AKU

Aku bukan seorang penulis,
karena aku tak dapat menulis,
Aku bukan penyair,
karena akay tidak dapat menyair,
aku bukan pelukis,
karena aku tak dapat melukis,

Tapi.....

Aku Hanyalah seorang Pemimpi,
yang Yakin suatu Saat Nanti yakin akan menjadi yang berarti

Gold and Silver Pennies Fun Chemistry Project

All you need are a couple of common chemicals to turn your normal copper-colored pennies (or other mainly-copper object) from copper to silver and then to gold. No, the coins won't really be silver or gold. The actual metal involved is zinc. This project is easy to do. While I don't recommend it for very young kids, I'd consider it appropriate for kids ages third grade and older, with adult supervision.

Materials Needed for this Project

• clean pennies
• zinc metal (preferably powder)
• sodium hydroxide or sodium hydroxide solution
• tweezers or tongs
• container of water
• source of heat/flame

Note: Supposedly you can substitute galvanized nails for the zinc and Drano™ for the sodium hydroxide, but I was unable to get this project to work using nails and drain cleaner.

How to Make Silver Pennies

1. Pour a spoonful of zinc (1-2 grams) into a small beaker or evaporating dish containing water.
2. Add a small quantity of sodium hydroxide.
3. Alternatively, you could add zinc to a 3M NaOH solution.
4. Heat the mixture to near-boiling, then remove it from heat.
5. Add clean pennies to the solution, spacing them so that they are not touching each other.
6. Wait 5-10 minutes for them to turn silver, then use tongs to remove the pennies from the solution.
7. Rinse the pennies in water, then set them on a towel to dry.
8. You can examine the pennies once you have rinsed them.

This chemical reaction plates the copper in the penny with zinc. This is called galvanization. The zinc reacts with the hot sodium hydroxide solution to form soluble sodium zincate, Na₂ZnO₂, which is converted to metallic zinc when it touches the surface of the penny.

How to Make the Silver Pennies turn Gold

1. Grasp a silver penny with tongs.
2. Gently heat the penny in the outer (cool) part of a burner flame or with a lighter or candle (or even set it on a hotplate).
3. Remove the penny from heat as soon as it changes color.
4. Rinse the gold penny under water to cool it.

Heating the penny fuses the zinc and copper to form an alloy called brass. Brass is a homogeneous metal that varies from 60-82% Cu and from 18-40% Zn. Brass has a relatively low melting point, so the coating can be destroyed by heating the penny for too long.

Safety Information

Please use proper safety precautions. Sodium hydroxide is caustic. I recommend conducting this project under a fume hood or outdoors. Wear gloves and protective eyewear to prevent getting splashed by the sodium hydroxide solution.

source : http://chemistry.about.com

Science Magic Trick - Introduction to Floating Metal

Science Magic Trick - Introduction to Floating Metal

Can one float metal, for example, a paper clip, on water? In this science magic trick, you’ll learn how. Making a paper clip float on water may look like magic, but it’s all science - yet another in our series of science magic tricks.

Effect:
You make a metal paper clip float on water. (Really!)

The Science Secret:
The secret involves the water’s surface tension, the tendency for water molecules on the surface to be attracted to each other. This is the reason why when a glass of water is filled to the brim and small objects are added, you can see the water bowing up over the glass. And it’s also the reason why small insects and such can rest on the surface of still water.

The trick involves not break the water’s surface tension when resting an object, in this case, a metal paper clip, on the water’s surface.

Materials:
A glass or bowl of water
Two metal paperclips

source : http://magic.about.com

Egg in a Bottle Demonstration The Power of Air Pressure

The egg in a bottle demonstration is an easy chemistry or physicsdemonstration you can do at home or in the lab. You set an egg on top of a bottle (as pictured). You change the temperature of the air inside the container either by dropping a piece of burning paper into the bottle or by directly heating/cooling the bottle. Air pushes the egg into the bottle.

Egg in a Bottle Materials

• peeled hard-boiled egg (or soft-boiled, if a yolk mess interests you)
• flask or jar with opening slightly smaller than the diameter of the egg
• paper/lighter or very hot water or very cold liquid

In a chemistry lab, this demonstration is most commonly performed using a 250-ml flask and a medium or large egg. If you are trying this demonstration at home, you can use a glass apple juice bottle. I used a Sobe™ soft drink bottle. If you use too large of an egg, it will get sucked into the bottle, but stuck (resulting in a gooey mess if the egg was soft-boiled). I recommend a medium egg for the Sobe™ bottle. An extra-large egg gets wedged in the bottle.

Perform the Demonstration

• Method 1: Set a piece of paper on fire and drop it into the bottle. Set the egg on top of the bottle (small side pointed downward). When the flame goes out, the egg will get pushed into the bottle.
• Method 2: Set the egg on the bottle. Run the bottle under very hot tap water. Warmed air will escape around the egg. Set the bottle on the counter. As it cools, the egg will be pushed into the bottle.
• Method 3: Set the egg on the bottle. Immerse the bottle in a very cold liquid. I have heard of this being done using liquid nitrogen, but that sounds dangerous (could shatter the glass). I recommend trying ice water. The egg is pushed in as the air inside the bottle is chilled.

How It Works

If you just set the egg on the bottle, its diameter is too large for it to slip inside. The pressure of the air inside and outside of the bottle is the same, so the only force that would cause the egg to enter the bottle is gravity. Gravity isn't sufficient to pull the egg inside the bottle.

When you change the temperature of the air inside the bottle, you change the pressure of the air inside the bottle. If you have a constant volume of air and heat it, the pressure of the air increases. If you cool the air, the pressure decreases. If you can lower the pressure inside the bottle enough, the air pressure outside the bottle will push the egg into the container.

It's easy to see how the pressure changes when you chill the bottle, but why is the egg pushed into the bottle when heat is applied? When you drop burning paper into the bottle, the paper will burn until the oxygen is consumed (or the paper is consumed, whichever comes first). Combustion heats the air in the bottle, increasing the air pressure. The heated air pushes the egg out of the way, making it appear to jump on the mouth of the bottle. As the air cools, the egg settles down and seals the mouth of the bottle. Now there is less air in the bottle than when you started, so it exerts less pressure. When the temperature inside and outside the bottle is the same, there is enough positive pressure outside the bottle to push the egg inside.

Heating the bottle produces the same result (and may be easier to do if you can't keep the paper burning long enough to put the egg on the bottle). The bottle and the air are heated. Hot air escapes from the bottle until the pressure both inside and outside the bottle is the same. As the bottle and air inside continue to cool, a pressure gradient builds, so the egg is pushed into the bottle.

How to Get the Egg Out

You can get the egg out by increasing the pressure inside the bottle so that it is higher than the pressure of the air outside of the bottle. Roll the egg around so it is situated with the small end resting in the mouth of the bottle. Tilt the bottle just enough so you can blow air inside the bottle. Roll the egg over the opening before you take your mouth away. Hold the bottle upside down and watch the egg 'fall' out of the bottle. Alternatively, you can apply negative pressure to the bottle by sucking the air out, but then you risk choking on an egg, so that's not a good plan.