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STANDARD UNITS AND MEASUREMENTS


Chemical laboratories have evolved significantly over time. However, some things have not changed since time memorial and most experiments will start with simple measurements of mass, volume, and temperature. These measurements are reported in SI units. There are sevent of them and all other unis are derived from a combination of two or more SI units.

QUANTITY Length Mass Temperature Time Amount of Substance Electric Current Luminous Intensity
NAME Meter Kilogram Degree [Kelvin or Celcius] Second Mole Ampere Candela
SIMBOL m kg K or 0C s mol A cd
EXPERIMENTAL PROCEDURE

This method is a way to find the volume of an irregularly shaped solid if it does not float in the liquid. Since the materials we will use have densities far greater than that of water, (the density of water is 1.00 g/cm3) all samples will sink completely.
First, the mass of the metal sample will be determined by weighing the sample on a toploader balance, here the mass was found to be 5.454 grams.
To find volume, fill a graduated cylinder with enough water to cover the sample, place the sample against the graduated cylinder to see how much water is required. Read the volume and record the value as Vol1, here 4.96 g/cm3. Tilt the cylinder and slide the sample down the side. Read the volume and record the value as Vol2, here 6.98 g/cm3.
Substract [Vol1 - Vol2] and record the value on the fourth column of the datasheet.
Then compute the density:

ρ = Mass / Volume


DATA PROCESSING

The above procedure is to be carried out with a number samples of Metal I Metal II. Suppose you did this for five samples, the average density would be computed as follows:

1 + ρ2 + ρ3 + ρ4 + ρ5]
------------------------
5


The density formula looks like a linear equation with y-intercept equal to zero:
Mass --> Y --> ordinate
Volume --> X --> abscissa
Density --> m --> slope

So you can obtain the density from a graph with Mass in the ordinate and Volume in the abscissa.

Plot the data from Metal I and metal II in each of the sheets of graph paper provided with the handout.
It is advised that you read the graphing guidelines before you come to class.





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