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!