speakers David and Joan Webb come to talk to us about vacuums and we did several interesting experiments. We learned about how pumps don't suck, instead, they create a low atmospheric pressure, which is the same as a vacuum. Because gas and fluids flow from high to low, we were able to do make wonderful and interesting experiments. We did one where we blew up a balloon so that it was really small, and then we put it in a container like thing, and began to use a pump to take away all the air inside the container. Soon, the balloon began expanding!! Even with the little knot on the end. It was so cool!

Another experiment was the feather and ginny experiment, where we demonstrated how a feather and a steel washer could fall at the same pace and hit the ground at the same time. It was able to do this in a vacuum because there was is no air resistance in a vacuum, therefore, allowing the feather to drop simultaneously with the washer.

The second to last experiment was really interesting, and I learned something I never knew before. We put a ringing door bell into the container and began to decrease the air pressure inside. Soon, we could no longer hear the bell chiming but we could see by a flashing light that the bell was still going. I soon learned that sound needs air to be able to be transmitted, and since we had taken away that air, we could not hear the sound. This also applies to space. Since space has no air, one cannot hear a spaceship explode; therefore in star wars, at then end where the enemy ship explodes, the film makers were wrong to add sound.

The last experiment we did was we boiled water to the point of freezing it...without fire or a match, just air pressure It was interesting because as the water was boiling, the water temperature kept decreasing, and that was because the boiling point in a vacuum or space is lower than in the regular atmosphere. At the end, we had a relatively solid piece of ice, it was amazing, I never thought you could do that! Overall, this was a wonderful experience, and it was cool being able to witness these amazing things, and actually being able to understand the full science behind it :)

first swimming meet!!

Yesterday was our first official swim meet of the season against Carlmont high school. I think i did considerably well individually. In the beginning, the coach kinda of switch our events a little bit, so I ended up doing the 200 free, which is 8 laps! I was so scared and nervous because the only time i've done that in a race was my first race freshman year, and I hated it so much! But, i actually got second so i was really happy. It meant I improved! And for butterfly, i was 0.3 sec away from first place!!! on the last 400 free rely, we were ahead but then we lost it in the middle, and we were third. I was anchor, which is the last person to go, and I really wanted to win, so I was able to swim past the second place girl and earned our rely team second place :D i think that was the highlight of the meet for me. I can't wait till next thur! I may complain a lot, but no matter what, I love swimming!

ohhh, and today is a half day!! so i get out of school at 12:30, but we have swim practice at 1:30 :[ oh well....

Three Day Weekend!!! :] plus heat transfer

So tomorrow we don't have have school because of staff recess, so that means no school Friday!!! The only thing is that I don't think im doing anything tomorrow, just homework...how boring. Oh well, anyways, so in chem we've been doing heat transfer and I get about half of the unit, and the test is Monday :[ The first half is using the equation Q=mc(delta T), which is how you can calculate the amount of energy an object has given off, this is calorimetry. We learned how to calculate the engery given off from the different stages of matter, liquid, solid, and gas. It's kind of interesting, and I like it because it's similar to stochiometry, in that you just plug in the numbers, so it's simple to understand. The second part of this unit is heat transfer the trying to figure out equilibrium. We are suppose to use Le Chatelier's Prinicple, which is: "if a system at equilibrium is disturbec, the system shifts to counter the effect of the disturbance." I kind of understand it, but it still confuses me when you have to determine the euqilibria if the pressure or temperature is increased or decreased. I guess I just have to play the chemistry games to study. I hope I can understand it in time for the test....

Swimming and elephant toothpaste

Swimming season hast started. I love it because it doesn't stress me out like basketball does (which, btw, we went undefeated, 10-0 :D) My favorite strokes are butterfly, then freestyle, then breaststroke, then backstroke. Swimming relaxes me, and I love the meets because its a lot of fun and there's always food there and its a lot of fun hanging out with you fellow team mates.

In Chemistry, we did a lab where we made elephant toothpaste. We mixed hydrogen peroxide with some liquid soap, then added a catalyst and poof, the yellow foam you see at the left erupted. Everyone was amazed and I thought it was really cool. The foam was hot and steamy and people began to play around with it. I wonder if they really brush an elephant's teeth with this....

