Mini-Project #1: Make Invisible Ink

How to Make Invisible Ink
Chemical Properties of Lemon Juice


Materials:

Half a lemon

Water

Spoon

Bowl

Cotton Bud (Swab, Ball)

White Paper

Lamp or other light bulb

Procedure:

1. Squeeze some lemon juice into the bowl and add a few drops of water.
2. Mix the water and lemon juice with the spoon.
3. Dip the cotton bud into the mixture and write a message onto the white paper.
4. Wait for the juice to dry so it becomes completely invisible.
5. When you are ready to read your secret message, heat the paper by holding it close to a light bulb.

Safety Precautions:

Safety first, goggles on!
The acid from the lemon can burn your eyes.

Scientific Principles:
Since lemon juice is acidic and also organic, an oxidation reaction occurs when heat is applied and the words will turn brown. Any other acidic substances will work as well. Catherine and I used vinegar as a substitute.





PHOTOCREDIT: Marcia Lee

The project itself failed slightly, as we did not have a lightbulb to hold the paper to, so we attempted sticking it close to the fire. The vinegar began to oxidize slightly, but we did not dare sticking the paper any closer to the fire. By the way, the message reads "HI! WE LOVE CHEM!"

IProposeWe: Make Fireballs that are Cool Enough to Touch!

Links:
How to Make a Fireball
Step-by-Step Video Tutorial



Materials:

2" x 5" strip of cotton cloth

A cotton threaded needle

Lighter fluid (must be naphtha or kerosene)

Lighter or matches

There are two procedures to this experiment. First, the creation of the ball itself...

Procedure:
1. Thread the needle.
2. Fold the cotton strip into a ball and pierce it with the needle.
3. Wrap the thread around the ball. Pierce the ball one more time and break the thread.

And of the fireball:
1. Place the ball on a fire proof surface, such as a pan or our chemistry tables.
2. Soak the ball with lighter fluid, being careful to avoid hands or clothing.
3. Pick up the ball with tongs before putting it in your hand (to check if the ball is indeed too hot to touch, but it shouldn't).
4. Hold the ball while rotating it in your hand to avoid burning.
5. Put out the fireball when the cotton starts to become black and burn.
6. To blow out the fire, you need to blow on it hard or suppress the fire (by putting the lid on the frying pan, for example).

Safety Precautions:

Avoid synthetic material such as nylon. These will burn and melt.

Avoid holding the ball when the fire begins to consume the cotton or it will be too hot to hold.

Scientific Principles:
1. This is a reaction of combustion, meaning oxygen is a reactant (the air) and carbon dioxide and water are products.
2. This is an exothermic reaction. Energy, in the form of heat, is being released.

STP and Star Review (#12)

STP is not sexually transmitted pleasure.
In fact, it is the standard conditions for temperature and pressure. These conditions happen to be 0 degrees celsius (or 273 K) and 1 atm. 1 mol of any gas at STP has a volume of 22.4 Liters.

By the way, all gas temperatures must be in K (Kelvin).

0 K is absolute zero. You can't go any lower on the temperature scale. Absolute zero is centigrade is -273 C. (C = K - 273)

On a random note, Gay-Lussac discovered the law that as air pressure increases, so does temperature. Yesterday, we tried to find the molar mass of air. I guessed 29.92 g/mol. It actually came out to be approximately 30 g/mol. We figured this out by creating a vacuum in a test tube, measuring the mass of the vacuumed (evacuated) testtube and then when it was released.

I'll update this later!

Today's Guest Visitor

Today, in class, we had a great presentation by David Webb, a member of the American Vacuum Society. Wow, I had no idea such a society existed dedicated to researching the laws of physics, especially vacuums, where there is no sound. We performed a variety of experiments to further instigate our knowledge of vacuums. The first experiment we did is to figure out how much atmospheric pressure is applied to us at all times. Apparently, atmospheric pressure (at sea level) is 14.7 PSI. Whoo hoo. We held a heavy metal bar called the "Earth Bar" to show just how much pressure is being applied to us at all times.

We also used a pressure machine. Basically, it sucked all of the atmospheric air out of a canister. When you put a tied balloon in there, it got bigger. The same thing happened with marshmellows (but after withdrawing the marshmellows, they became shriveled up). Another interesting experiment proved that lack of air, or a vacuum, did not carry sounds. We put a dinging doorbell into the pressure machine, sucked out the air, and voila - the ringing stopped!

