IB Chem, Treatment of Error and Uncertainty

Note: when finding the line of the best fit to extrapolate your initial temperature (T0), eliminate the initial points where the thermometer was still increasing in heat.

For example, if at 15 seconds, your temperature is 22.8 degrees, at 23.0 degrees at 30 seconds, then begins to level off at 23.2 degrees, do not consider the first two points (this is when the mercury is still slowly moving up to the actual temperature of the solution). Explain this in your lab.

Finding error for extrapolating the initial temperature:

1. For the data set that you just found the line of best fit for, let us say that the first point (that you considered in your line) is (x,y) and the last point is (x1, y1).
2. You will be making two lines, finding the slope and y-intercept of each:
3. Line 1: Using the points (x, y + uncertainty) and (x1, y1 - uncertainty), find the slope and y-intercept.
4. Line 2: Using the points (x, y - uncertainty) and (x1, y1 + uncertainty), find the slope and y-intercept.
5. Find the difference of the two y-intercepts and divide by 2.

Since the thermometers used measured to the nearest degree, the uncertainty of the measured temperatures are +/- 0.5 degrees Celsius.

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IB Chem, Treatment of Error and Uncertainty