Chem Mini Project 3: Making my own rock candy!!

I don't have to buy rock candy from stores anymore! Since I now know how to make my own rock candy. :)


Materials:

• 1 cup of water
• 3 cups of table sugar or sucrose
• a clean glass jar
• a pencil or a Popsicle stick
• string
• a pan or bowl for boiling water and making solution
• spoon or stirring rod
• a hot plate
• a lifesaver hard candy

How I Made It:

1. Mix the sugar and water together.
   
2. Then put it on a hot plate and turn it on high until the sugar is dissolved into the water.
3. Next, tie the string to the Popsicle stick and the other end of the string through the hole of the lifesaver candy and tie a knot.
4. Pour water onto the hanging string and cover the string with sugar.
5. Pour the sugar water mixture into the small jar.
6. Balance the Popsicle stick on top of the jar and leave the lifesaver candy hanging so that it does not touch the bottom of the jar.
7. Place it somewhere safe and come back after 3-7 days to see the formation of crystals!

Science:
Since water is the universal solvent, many substances can dissolve in it, including sugar. However, at a certain point, a substance cannot dissolve anymore and that is when we know that the solution is saturated. When we heated the water and sugar, we increased the saturation capacity, making it possible for more sugar to dissolve because heat causes molecules to move apart and have more energy.

When we cool the water down, the solution becomes supersaturated, having too much sugar. Since we placed the string in a supersaturated solution, the sugar will be attracted the the already-existing solid molecules stuck to the string, therefore creating crystals. As time passes by, the water will evaporate while the sugar remains in the solution. Because it will become more saturated, more sugar will be added and our crystal will grow bigger and bigger.


Photocredit to Erica Sue 5th period:

Mini Blogpost 2: Dancing Raisins!

Today, I made raisins dance in a cup full of soda.

Materials I used:

• a tall, clear glass or plastic cup
• a few raisins
• a can of clear, colorless soda like 7-up or Sprite
  

Procedure:

1. Pour the can of soda into the clear cup. Watch how the carbon dioxide gas (bubbles) are released from the liquid.
2. Then, drop 6 or 7 raisins into the cup.
3. Watch what happens to the raisins.

Observation: The raisins all sink to the bottom at first but then one by one, they quickly ascend to the top and then just as quickly, they sink to the bottom again.

Science: At first, the raisins sink to the bottom of the cup because raisins are more dense than the liquid. Since it is a carbonated drink, releases bubbles or carbon dioxide. When the raisins stick to some of the bubbles, the raisin starts to float up to the top because of the increase in buoyancy. However, when the raisin reaches the top, the bubbles pop and are released into the air. Since the buoyancy is decreased, the raisin sinks to the bottom again. The raisins float and sink until most of the carbon dioxide gas is gone into the air. As time passes, the raisin gets too heavy to float to the surface.

Chem Standard Blogpost :O

ChemStd 7d: Problems about heat flow involving temperature changes can be solved by using known values of specific heat and latent heat of phase change.

Heat is the energy transferred from one object to another because of a difference in temperature.

No Phase Change Problems:

To solve these kinds of problems, use the equation Q= mcΔT.
m= mass of the matter being measured. (g)
c= specific heat, the amount of heat energy required to raise 1g of a substance 1°C. (cal/g°C) or (J/g°C)
ΔT= change in temperature, the increase or decrease in the temperature of the matter (°C), = final temperature - initial temperature

Q= mcΔT must refer to only ONE object. Mixing your references will result in a wrong answer.

The value of Specific Heat is not the same for all types of matter. Heat affects the temperature of those things with a high specific heat much less than those with a low specific heat. Water has the highest specific heat while metals have low specific heats so a small amount of energy raises the temperature of metals a lot.

Here are Specific Heat Capacities of some common substances:



Water (liquid) - 4.184 J/g°C
Water (ice) - 2.03 J/g°C
Water (steam) - 2.0 J/g°C

To convert to J/g°C, use the Calorie-Joule Conversion: 1 cal = 4.184 J.

For example:

A block of lead having a mass of 20.0 grams is heated from a room temperature of 22.4 ^oC to a temperature of 85.4 ^oC. What would be the added heat to the lead?


From:

http://www.neoam.cc.ok.us/~rjones/Pages/online1014/physics/chapter4/pages/heat.html

1. Write the formula
2. Substitute the variables
3. Simplify the equation and cancel the units.
   
4. Calculate the answer
5. Box your answer and don't forget to include the units!
   

You can also find the value of the other variables by rearranging the equation:

m= Q/cΔT

c= Q/mΔT

ΔT= Q/mc


Latent Heat of Phase Change Problems:

Heat of Fusion - ( ΔHfus) - the heat absorbed by a substance that is melting from a solid state to a liquid state at a constant temperature.

Heat of Solidification - (ΔHsolid) - the heat lost when a liquid changes to a solid at a constant temperature.

Heat of vaporization - (ΔHvap) - the heat absorbed by a substance that is vaporizing from a liquid state to a gaseous state at a constant temperature.

Heat of condensation- (ΔHcon) - the heat lost when a gas changes to a liquid at a constant temperature.

Energy is conserved in all physical and chemical changes:
ΔHfus = -ΔHsolid
ΔHvap = -ΔHcon


Changes of State for Water:
Melting: ΔHfus= 80 cal/g
Solidifiction: ΔHsolid = -80 cal/g
Vaporization: ΔHvap = 540 cal/g
Condensation: ΔHcon = -540 cal/g

To solve phase change problems, use the latent heat of fusion or latent heat of vaporization formulas:

For freezing or melting, use:
Latent Heat of Fusion of Water: Q= mΔHfus
ΔHfus(H2O)= 80 cal/g = 334 J/g

For boiling or condensation, use:
Latent Heat of Vaporization: Q= mΔHvap
ΔHvap(H2O) = 540 cal/g = 2260 J/g

For example:
How many calories are needed to melt 225 g of ice at 0°C to liquid at 0°C?

Step 1: Write the formula
Step 2: Substitute the variables and cancel units.
Step 3: Calculate and box the answer. Don't forget to include the units.

Mills Canyon Park Field Trip :)

Our chemistry class went on a field trip to Mills Canyon Park! I thought I needed some relaxing time so i decided to go on that field trip. However, I thought it was going to be cold there so I wore layers to the hike. But instead of it being windy and cold, it was very very hot there! I was also carrying a very heavy backpack there. So I think I would've enjoyed it more if i had worn less layers and had carried a lighter bag. But I still thought it was really relaxing. I also liked looking at the scenery and observing nature.

Here is a map of the park:


View Mills Canyon in a larger map