Why white shirt then to fluorescence when under UV light

I think most of you have ever been into dark room that contain UV lamp and you notice those white colour T-shirt will fluorescence. This is because modern detergents contain phosphors which convert UV light into white light. So when you wear your T-shirt under the sunlight your T-shirt will looks whiter than white which seem that your T-shirt looks clean. As the phosphor will convert the UV light from the sun to emit white light.

So next time you can try buying 2 brand new T-shirt, one washed it with detergent contain phosphor another just leave it unwash. Then put both T-shirt in a dark room with UV lamp, you will notice the T-shirt that has been washed will glow better than the one which is unwash.

How fluorescence light work

Hi, so long have not update my blog. Maybe I did not encounter any special science expt which I can write on. Finally, today I encounter one. My lab have a fluorescence light which half of it is with the white coating while another half is without the white coating. My previous lab tech have ever shown me that when that lamp is lighted up the part without the coating will not have white light. I did not bother to find out why that time but now I have to teach my new lab tech so I went to check out what is the theory behind it.

The fluorescent lamp is a sealed glass tube. The tube contains a small bit of mercury and an inert gas, typically argon, kept under very low pressure. The tube has two electrodes, one at each end, which are wired to an electrical circuit.

When the lamp is on, the current flows through the electrical circuit to the electrodes. There is a considerable voltage across the electrodes, so electrons will migrate through the gas from one end of the tube to the other. This energy changes some of the mercury in the tube from a liquid to a gas. As electrons and charged atoms move through the tube, some of them will collide with the gaseous mercury atoms. These collisions excite the atoms, bumping electrons up to higher energy levels. When the electrons return to their original energy level, they release light photons in the ultraviolet wavelength range.

As our eye cannot register ultraviolet photons, these light photons have to be converted into visible light with the help of phosphor which is the coating surrounded the tube. Phosphors are substances that give off light when they are exposed to light. When a photon hits a phosphor atom, one of the phosphor's electrons jumps to a higher energy level and the atom heats up. When the electron falls back to its normal level, it releases energy in the form of another photon. This photon has less energy than the original photon, because some energy was lost as heat. In a fluorescent lamp, the emitted light is in the visible spectrum -- the phosphor gives off white light we can see.

This is the reason why the part without the phosphor coating will not light up, as we cannot see UV light. Therefore it is also quite dangerous to look at that lamp as it is different from those UV lamp (black light). Those UV lamp have a black coating which is make up of different type of phoshor coating which absorb the harmful UVB, UVC and visible light but emitting benign long-wave UVA light with some blue and violet light. Whereas my lamp without any coating are emitting all UVA and harmful UVB and UVC.

Dancing Raisin

Hmm you like rum and raisin? Then have you tried 7up with raisin? Have you wonder why your raisin will "dance" in your 7up? It will flow up and down right? The theory is very simple, this is because the gas in the soft drink pushes the raisin up and when the gas bubbles pops, it will not be able to hold on to the raisin and the raisin will drop down.

It is best if you can get raisin that is very dry as the drier the raisin, the raisin will be more wrinkled and light so as to create more surface area for the gas bubbles to push the raisin up.

Alternatively if you do not have soft drink at home, you can try to put 2 teaspoons of baking soda in around 100ml of water, dropped your raisin inside and then add some vinegar into it. Effervescence will be observed once vinegar is added as vinegar which is an acid will produce cardon dioxide when react with carbonate. This carbon dioxide gas will forms into bubbles and pushes the raisin up.

So have fun and take a look at the video which I took myself that shows the raisin moving up and down.

Fire piston

Hmm, is so fun to play with this device known as fire piston. However you need a great strength to push the piston in order for the cotton wool (or any combustible material) to ignite. Above is the video of fire piston.

A fire piston is a device of ancient origin which is used to kindle fire. It consists of a hollow cylinder ranged in size from around 7.5 cm to 15 cm long, sealed at one end and open at the other. A piston which is about 1-2cm in diameter, can slide into the cylinder forming an airtight seal with the cylinder wall. The piston has a handle on the end to allow a firm grip to be applied to it and can be completely withdrawn from the cylinder.

