H2O Electrolysis

H2O Electrolysis

Splitting Water

Electricity is "created" when certain chemicals react together. We use chemically- made electricity to power many machines from flashlights to a watch or sometimes a car. Yes, there are cars that run on electricity! The devices that store electricity are called batteries. Electricity can also be used to produce chemical changes.

Water is a simple chemical made from two gases -- hydrogen and oxygen. Every molecule of water has two atoms of hydrogen for every atom of oxygen. H2O is the chemical formula for a molecule of water.

If an electrical current is passed through water between electrodes (the positive and minus poles of a battery), the water is split into its two parts: oxygen and hydrogen. This process is called electrolysis and is used in industry in many ways, such as making metals like aluminum. If one of the electrodes is a metal, it will become covered or plated with any metal in the solution. This is how objects are silverplated.

You can use electricity to split hydrogen gas out of the water similar to the process called electrolysis.

Try This

What Do You Need

1. A 9 volt battery
   
2. Two regular number 2 pencils (remove eraser and metal part on the ends)
   
3. Salt
   
4. Thin cardboard
   
5. Electrical wire
   
6. Small glass
   
7. Water

What To Do

1. Sharpen each pencil at both ends
2. Cut the cardboard to fit over glass
3. Push the two pencils into the cardboard, about an inch apart
4. Dissolve about a teaspoon of salt into the warm water and let sit for a while. The salt helps conduct the electricity better in the water
5. Using one piece of the electrical wire, connect one end on the positive side of the battery and the other to the black graphite (the "lead" of the pencil) at the top of the sharpened pencil. Do the same for the negative side connecting it to the second pencil top
6. Place the other two ends of the pencil into the salted water.

1. 
   

Binding Energy Curve

Binding Energy Curve

The mass of a nucleus is less than the sum of it constituent protons and neutrons. If we took the same number of protons and neutrons as in the nucleus we were trying to recreate, we would find the total mass of the individual protons and neutrons is greater than when they are arranged as a nucleus. The difference in mass between the products and sum of the individual nucleons is known as the mass defect. The binding energy is the amount of energy required to break the nucleus into protons and neutrons again; the larger the binding energy, the more difficult that would be.

Binding energy of the elements.
Starting from Hydrogen, as we increase the atomic number, the binding energy increases. So Helium has a greater binding energy per nucleon than Hydrogen while Lithium has a greater binding energy than Helium, and Berilium has a greater binding energy than Lithium, and so on. This trend continues, until we reach iron. It begins to decrease slowly.

The binding energy curve is obtained by dividing the total nuclear binding energy by the number of nucleons. The fact that there is a peak in the binding energy curve in the region of stability near iron means that either the breakup of heavier nuclei (fission) or the combining of lighter nuclei (fusion) will yield nuclei which are more tightly bound (less mass per nucleon).

The binding energy is intimately linked with fusion and fission. The lighter elements up to Fe are available will release energy via the fusion process, while in the opposite direction the heaviest elements down Fe are more susceptable to liberate energy via fission.

Magnitude of Stars

Apparent Magnitude

Early Greek astronomers used a scale of magnitude devised by Hipparchus around the 2nd century BC, which was based on how bright stars appeared with the naked eye. The Hipparchus scale went from magnitude 1, for the brightest stars, up to magnitude 6, for those stars which were barely visible.

When telescopes were invented, it was possible to compare the intensities of the light from stars and it was found that the brightest stars of magnitude 1, were around 100 times the intensity of the faintest stars at magnitude 6. Therefore, each magnitude was, 100 = x5. Then each increase in magnitude was 2.512 times fainter than the last. Telescopes allowed astronomers to observe much fainter stars and now the apparent magnitude scale goes from s to around f,

The apparent brightness of a star is how bright it seems when viewed from the Earth, but a large bright star can appear dim if it is a long way from the Earth and a dim star can appear to be bright if it is close to the Earth, therefore the apparent magnitude has no bearing on the distance from the Earth.

To give an acurate measurement of the brightness of a star we need to make an absolute magnitude scale. The absolute magnitude is how bright a star is when viewed from a distance of 10 parsecs.

In order to find the absolute magnitude we need to know the distance of the star from the sun, how do we do this? The intensity of light decreases with distance from the star. The rate at which it decreases is inversely proportional to the square of the distance. Thus if we have a star of luminosity L if we move a distance d the same quantity of light has to cover a larger spherical area. Therefore, away the intensity I = L/(4πd2).

(1)

The inverse square law for the intensity of light

The apparent magnitude m is given by

(2)

m = - 2.5 log10(I + c)(2)

Where, I is the observed intensity of the object.

From the properties of logarithms, the ratio of the intensities of two stars is.

m1 - m2 = - 2.5 [log2.5(I1) - log10(I2)]

(3)

m1 - m2 = - 2.5 log2.5(I1/I2)(3)

Absolute Magnitude

"The absolute magnitude is the brightness of a star at a distance of 10 parsecs".

M = m - 2.5 log10(I2/102)

(4)

M = m - 5 log(I/10)(4)
Absolute Magnitude and Distance

The relationship between the apparent magnitude and the absolute magnitude is given by

M = m - 5 log10(d/10)

From this equation we can calculate the distance d from the Earth if we know the absolute magnitude. In practise we don't know the absolute magnitude because we cannot travel 10 parsecs from the star in question. We can use several indirect methods to determine its absolute magnitude. If the star is on the main sequence of stars then we can determine the brightness from its parallax.