Chemistry 11 Lab #3

Basic (and not so basic) Measurements and Devices II

We will start by finishing the measurements from the last lab AND I will show you how to take those measurements and their reading errors to calculate results with error analysis.

The lab will be set up with a number of work stations.  You can do these in any order you choose.  It is crucial to get reading errors for each measurement.  If you are keen you will do repeated measurements where feasible to get a more accurate error.

Station #1 The Calorimeter

The calorimeter is used to measure the heat energy released in a chemical reaction or the specific heat of a substance (we will be discussing this next in the class).  It does this by measuring the temperature change in the water surrounding a sample.
  1. Use the hot plate to bring a pot of water with a 50 g brass mass in it to the boiling point for 5 minutes.
  2. While the water boils pour 200 mL of tap water into the calorimeter and use a thermometer to measure its temperature (Ti).
  3. Add the 50 g mass to the calorimeter and cover it. 
  4. Wait 5 more minutes and measure the final temperature of the water(Tf).
  5. The specific heat of the brass can be calculated by using the formula:                                                                            .                                                                         specific heat of brass = 16720 J/kgCo *(Tf-Ti)/(92oC-Tf )
    You need not bother doing this calculation unless you are interested. If you do, look up the specific heat for brass to compare.
Station #2 The Spectrometer

The spectrometer is used to infer the substances which make up a sample. Different materials absorb light at different wavelengths in different ways. The apparatus is tocuhy and expensive so I will do this one alongside of you.
  1. Place the known samples in the spectrometer and get a reading for the absorption of light at 650 nm..
  2. Put the unknown sample in the spectrometer and find its reading. Can you see which of the sample sit is more like?
Station #3 The Geiger Counter

Be very careful with the radioactive sources and the lead shielding. Wash your hands after handling them. The geiger counter is used to measure the activity of a radiation source. The measurements units are on the counter dial.

  1. Place each of the sources near the geiger counter probe and note the readings.
  2. Place the lead shielding between the sources and the probe and repeat the readings.
Station #4 The pH Meter

The pH meter is used to measure the acidity of a substance.

  1. Place the meter in the calibrating sample and ensure that it reads 7.0.
  2. Then place the probe in the vinegar (acetic acid) and take a reading.
  3. Rinse the probe and then take a reading of the lye (sodium hydroxide, a base -- the opposite of acid).
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