By the way, I found this column on vacuums quite interesting. I'm assuming you would probably feel the same. I also learned that something sticks to something, for example a suction cup on a shower glass door, works because of the atmospheric pressure pressing against the cup and creating a vacuum. The force of a vacuum is really strong. When you suck the air of something, it becomes very hard to open it.

Fun Fact: Toricelli, inventor of the mercury barometer, was one of the first inventors who sustained a vacuum.


The machine used looked something like pictured above, just simpler.

Gases and Back from Japantown!

On Monday, we started a new unit about gases. Gas molecules are always moving around; their molecules are the most spaced out apart (compared to liquid and solid). They have "kinetic" energy that goes up when temperature and speed go up. Gas pressure can be measured in a variety of units - mm/Hg, in/Hg, Torr, kPa, and atm. Gases are determined by pressure, volume, temperature, and number of particles. The combination gas law is P1V1 / T1 = P2V2 / T2.
It is a combination of Boyle's Law, Gay-Lussac's law, and Charles's Law.


Near absolute zero, a gas acts as a solid. Absolute zero for gases is 0 K or -273 degrees Celsius. However, temperatures for gases should be measured in Kelvin. There are also a variety of formulas to calculate the volume, pressure, or temperature of a gas. The following formulas, include ideal gas law, kinetic energy laws, and more.


Contrary to popular belief, there is no air in balloons that float. Instead, there is helium.


Ah, it feels so weird to be back from school after a long day of doing nothing...aka going to Japantown with my best friends from Japanese class. Yay! At Japantown, we went on a scavenger hunt about Japanese culture with an assigned group (Emily, Kristel, Elaiza, Rochelle, KT, Charles, and Bruce) Afterwards, we ate at Sapporo Ya. I had chicken teriyaki and ramen and tempura. And coke. MMMMM, yum. Most of my group were freshmen, who were eager to learn about Japanese culture and speak better 日本語。Nooo, I don't want to learn. xD LOL, some people ditched 7th I think. I'm not that bad. I'm eager to learn about chemistry!

MC Delta T

That's calorimetry dogg.
Calorimetry is the measurement of specific heat capacity.
Specific Heat Capacity is the amount of energy required to raise the temperature of 1 gram of a substance by 1 degrees celsius.
The specific heat capacity of water is 1 calorie per grams degree celsius.
and 1 cal is equivalent to 4.184 Joules.
Temperature and heat flow can be understood as the movement of molecules.

Whew, that was confusing.
By the way, calories are different from Calories. 1 Calorie is 1000 calories (cal).


These are some calorimetry problems (with their solutions) that we worked on.

Hmm, what else...?
During phase changes, energy is not required.
See how the line is straight in the following graph?

Homegoing! and Equilibrium

3/26/10

What is equilibrium? Basically, the forward rate of an equation is equal to the reverse rate. Equilibrium resists change. Molecules also need to overcome activation energy in order to start a reaction. Activation energy is the minimum amount of energy needed (in the collision) for a reaction to occur. Molecules react by colliding with sufficient energy and with proper orientation. Catalysts speed up chemical reaction, but they aren't consumed and don't mess up with equilibrium.



2/19/10

Today was the Homegoing Rally. :D Instead of electing princes and princesses, we elected teachers as the Homegoing King and Queen. Mr. Williams and Ms. Dove won! LOL. I voted for Mr. Williams and Mr. Olson. XDD

The Academy of Villains performed for us at the rally today. Compared to what I've seen, they were outstanding. Some of the guys did backflips and frontflips...and just amazing breakdancing moves. I don't even know how to describe them. But they were on America's Best Dance Crew. :D and they're going on America's Got Talent soon! LOL, since Krystina and I were sitting on the floor, they were hecka close to us. O_O We got a pretty good view. During the rest of the rally, our view was obstructed by some people's fatty legs. XD

The teacher's dancing was pretty funny too. That little kid was really cute! Who was he anyway? And the singers of the National Anthem were pretty creative and nice sounding as well!

MONDAY'S A HOLIDAY! <3333 AMERICA!
got to go, bell rang.