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.