Lab 5B: sometimes it's CHEMISTRY

Hola to our fellow blog readers! As all of you already know, today is a lab day for us, and we're going to further explore the topic of chemical reactions in this blog (*cough cough* pull yourselves together girls, we're NOT going to make love potions or anything related to that) Instead, we'll be discussing about 7 different chemical reactions. They're not exactly as exciting as the methane-rocket we did the other day, but they're way better than the aluminum foil.

Now, may I ask all of you to put on your safety goggles and lab coats, we're about to start our experiments!

Reaction 1:Burning Copper

For our first experiment, we're going to burn a piece of copper wire under a flame. First, turn on the Bunsen burner and adjust the flame to high heat (blue color), then hold the wire over the flame, with a pair or tongs, of course! (Do not try to hold it with your hands...or you'll have an extra dish for your lunch....)

Now, observe as the copper is burning. The blue flame has turned into green color, while the wire has turned to brown-ish-black. This is a simple synthesis reaction between copper and oxygen in the air. The chemical equation can be written as the following:

4Cu + 1O₂ → 2Cu₂O

Reaction 2: Rusting Iron Nail

Time to move on to our next experiment! Now we're going to rust a piece of iron nail. First, we need to clean the nail with a piece of steel wool and make sure its surface is shiny. Then, prepare some copper(II) sulfate in a test tube which half covers the nail we put in. Copper sulfate is a blue colored salt that is mostly used as a fungicide, which is, to kill fungi, spores, and mushrooms. The chemical reaction is a single replacement, where the iron has combined with sulfate, forming sheets of coating.

1Fe + 1CuSO4 → 1FeSO4 + 1Cu

Reaction 3 and 4: Dehydrating a hydrate

Our third experiment will be removing water from copper(II) sulfate pentahydrate by burning this solid over a flame. (Hmm..."dehydrating a hydrate"...don't you like the oxymoron?) As you recall what we did before in Lab4C, a hydrate is a compound that contains water molecules. When it is heated, it'll give off water, leaving the anhydrous salt behind. 

During heating, the hydrate will turn green gradually, and then completely white. If we add several drops of water to the anhydrous salt, it'll turn back to it's originally state as a blue-colored hydrate.

This is a decomposition reaction.

1CuSO4‧5H2O → 1CuSO4 + 5H2O

Reaction 5: Forming Precipitate

Calcium chloride is a salt which is widely used as brine to prevent roads from freezing, treating hypocalcaemia patients, or even flavoring pickles. Sodium carbonate, on the other hand, is mostly used in manufacturing glass. These solutions both have a clear color when dissolved in water, so be careful and do not mistaken them as water, they are not good for your health. Now back to our experiment, mixing these solutions together and you'll get a precipitate forming, it is a double replacement reaction.

1CaCl2 + 1Na2CO3 → 1CaCO3 + 2NaCl

Reaction 6: Dissolving Zinc

Now, moving on to our next task. This time, we'll use hydrochloric acid to cover a piece of mossy zinc in a test tube. As the acid is dissolving the metal, we'll see  lots of bubbling, and it also gives off heat! This is an example of a single replacement reaction.

1Zn + 2 HCl  →  1ZnCl2 + 1H2 + Heat

Reaction 7: The Ultimate Classic

Here's our LAST experiment for the day; and the last one is always the best. 

We're going to pour hydrogen peroxide solution into a test tube, and then add a bunch pinch of manganese(IV) oxide into the solution. In this case, manganese oxide acts as a catalyst to help decomposing hydrogen peroxide into water and oxygen. In order to test this theory, we put a burning glowing splint into the test tube while it's releasing O2 gas. The splint will then grow into a larger flame when it is in contact with oxygen gas.

2 H2O2 → 1O2 + 2 H2O

So this pretty wraps up our lab for today, you guys can put clean up all your equipments now, and don't forget to wash your hands before going. Also, remember to study for the fiesta (aka: quiz) on Monday! Mr(or Mrs)PinchOfKCN will always be proud of you!

Oh, and one LAST thing before we end this lesson, here's a combustion reaction between methanol and oxygen experiment performed under safety guidelines, so do not try to do this experiment at home :)

And here's something unrelated to chemistry but interesting enough to caught your final attention: calculating the acceleration and velocity of this methanol-rocket! But just so you know Mr. PinchOfKCN's physics skills are not as awesome as those at chemistry, so please excuse me if I made any mistakes....
(The datas used in the calculations are approximate estimations, so the answers are possibly, flawed.)

time in air = 0.23s
initial velocity = 0m/s
mass of empty bottle = 1.8kg (according to a standard 5 gallon-bottle)
inclined plane angle = ~35°(okay, I REALLY took a guess)

For finding acceleration, we use the following equation:

a = g x sinΘ

Therefore = 9.8m/s (sin35°) = 5.6m/s/s

Finding how much force has been applied to the rocket:

Fa = m(a+gsinΘ)

Therefore = 1.8kg (5.6m/s/s + 9.8m/s/s x sin35°) = 20N
So the basic force that's required to shoot this rocket is 20 newtons. If an idiot was standing in front of the rocket when it is about to launch, he'll definitely gets hit in his face, right? The calculation below'll show you how much it hurts.

mass of object in motion = Fa / a

Therefore = 20N / 5.6m/s/s = 3.6kg
When an object is moving, the faster it moves, the "heavier" it gets. This 1.8kg water bottle has gained an extra 1.8kg while it's moving! Imagine the idiot gets hit by half a bag of rice...Ouchhhh!!!