Chemistry Line Spectra Lab

Quantitative Observations

Wavelengths of Different Colours from Different Light Sources.

Wavelengths of Different Colours from Different gasses.

Wavelengths of Different Colours from Different Chlorides.

Data Processing and Presentation

Wavelengths of Different Colours from Different Lights.

Wavelengths of Different Colours of Different Gases.

Wavelengths of Different Colours from different Chlorides.

Conclusion

Through this experiment, continuous and line spectrums were investigated. The sunlight, and incandescent lighting were viewed as continuous spectrums through the spectrometer, while fluorescent lighting, all the gases in discharge tubes and the chemicals that were burned by the Bunsen burner produced a line spectrum. The line spectrum is a series of line called an element’s emission spectra, which shows the specific wavelengths of the energy that is emitted by excited electrons, while the continuous spectrum is light of all colours produced through absorption spectra. The difference between continuous and line spectrum is that a continuous spectrum shows all frequencies of radiation and a line spectrum only show specific lines of the visible spectrum unique to the substance at fixed wavelengths. In this experiment, line spectrums were produced when electricity was passed through the gas discharge tubes and the gas in the fluorescent light tubes. This is because when light was given off when electricity passed through a gas such as hydrogen, the current excites the atoms of the gas which can jump to an infinite amount of shells and the atoms then emits the absorbed energy in a specific amount of light called a quantum of energy, as electrons fall to a lower energy state. When a narrow beam of this light passed through prism in the spectrometer, a series of individual lines was observed, which converge towards the higher-energy end of the spectrum. Thus Hydrogen, and the other gases that were tested in the gas discharge tube and the fluorescent light tubes produced a line spectrum. The chemicals that were added to the flame of the Bunsen burner works similarly to the gas discharge tubes, except that the flame excites the electrons instead of electricity.  A practical application for passing electricity through a gas could be demonstrated in fluorescent light tubes. The gas contained in a fluorescent tube is mercury vapor. When electricity passes through it, it excites and the mercury atoms which produces a ultraviolet light that strikes a phosphorous coating on the inside of the tube, and the excited phosphorous creates visible light. Because fluorescent lighting has gas in its tubes, it does not produce a continuous spectrum like the other type of lights. In the gases discharge tubes the gases are neutral, but a colour is produced when electricity pass through the gas because electrons were excited and will jump from shell to shell then fall back to its ground state. The electrons emit energy that has a specific frequency; this produced the colour of the gas. This is similar to the colours in a line spectrum. It represents the specific frequency and wavelengths caused by the jumping of electrons from one shell to another. The colours are related to the energy produced when the excited electron return to its ground state.

The sunlight, and incandescent lighting produced a continuous spectrum when viewed through the spectrometer. This is because when the white light was produced from the heated filament in the incandescent light, it was refracted by a prism, which spread out the colours of the visible spectrum, a continuous rainbow of colours formed from the light. However, in the case of the sunlight, the Sun is made up of many different chemicals which all produce their own line spectrum. A continuous spectrum was observed but it is really the many line spectrums of the different elements that make up the sun. Because each different substance have a unique line spectrum; we can identify any substance by matching it with its corresponding spectrum This is used when astronauts are trying to identify chemicals in distant space. They can use a similar instrument like the spectrometer to identify the chemical’s line spectra, with that information; astronauts are able to match it with the corresponding chemicals.

 

Evaluation and Limitations

The random errors of the experiment includes cross contamination of the chemicals while burning it on the Bunsen burner. There could be chemical residue left on the wire or the Bunsen burner. This would give a line spectrum of another substance and alter the results making it inaccurate. Also, a different amount of chloride that was used could have gave different results due to the intensity of the flame which can also be affected by the amount of gas the Bunsen burner had and the amount of time the chloride was burned in the fire. A more intense flame would show brighter lines, which makes it easier to tell the colour and the wavelength of the lines in the spectrum. The loud working environment could also be distracting to the lab member writing down the result because their hearing is impaired while trying to listen to the other member reading what they saw in the spectroscope. Some human errors include the reading of the wavelength and the colour. The wavelength is impossible to be exact with using the spectroscope and the colours were hard to tell especially between indigo and violet, which can alter the precision of the results. Another is the distance and angle the spectrometer was used could give inaccurate results because of the different intensity. There could also be a possibility that the light in the room was observed instead of the light from the gas discharge tubes or the flame of the Bunsen burner. The foggy goggles also impair vision, which lowers the ability to read the spectrometer accurately. Systematic errors include the flaws of the instrument used like the spectrometer which did not work properly since most lens fell through the eye piece. Without a proper spectrometer all the results could be altered.

Improvements include better instruments for precise measuring, a better concentration to the work at hand, cleaner wires for burning the chemicals and better goggles for clearer vision and a quieter environment to focus and communicate with fellow lab members.