The piston must be rammed quickly into the sealed cylinder with a single stroke. The compression of the air causes the temperature to rise rapidly to 260 degrees Celsius. This is hot enough for the cotton wool inside the piston to ignite. It can then be withdrawn and transferred to a larger mass of kindling to create a fire.

The principle of fire piston works based on rapid compression of the air (known as adiabatic compression) increases its pressure and its temperature at the same time. If this compression is done too slowly the heat will leak away to the surroundings as the gas returns to equilibrium with them. If the compression is done quickly enough then there is no time for equilibrium to be achieved and the absolute temperature of the air can suddenly become several times that of its surroundings, increasing the original room temperature of the air to a temperature hot enough to set the cotton wool alight. The air in the cylinder acts both as a source of heat and an oxidizer for the cotton wool.

Making glue from milk

Running out of glue? You can make it yourself. Ha Ha but I have tried it, is quite time consuming even though it looks easy. So is better to go and buy one. But one thing I need to comment about this glue is that you see it like normal flour with water. But its strength is amazing once you stick it and it dries. I tried to stick metal, glass, wood and all of them stick well. I even tried to pull them apart with strength. But maybe glass and metal have smooth surface so I am able to separate them. However the wood is stick so tightly that I cannot pull the 2 wooden block apart.

So just want to share this receipe, when you REALLY free then you can make the glue yourself. Do not worry about ants or what even though milk powder is used, it is because I think the acid and base have made it so unpleasant that it will not attract ants.

This is how I do it -

1) Dissolve 10g of milk powder in 50ml of warm water

2) Add vinegar or 1M HCl dropwise until the milk separates into curds (white solid) and whey (yellowish liquid)

3) Use a cheese cloth to add as a sieve to separate the curds from the whey.

4) Wash the cheese cloth with the curds inside to remove the acid.

5) These curds is also known as casein and it is then dried on filter paper (as shown).

6) Place the dried casein in a beaker and add 20% sodium hydroxide dropwise and stirred to make it into a homogeneous paste.

7) Finally add 1.5g of calcium hydroxide powder and stirred until a thick creamy liquid is form and this will be the glue.

I tried to leave it for a few days in a covered container and it does not dried up even it is dried just add a drop of water and stir the glue can be used again. Another good thing is that it do not have any glue smell so it is quite safe.

So hope you like my receipe if you are currently unsatisfied with your glue. Try to make one yourself.

Conductor and insulator of electricity

Hi, just happen to teach on conductor of electricity. I do not know why I always have a concept the aluminium is not a conductor of electricity. But when I search the net, a few website say that is a conductor of electric. Anyway just curious and find out why some material cannot conduct electricity but some can?

The reason is thatin conductive materials, the outer electrons in each atom can easily come or go, and are called free electrons. In insulating materials, the outer electrons are not so free to move.
All metals are electrically conductive.

Electric current is the uniform motion of electrons through a conductor.

In other types of materials such as glass where atoms' electrons have very little freedom to move around. While external forces such as physical rubbing can force some of these electrons to leave their respective atoms and transfer to the atoms of another material which form the static electricity which is an unmoving, accumulated charge formed by either an excess or deficiency of electrons in an object.

For electrons to flow continuously (indefinitely) through a conductor, there must be a complete, unbroken path for them to move both into and out of that conductor.

Here will be some of the example of conductor and insulator.

Conductors: silver, copper, gold, aluminum, iron, steel, brass (copper & Zinc), bronze (copper & Tin), mercury, graphite, dirty water, concrete

Insulators: glass, rubber, oil, fiberglass, porcelain, ceramic, quartz, (dry) cotton, (dry) paper, (dry) wood, plastic, air, diamond, pure water.

Protein analysis

Hi all, please visit this website as it really give a good real life animation on how protein can be analyse. http://proteomics.cancer.gov/proteomics_basics/animation.asp