Wednesday, 28 May 2014

Magic Glass (Make it invisible)!


EQUIPMENT:
  1. Small object made with transparent glass (Such as marble, microscope slide etc.)
  1. A glass jar or container large enough to hold the small glass object.
  1. Clear water
  1. Vegetable oil


INSTRUCTIONS:
  1. At first, place the small glass object in the large glass container.
  1. Then put some clear water inside the bowl and submerge the glass object as much as possible.
  1. After that you can record how the small object looks like underwater.
  1. Now empty the water.
  1. Then put some vegetable oil into the bowl and again submerge the object as much as possible.
  1. Then you can record how the glass object looks like again if you wish.


RESULT:
  1. Underwater, the small glass object might look a bit distorted.
  2. Under oil the glass object should be invisible partially or completely.

EXPLANATIONS:

The object underwater look a bit distorted although it don’t change physically. The reason for this is because of the way light acts when it passes from water to air. Rays of light have 2 options when they pass from air to another transparent medium or material. One option is that, they can be reflected. This means the light rays are bounced back. Another option is being refracted. This means that, the light rays will continue to travel through the medium, but they will be a bit displaced from their initial path, will make an angel and bend towards a new path. We can see objects made with transparent materials such as glass because they reflect and refracts light rays. When a light ray pass from one medium to another medium, it changes its speed or velocity. Actually the difference in velocity among mediums determines how much refraction and reflection will occur. The smaller the difference in velocity, the less refraction and reflection. The larger the difference in velocity, the more refraction and reflection. Every medium has its own index of refraction. This is a measurement which indicates how light slows down when it passes the medium.
The index of refraction or air is usually considered to be one. This means that the light does not change speed when it travels through the air.
Although in reality light can travel at full speed only in a vacuum. But that’s completely another story so we won’t go there right now.
Now back to the discussion. When the index of refraction of a medium is greater than 1, the velocity of light in that medium will be lower than velocity of light in the air. In water, the index of refraction is 1.33, which means when light passes from air to water, it slows down.

Vegetable oil especially a specific brand called Wesson oil and glass  especially Pyrex glass have similar indices of refraction which is approximately 1.47. Light going through oil (especially Wesson oil) and glass (especially Pyrex glass) will experience minimal refraction and reflection coz the indices of reaction are similar to each other.

MORE EXPLANATIONS:

Light rays flows within different medium at different speed or velocity. Different medium resist the flow of light with different strengths. The characteristic that describes this property of a specific medium is called its refractive index or index of refraction.

Although oil (especially Wesson oil) and glass (especially Pyrex glass) have similar indices of refraction, the small transparent glass object will not vanish completely. It’s because the shape of an object effects the way light bends as it travels through. Another fact is, any impurities in the glass or oil will also change the index of refraction. The most glass object we will use in this experiment, submersion in the oil will produce a ghostly image of that glass object.

MORE EXPERIMENTS FOR YOU:
  1. Use vinegar instead of oil.
  2. Use glycerin instead of oil.
  3. Use different kinds of oil such as body massage oil, machine oil etc.

Saturday, 10 May 2014

Make Some RUST!


EQUIPMENT:
  1. A clean steel wool
  2. Tap water
  3. Vinegar
  4. Salt water
  5. Three paper cups

INSTRUCTIONS:
  1. At first cut out the steel wool into three pieces.
  2. Then place each piece in a paper cup.
  3. Fill one cup with enough tap water to submerge the piece of steel wool.
  4. Then fill the 2nd cup with salt water to submerge another piece of steel wool.
  5. Again fill the last cup with enough vinegar to submerge the piece of steel wool.
  6. Examine the three submerged pieces of steel wools after fifteen minutes.
  7. Record any kind of changes.
  8. Examine the pieces of steel woo after 2 hours.
  9. Record if there is any change.
  10. Examine the pieces of steel wool once a day for about 3 or 4 days.
  11. Record any kind of change you observe.

