Download Density Determinations

Density Determinations Lab
Title: Density determination of liquids and solids
Question: How does type of substance affect its density?
Introduction – Purpose:
-
To determine the density of solids and liquids
To practice and learn good lab techniques
Introduction – Background Research (paraphrase)
For this lab’s background research section in the lab report, you will need to
PARAPHRASE the following in your lab report
The density of a sample of matter represents the mass contained within a unit
volume of space in the sample. For most samples, a unit volume means 1.0mL. The
units of density, therefore, are quoted in terms of grams per milliliter (g/mL) for
most solid and liquid samples of matter.
The density of a sample represents the mass of the specific sample divided by its
particular volume. The equation for density is:
where D = density, M = mass, and V = volume. Because the density does in fact
represent a ratio, the mass of any size sample, divided by the volume of that sample,
gives the mass that 1.0 mL of the same sample would possess. In other words, the
density of a pure substance will always be the same as the density of another sample
of the same substance.
The determination of the density of certain physiological liquids is often an
important screening tool in medical diagnosis. For example, if the density of urine
differs from normal values, this may indicate a problem with the kidneys secreting
substances which should not be lost from the body. The determination of density is
almost always performed during a urinalysis.
Several techniques are used for the determination of density. In general, a density
determination will involve the determination of the mass of the sample with a
balance, but volume measurement will differ from situation to situation. For
irregular solids, it may be possible to determine the volume of the solid from
Archimedes’ principle, which states that an insoluble, nonreactive solid will displace
a volume of liquid equal to its own volume. An irregularly shaped solid is added to a
liquid in a container such as a graduated cylinder and the change in liquid level is
determined. For liquids, a routine method for density determination is to weigh a
particular volume of liquid as contained in a graduated cylinder.
Introduction – Hypothesis (fill in the blanks)
Since ______________________________________________________________________________,
If water, oil, rubbing alcohol, and 40 volume clear developer’s densities are
measured,
Then _______________________________________________________________________________.
Materials
Graduated Cylinder
Scale
Beaker
Distilled water
70% rubbing alcohol
40 volume clear developer
Metal BBs
Baby oil
Methods
Density of BBs
1.
2.
3.
4.
5.
6.
7.
Take mass of beaker
Place BBs in beaker
Take mass of beaker and BBs.
Pour 25 mL of tap water into graduated cylinder
Pour BBs into graduated cylinder with water
Measure new volume in graduated cylinder
Take difference of volumes to get volume of BBs, calculate density
Density of Liquids
1.
2.
3.
4.
5.
6.
Take mass of graduated cylinder
Pour between 15-25 mL of distilled water into graduated cylinder
Take new mass of graduated cylinder, take difference to get mass of liquid
Read volume of liquid from graduated cylinder
Calculate density
Repeat steps 1-5 with rubbing alcohol, 40 volume clear developer, and baby
oil (ONLY USE GLASS GRADUATED CYLINDER FOR BABY OIL)
Data Tables
Table 1. Density of Metal BBs
Unit
(fill
in)
Mass of
BBs and
Beaker
grams
Mass of
Beaker
by itself
Mass of
BBs
Volume
of Water
+ BBs
Volume
of Water
by itself
Volume
of BBs
Density
of BBs
Table 2. Density of Liquids
Liquid
Unit
(fill in)
Mass of
Liquid +
Graduated
Cylinder
Mass of
Mass of
Graduated Liquid
Cylinder by
itself
Volume of
Liquid
Density of
Liquid