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Spectrophotometry

Spectrophotometry. Spectrophotometry. Terms and definitions………. 1.Electromagnetic radiation. You actually know more about it than you may think! . Electromagnetic radiation.

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Spectrophotometry

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  1. Spectrophotometry

  2. Spectrophotometry • Terms and definitions………

  3. 1.Electromagnetic radiation • You actually know more about it than you may think!

  4. Electromagnetic radiation • The electromagnetic (EM) spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group.

  5. Electromagnetic radiation • Examples of groups or radiation: • visible lightthat comes from a lamp in your house • radio wavesthat come from a radio station are two types of electromagnetic radiation.

  6. Electromagnetic radiation • EM travels through space in the form of a wave • Wavelength • Short ( high energy) nuclear power • Long (low energy) am radio

  7. Electromagnetic radiation • Light occupies a small portion of this spectrum. • Visible spectrum –we see these colors

  8. Think about it… • Each color in a rainbow corresponds to a different wavelength of electromagnetic spectrum

  9. Electromagnetic radiation • Color? • Substances process color because of their ability to absorb and transmit certain wavelengths of visible light.

  10. Electromagnetic radiation • Examples of color: • Chlorophyll, absorbs a high percentage of wavelengths of red and blue light • Green light is not absorbed, it is transmitted from the surface of the leaf to our eyes.

  11. Electromagnetic radiation • The ability of molecules to absorb and transmit light energy is the basis for one of the most widely used procedures for determining the concentration of substances in a solution……………………

  12. Spectrophotometry • is a technique used to measures the amount of light energy that is absorbed or transmitted by a sample • Spectrophotometer

  13. What’s in that tube? • By creating and measuring a series of standards, it is possible to quantify the amount or concentration of a substance in a sample • Serial dilution

  14. Spectrophotometry • 1 – start with a blank

  15. The Blank • In order to effectively use a spectrophotometer we must first zero the machine, we do this using "the blank."

  16. The Blank • The blank contains everything except the substance of interest which absorbs light.

  17. The Blank • Thus, by zeroing the machine using "the blank," any measured absorbance is due to the presence of the substance of interest

  18. Standard Curve • Helps determine the concentration of the unknown • A graph where the Y-axis represents the absorbance and the X-axis represents the concentration

  19. Spectrophotometry

  20. A few more terms…. • 1. Independent variable • The variable that is being manipulated

  21. dependent variable responds to the change made to the independent variable depends on other factors

  22. Example • For example, if you open a faucet (the independent variable) • the quantity of water flowing (dependent variable) changes in response--you observe that the water flow increases.

  23. Hypothesis: • If plants are grown in five different types of soil, then the plant in Soil 2 will grow the tallest. • What is our independent variable?

  24. plants receive the same amount of water • the same amount of sunlight ____________________________ • The only thing that is being changed is the type of soil they grow in, and that is the independent variable

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