RESULTS:
  1. A brown layer of rust is developed on all the pieces of steel wool over time.
  2. The piece of steel wool which was in the vinegar starts to show signs of rusting almost immediately.
  3. The steel wool piece that was in the salted water shows signs of rusting within a couple of hours.
  4. The steel wool piece that was in the tap water starts to rust in about 3 days.

EXPLANATION:

Steel wool is made of iron. When iron reacts with the oxygen in the air a substance called iron oxide is created. It’s commonly known a rust.
The reaction is :

Rust form through Chemical Reaction

For the reaction to happen, some of the iron metal becomes iron ions in a process called ionization. Ions are electrically charged atoms which have changed chemically to either loose or gain electron. Iron metal can slowly ionize in the water. That’s why wet iron rusts. The iron ions can react with the oxygen dissolved in the water to create iron oxide. However, in salt or acidic solutions, the ionization process is a lot quicker.
In this experiment naturally the salted water is a salted solution. The presence of salt in the water boosts up the ionization process of the iron enough to make the rust visible within a couple of hours or a bit more. However, the vinegar is way better at ionizing iron. Vinegar is actually acetic acid. It can make iron oxide appear on iron within a few minutes.

MORE EXPLANATION:

The chemical reaction which causes the rust to form on iron is actually a type of corrosion. It’s the equivalent of the chemical reaction that causes green layer to appear on American pennies or copper. (To know more about this, you can read the experiment Make your coins green!) The only difference is that while pennies corrode and copper oxide is formed, the layer of copper oxide actually protects the metal underneath. But on the other hand, iron oxide destroys iron metal over time and make it fragile and useless.

MORE EXPERIMENTS FOR YOU:
  1. Use other kinds of acids to see and compare the effect.
  2. Use sugar water to see the effect!
  3. Can the rust be dissolved using other kinds of acids?

Tuesday, 6 May 2014

Magic Wool!



EQUIPMENT:

  1. A yarn of white wool
  2. Rubber gloves
  3. Metal washer
  4. A large cardboard box
  5. Two transparent drinking glasses
  6. Methyl salicylate (Can be found in science supply store or chemical shop)
[Warning – Be careful while handling methyl salicylate because direct contact can be harmful]

INSTRUCTIONS:

  1. At first wrap the white wool around the metal washer until it’s completely hidden by the wool.
  2. Leave at least ten inches of wool hanging off one end to make it easier to move the metal washer.
  3. Now place both transparent drinking glasses inside the large cardboard box so that if anything spills from the glasses the box can contain that.
  4. Pour about an inch of methyl salicylate into one of the transparent glasses wearing rubber gloves.
  5. Then hang the wool-wrapped metal washer into the methyl salicylate still wearing rubber gloves.
  6. Now wait for the wool to soak the methyl salicylate.
  7. After that carefully remove the wool-wrapped metal washer from the methyl salicylate and place it in the 2nd transparent drinking glass. Record its appearance if you wish.
  8. Now let the wool dry. Then you can record the changes if you wish.

RESULT:

  1. When fully soaked with methyl salicylate, the yarn of wool should look glassy and transparent. The metal washer should be visible through the yarn!
  2. When the methyl salicylate drains from the yarn of wool, it becomes normally visible once again.

EXPLANATION:

The experiment shows that, how the index of refraction of a material can be changed when it interacts with another different material. In our experiment, soaking the yarn of wool with the methyl salicylate gives the solid wool the same index of refraction as the liquid methyl salicylate. This makes the wool fibers appear to disappear.
As the methyl salicylate drains out of the yarn of wool, the index of refraction of the wool alters back to its original form. When the index of refraction do not match, the two different materials are visually distinguishable.


MORE EXPLANATION:

Light rays flows within different medium at different speed or velocity. Different medium resist the flow of light with different strengths. The characteristic that describes this property of a specific medium is called its refractive index or index of refraction.



OTHER EXPERIMENTS FOR YOU:
  1. Use nylon fiber instead of wool.
  2. Use polyester fiber instead of wool.  
  3. Use different other kinds of fibers.

Other Interests!