Experiment #4
MEASUREMENT
We are all familiar with measurements which are expressed as the amount of one
thing for each unit of something else. For example, you may shop for meat sold at a certain
number of dollars per pound ($/lb), or you may compute the mileage of your automobile
in miles per gallon (miles/gallon). In this experiment, you will be asked to measure the
density of a liquid. The density of a substance is usually expressed in grams/mL or g/cm3
(grams/cubic centimeter). This experiment will introduce you to common measuring
devices found in the laboratory including the balance, graduated cylinder and buret, and
require you to exhibit knowledge of mathematical and computer concepts including
graphing, linear equations, slopes and intercepts.
MASS MEASUREMENT
The balance is a laboratory device used to measure the mass of an object. One often
refers to this as “weighing” the object, but actually the mass rather than the weight of the
object is being determined.
The balances in our lab have a precision of ±0.001 g for each measurement. This
precision determines the number of significant figures the measurement will contain.
Every measurement you make on the balance should be recorded to the third decimal place,
i.e. 27 .113 g. The balance has a capacity of 200 grams. Do not try to measure an object
that has a mass higher than 200 grams.
PROCEDURE:
1. Be sure you are wearing safety glasses at all times in the laboratory.
2. Ask your instructor for an explanation of the operation of the balance if you
are uncertain how to use the balance.
3. Mass an object on your person (watch, ring, coin, etc.). List the mass of
that object here:
Be sure that your answer to the simple exercise above includes a unit. For example, if
you listed the number 27.113 for the mass of your ring, one could ask “Your ring has a
mass of 27.113 what? Pounds, ounces, kilograms?” The correct listing should be 27.113
g, which is grams.
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