Mini-Project #3: Making Playdough

Sugars and Polysacharrides!
Components of Starch and other Saccharides

Materials:
- 2 Cups Flour
- 2 Cups Water
- 1 Cup Salt
- 2 Tablespoons Vegetable Oil
- Food coloring!

Procedure:
1. Mix all of the ingredients together, and stir over low heat.
2. When the dough pulls away from the sides and clumps in the center, remove the pan from heat and allow the dough to cool enough to handle.
3. Turn the dough out onto a clean counter or silicon mat, and knead vigorously until it becomes silky-smooth.
4. When you're done store it in an air-tight container.
5. If it begins to dry out, you can knead a bit of water in again to soften the dough back to usability.

Safety Precautions:
- Do not burn yourself on the hot pot.
- It is safe to eat this, but the taste will be unfavorable.

Scientific Principles:
1. Playdough is made out of starch, which is a polysaccharide.
2. Polymers are long molecules consisting of repeating structural units.

Mini Project #2: Rock Candy

In chemistry class, we made rock candy, also known as crystallized sucrose.

Materials:

Popsicle Stick

String

Lifesaver (to weigh the string down)

Glass Beaker

Pot with Saturated Sugar Water (1 cup water, 3 cups sucrose)

Instructions:

1. Tie your lifesaver onto a string, which should be the length of the glass beaker you are using.
2. The tie the string (and attached lifesaver) to a popsicle stick and place into the glass beaker. The string should hang about 1/2 - 1 inch off the bottom of the beaker and should be placed strategically in the middle, so it avoids touching the sides.



3. Boil a pot full of saturated sugar water.
4. Pour the hot solution into the the glass beaker.
5. Place the beaker in a place where it will be undisturbed. Crystals will form when the liquid cools down after a few days to a week.

* Crystals will not form on nylon string.




Safety Procedures

Use hot mitts to handle the pot full of boiling hot water!

Wear your goggles in case hot water splashes into your eye!

Do not use a wishing weight or anything metal to weigh down your string. This could be potentially toxic if you're going to eat your rock candy.

Scientific Principles
1. Crystallization:
Crystals are formed when a substance arranges itself in repetitive arrays. The supersaturated sugar solution contains more sugar than water. As the solution cools over days, the sugar forms as a precipitate on the string.

2. Evaporation:
Over time, the water molecules from the supersaturated sugar solution leaves the rock candy. The crystals thus grow molecule by molecule.

PHOTOCREDIT TO FIONA CHAN AND MARCIA LEE!

Chemistry Standard: Calorimetry

Chemical Thermodynamics
Students know how to solve problems involving heat flow and temperature changes, using known values of specific heat and latent heat of phase change.

Also known as...
CALORIMETRY

You can use a calorimeter to measure the heat quantity of a substance.


Or it can be defined with the infamous equation:
Q = MC∆T
M = Mass
C = Specific Heat Capacity
∆T = Change in Heat Temperature (Final temperature - initial temperature)

A useful constant for C would be the specific heat of water which is 1 cal/grams°C or 4.184 J/grams°C. Ice's specific heat capacity is .5 cal / grams°C and steam's specific heat capacity is 0.4 cal / grams°C.


Water, ice, and steam!

I will demonstrate how to solve for each of the variables (mass, specific heat capacity, and ∆T) in the following video. The step-by-step instructions are supplemented below.

Solving for Q:

A 21.0g sample of water is cooled from 34.0°C to 28.0°C. How many Joules of heat were removed from the water?



In order for calculate the values of ∆T, C, or M, you must use algebra to solve the equation for each of the variables.

I have solved the equations already!

M = Q / C∆T
∆T = Q / MC
C = Q /M∆T

Phase change problems (such as melting from a solid to a liquid) can be solved by using the same formula but by also using the extra formulas:

Q = ∆HVap = 540 cal
Q = ∆HFus = 80 cal

Trips to Mills Canyon

View Mills Canyon in a larger map

I did not embark on this wonderful, positively invigorating trip to view the best-kept secret of Burlingame, also known as MILLS CANYON! I was not too upset at missing at missing this opportunity, though. I see nature in its finest form quite often, actually, because 1) my cousin has a house in the wilderness of Santa Rosa and 2) I've walked on wild trails before. Therefore, going to Mills Canyon would have not been a new experience.

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!