EXPERIMENTS – Ch. 2
Standard System of Units and Measurement
Key Terms:
Metric system, SI system of units and measures, derived units, dimensions, dimensional
analysis, conversion ratios, equalities, arithmetic mean or average, significant figures, rounding,
scientific notation, degree of uncertainty, density, specific gravity, Archimedes principle, hydrometer,
buoyancy, increments, gradations
I Area Determination of Rectangular Index Cards
Chemicals:
Equipment and Materials:
none
ruler with in and cm gradations
index cards (small, medium, large)
Procedure:
1. Measure each side of a rectangular index card (length and width), once in inches and
once in centimeters to the nearest hundredth (0.01), if possible
2. Repeat the measurement two more times and tabulate data.
3. Calculate the mean or average for each set of data.
4. Record results using the following table:
Observations and Results:
Width:
Small index card
in
Medium index card
cm
in
Large index card
cm
in
cm
1
2
3
Mean:
Length:
Small index card
in
1
Medium index card
cm
in
Large index card
cm
in
cm
2
3
Mean:
Questions and Problems:
1. What is the conversion ratio of in and cm? Express the ratio in
2.
3.
4.
5.
6.
𝑐𝑚
𝑖𝑛
𝑖𝑛
and 𝑐𝑚.
Calculate the area of the rectangular index cards in2 an cm2 by using the mean values.
Determine the conversion ratio between in2 and cm2.
Verify your measured results by comparison with literature values.
What is the degree of error?
A photograph is 8x10 in. What is the corresponding size in cm?
II Volume Determination of Regular Shaped Objects by Calculation
Chemicals:
none
Equipment and Materials:
ruler and caliper
plastic cube and metal slug (cylinder)
Procedure:
1. Determine the volume of the plastic cube by measuring the length, width and depth (a x a x a or
a3) using a metric ruler. Tabulate the results in m, cm and mm values.
2. Determine the volume of a metal slug by measuring the diameter of the circular end with a caliper
and the height or length with a metric ruler.
3. Calculate the area of the circular end with the formula A=πr2 (area of a circle) and multiply the
result by the determined length or height of the cylinder to give the volume (V=Ah or V= πr2h)
4. Express the volumes in cm3 or mL.
Observations and Results:
Plastic cube:
Side length (a) = ……….m
……….cm
……….mm
Volume (a3) =
Metal slug:
Area of circular end:
(A=πr2 , r = d/2)
=……….cm2
Volume of cylinder:
(V = Ah) = ………..cm3/mL
……….m3
……….cm3
or mL
……….mm3
Questions and Problems:
1. A liter is defined as 1 dm3. Convert the obtained values for the volume of a cube and
metal slug into liters or dm3.
2. What would be the volume of a glass marble, for which the caliper measured a diameter
of 12.0 mm? (Volume of a sphere = 4/3 πr3)
III Density determination of Regular and Irregular Shaped Objects by the
Volume Displacement Method (Archimedes Principle)
Chemicals:
Equipment and Materials:
Tap water
Sugar cubes or rock sugar
Hexane
graduated cylinders (100mL and 250 mL)
metal slugs, rubber stoppers, corks
Procedure:
1. Mass the solid sample on a digital top-loading balance (scale).
2. Pour a random amount of liquid into the graduated cylinder, submerge the solid object (if less
dense than the liquid push down with a pin or thin piece of wire) and record displaced volume
(Final volume minus initial volume).
Observations and Results:
Tabulate the observed results and add the other information required according to the
following table:
Sample
mass
(g)
dV(mL) D
Liquid
Vf - Vi
(g/mL) used
Metal slug
Irregular solid
Rubber stopper
Cork stopper
Rock sugar or
sugar cube
Questions and Problems
1. Why should the object be insoluble in the liquid used for the liquid displacement method?
2. Why does the displacement method work for any kind of liquid?
3. If the object floats in water, what density is best suitable for a liquid that allows the object to
become completely submerged?
4. Why is the error by pushing down an object that is less dense then the liquid used with a thin wire
negligible when determining the density?
5. A solid object with a mass of 3.55g displaces a volume of 12.0 mL. What is its density?
6. Why is density a material constant?
IV Specific Gravity Determination of Solutions using an Hydrometer
Chemicals:
Sugar solutions of two concentrations:
with red dye (higher conc.)
with yellow dye (lower conc.)
Equipment and Materials:
three large graduated cylinders (250-500mL)
Hydrometers
Procedure:
1. Place the whole amount of the provided sugar solutions each in a tall graduated cylinder. Into the
third one put an equivalent amount of demineralized water.
2. Place hydrometers into the each of the three samples and measure the specific gravity (increasing
values from top to bottom), provided the hydrometers float in the solutions or in the pure water.
Observations and Results:
Solution:
Water (H2O)
Red sugar solution
(sucrose)
Yellow sugar solution
(sucrose)
Specific gravity
Density (g/mL)
Questions and Problems:
1.
2.
3.
4.
How is specific gravity defined?
Why does specific gravity have no units?
Why is the numerical value for specific gravity and density the same for any chemical or object?
What is an alloy? How does the specific gravity or density relate to those of the pure metals
involved?
5. What is the specific gravity of Gold? How much would a cube with a side-length of 1.5cm
weigh?