Sf Chinese New year Parade

Yesterday was the San Francisco Chinese New Year Parade! I went as part of dragon team and it was so much fun. I have a lot of friends on the team so I got to hang out with them a little as well as create a lot of memories. It was really nice to hear the kids laughing on the streets and everyone seemed to enjoy the parade. It was really hot and we had to do a lot of running but it was worth hearing the joy around me and knowing what I was doing was bringing a lot of happiness to other people. After the parade the whole team went to Four Seas Restaurant to eat dinner. It just so happens my former classmate’s parents own the restaurant and she was there eating dinner with her family too since she was in the parade so it was cool to see my old friend again. The dinner was a lot of fun and I got to meet new people who sat at my table. It was nice too because they gave presents to all the people who headed the team like Mr. Philips, Mrs. Wu, and a lot of other important people who were involved, so it was very sentimental too. I really can’t wait for next year because next year I think I want to do music instead of the body. I’m glad I decided to join this year because now I have something to look forward to every year and since I know a lot of people in the group, this will create even more memories for me to look back upon.

homegoing rally!!!

Today was a really fun day. We had a double fourth schedule and homegoing rally. There were so many dancing groups. i think this was the best rally this year. From Team Rocket to Encore to Mills High's own dance class and cheer team, all the dances were really really cool. The teachers even did a dance to Michael Jackson's song, Beat It. There was a lot school spirit and the atmosphere in general was just awesome. The band played and the mascots were great, and the national anthem was sung by the lead actors of Mills High School's spring musical: Smile. I think my favorite part was watching the second generation of Supreme Soul on America's Best Crew: the Academy of villains. They pulled off some super cool dance moves and everyone was going crazy! Overall, i think today was pretty awesome. :)

Undefeated?

GUESS WHAT?! we might become the undefeated champions in our basketball league if we win our game against Burlingame High School (knock on wood). We have worked so hard for this! I can't believe this is our last game!! It's actually my last game on the Mills High School Girls JV team, so hopefully this will be a good one. I actually haven't been playing all that great, so hopefully i can step it up. My next sport is swimming, and im SUPER excited for that! I'm kind of scared because there's a new coach and they've been practicing for almost two weeks now, so hopefully i can make up the difference in my effort and hard work. Wish me luck tomorrow! :)

Stoichiometry

STOICHIOMETRY! I think this has definitely got to be the easiest unit we've done so far! It's basically balancing equations! the only thing you have to know is g X to mol X to mol Y to g Y. It's plugging in numbers and doing the calculations. I actually really enjoy this unit and hopefully, we'll get to do more of this. I already talked about the lab that accompanied this in my previous blog. Anyways, i was so excited about it, I finished 3 whole pages of stoichiometry problems in one day, and the packet is even due unitl next week! :D

Magnesium Oxide

wow i haven't blogged in few weeks! sorry! anyways, today we did this lab with magnesium oxide and it was pretty cool because we got to see real sparks fly and gas being burned and all that cool stuff. We had carefully measured out a specific amount of magnesium and put it into the bottom of a crucible. then we lit a flame and turned on the gas and cooked it until the magnesium oxidized. The way to check was to lift the lid of the crucible and if there was smoke coming out or the magnesium was brightly lit then that meant it wasn't done cooking. It was cool to see how bright the magnesium got just being exposed to the air for a few seconds. I think that was just the best part: seeing the reaction of the magnesium and the oxygen was cool enough :)

Chemistry! :]

So this week we did a lot of interesting labs involving bases and acids and trying to figure out the pH level of a certain solution. It was cool to see how ROY G. BIV applied to determining of what the pH was. Basically if the solution turned into any colors from red to yellow, it is an acid (pH 0-6). Colors green to purple meant the solution is basic (pH 8-14). Yellow usually is a neutral color, which means the pH level of that solution is 7. We also learned with litmus paper, if it was blue to red, its an acid, but if the color goes from red to blue, its a base-a-roo. ahhh! we have a test tomorrow!! The material is so confusing and i dont really understand the ionization stuff :[ I have to study tonight!!!

Like Dissolves Like

Dissolving means to mix two substances it together to create one solution. The solute combines with the solvent so the two substances become one (i.e. sugar and water)
There is a rule that goes along with this, and that is "like dissolves like":
"Like dissolves like" means that a solvent dissolves a solute with the same polarity; therefore a polar solvent will only dissolve with a polar solute and a non polar solvent will only dissolve with a non polar solute. In the example on the left, the oil and water do not dissolve because water is polar, but oil is non polar, therefore they will eventually separate even if you try and mix them.