Sunday, July 12, 2009

Homemade lava lamp using simple materials

Using simple materials is possible make a lava lamp as shown above.
The water is more dense than the vegetable oil, so it sink. When the seltzer tablet is added the gás liberated makes the water float.

Running Pepper: a miracle of surface tension

Here we have another example of science experiments that uses surface tension to works.
Spread peppers in a plate full of water as the video above shows, then put a drop of liquid soap on your finger and put the finger in the middle of the plate to make the peppers run away.
In the post "How many pins is possible to put in a glass full of water" we explain what is surface tension, the soap will reduce the surface tension (the attractive force between the molecules of surface) and the water will run and carry the peppers with it.

Science Experiments: Magic soap bubbles

Baking soda and vinegar are very useful in science experiments, here we have another example in which this materials are used to amaze the people!
Put some vinegar in a aquarium, latter put some baking soda. The result of reaction is sodium acetate and carbon dioxide.
The CO2 is more dense than the air, so a soap bubble will float on it as a boat float on water. The buoyancy force is equal the weight of the bubble, thus we have the equilibrium and the bubble remains on interface CO2 / Air

How many pins is possible to put in a glass completely full of water?

As you can see in the video above, the answer is a lot! The is possible thanks a property called surface tension. The liquid’s surface molecules attract each other forming drops or the spherical layer over the glass formed by the volume occupied by pins.
This property of liquids allows small insects literally walk over the water without sink!
See more on Wikipedia

Slow motion rubber band trick

Put a rubber band in front of a TV screen to see it vibrating in a slow motion. Actually the vibration remain the same but we have the sensation that it slow down. This phenomenon is possible just because the frequency of rubber band's vibration is near the vertical frequency of screen.
The TV screen works as a stroboscopic light and it will not works in front of LCD screen.

Amazing science experiment: “nothing” put the candles out

What this video shows seems a magic trick but is pure science!
Baking soda (sodium bicarbonate) when is mixed up with vinegar (acetic acid) produces a gas called carbon dioxide. This gas fill the space around the candle flame and put it out because there is no oxygen, essential to combustion.
Some fire extinguishers use this kind of gas.

Build a little hot air balloon: the tea bag experiment

Using a simple tea bag is possible make a little hot air balloon, see the video instructions.
The fire heat the air inside the balloon, hot air is less dense than cold air, result: a buoyancy force greater than the weight will make the balloon fly.

Reaction between sugar and concentrated sulfuric acid produces coal

The concentrated sulfuric acid can take the water out of the sugar molecule producing coal plus water according to reaction equation:
C12H22O11(s) → 12 C(s) + 11 H2O(aq)
That is a exothermic process and liberates poison's vapors, then take care and use one appropriated place , don’t do it indoors!

Classic Science Experiments: Egg in a Bottle

Classic Science Experiments: Egg in a Bottle
You will need: a egg, an empty milk bottle and some matches

The match warm the air inside the bottle
the air become less dense and go out. Since the egg close the bottle, the air inside cool and the inner pressure reduce. Thus the atmosphere pressure push the egg.

Homemade Small Robot

Using a tooth brush and a old cell phone engine you can built a small robot.
The eccentric axis generates the vibrations that keep the robot running.
Is also possible use a electric engine normally found in toys and a large brush.
For more instructions see:

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