Scientific Measurements and
Density
Measurements
are an everyday
part of science class.
It is very important to be as
accurate as possible when
taking measurements.
Length
In
science, we use the metric
system. So lengths are
measured in units like
millimeters (mm), centimeters
(cm), meters (m), and
kilometers (km).
Take a look at the meter stick above.
On the bottom, the longest lines represent each
whole centimeter (cm).
The medium length lines are each ½ or .5 of a
centimeter (cm) or 5 millimeters (mm).
The smallest lines are each 1 millimeter.
There are 10 mm in 1 cm and there are 100 cm in 1
meter (m).
Let’s figure out the answers now!
A. 2.3 cm
B. 5.1 cm
C. 10.0 cm
What is the distance between points…
A and B: 2.8 cm
A and C: 7.7 cm
B and C: 4.9 cm
Why is it better to align the meter stick so that the edge of the
object being measured is at the 1 cm mark rather than the end to
the meter stick?
Because the meter stick may be worn at the edge and you
will not get an accurate reading.
But be careful!! If you start at the 1 cm mark, you
must allow for that in your final answer by subtracting
1 cm from your answer.
Length
 In
making a measurement of length, the
meter stick should be placed on its edge
so that the scale rests on the object as
shown on your paper. Can you explain
why?
 Being
eye-level will make your answer
more accurate!
Length
 An
enlarged section of a metric ruler is
shown below. There are letters along
the bottom edge of the ruler. Write the
correct measurement for each letter in
the space next to the correct letter on
your paper.

A. 20.5 cm
 B. 19.3 cm
 C. 21.25 cm
 D. 21.95 cm
 E. 18.3 cm
 F. 20.0 cm
 G. 17.7 cm
 H. 20.95 cm
 I. 22.3 cm
 J. 19.7 cm
Temperature

Temperature is a measure of the average
vibration of the particles that make up a
substance.
 In other words, the faster the particles are
vibrating, the warmer they are and thus the
higher the temperature.
 BE CAREFUL! Temperature and heat are
NOT the same thing!!

Heat is a type of energy, temperature is a
measure of that energy.
Temperature

The instrument used to measure temperature
is a thermometer.
 The units of temperature are degrees. There
are three different degree scales.
 1. Fahrenheit (°F) – used in U.S.
 2. Celsius (°C) - metric
 3. Kelvin (K) – used mostly in science, known
as the SI unit for temperature. The Kelvin
scale is based on absolute zero.
Temperature and your ESRT:
pg. 13
Time
 In
this class, you will be using a
stopwatch most often to measure time.
It’s VERY important to know how to
read one accurately!
 PAY ATTENTION – this is not in your
notes, just watch and learn!
Stopwatches are generally divided into 4 sections: Hours, minutes,
seconds, and milliseconds.
In stopwatch “A” the correct reading would be 4.06 seconds.
In stopwatch “B” the correct reading would be 6.59 seconds.
What would be the readings of stopwatch A and B if you were asked to
round to the nearest tenth? (one place after the decimal)
A: 4.1 seconds
A
B: 6.6 seconds
B
Volume
 Volume
is how much space an
object takes up.
 Both liquids and solids have a
volume.
Volume of Liquids
 The
instrument used to measure
volume of liquids is a graduated
cylinder.
 Most of the time, the units used to
measure volume are milliliters (mL).
Volume of Liquids
meniscus
37.0
8.6
22.0
Volume of Rectangular Solids

The most common instruments for measuring
the volume of rectangular solids are rulers
and/or meter sticks.
 The formula for volume of a rectangular solid
is: V = L x W x H.
 Units are “cubic” units because there are
three sides being multiplied by each other.



cu. cm or cm³
cu. m. or m³
1 cubic centimeter = 1 milliliter
Let’s try it now! – determine
the volume of each illustration
on your paper.
V=LxWxH
V=LxWxH
V=LxWxH
V = (3cm)(3cm)(3cm)
V = (8m)(6m)(3m) V = (4cm)(4cm)(10cm)
V = 27.0 cm³
V = 144.0 m³
V = 160.0 cm³
Volume by displacement: used for
solids that are irregularly shaped.
20.0 mL
25.0 mL
5.0 mL (25 mL – 20 mL)
meniscus
Mass
Mass - how much matter or “stuff” is in an
object.
 Traditionally, the instrument used to measure
mass is a triple beam balance. However, in
these “modern” times, we now use an
electronic balance.
 The 2 units most commonly used to measure
mass are grams (g) and kilograms (kg).

This year you will be using an electronic balance like below.
Basically, turn balance on, press the “zero” button, place object on
the scale and it will automatically give you a reading!
Weight

Weight is the amount of gravitational force
acting on an object.
 Mass and weight are NOT the same thing!!!
Weight is a FORCE, Mass is the “stuff” in an
object.
 The instrument used to measure weight is a
spring scale.
 The metric units of weight are Newtons (N).
The English units of weight are pounds (lb).
Weight
 There
are 2 factors that affect
weight:
 1. The amount of mass the object
possesses.
 2. The amount of gravity acting on
the object.
Weight
Using a spring
scale, the weight of
this ruler can be
measured.
Another object,
which is smaller,
has less mass and
so it weighs less.
Weight
The ruler, here on Earth,
has a certain weight.
However, on the moon, it
weights much less due to
less gravity pushing down
on the ruler.
Density

Density is the amount of matter (stuff) that
occupies a given space.
 In other words, it has to do with BOTH mass
and volume.
 If an object has the same “stuff” in it, but gets
bigger it will be less dense.
 If an object stays the same size, but has more
“stuff” in it, it will be more dense.
Density
Least Dense
Most dense
Above, all three objects are the same size, but the one on the left
has much less “stuff” in it than the one in the middle or the one on
the right, so it is least dense.
The one on the right has the most “stuff” (mass) inside it’s given
volume, so it is most dense.
Density

The formula for density is: D = Mass/Volume
 The formula is found on page 1 of your ESRT.
 Using the density triangle, you can easily
figure out the formulas for mass and volume
as well.
M
D
V
Density
 Instruments:
 For
density of liquids, you would use a
graduated cylinder to get the volume
and then an electronic balance for the
mass.
 For density of solids, you would use a
ruler and V=L x W x H to get the volume
and an electronic balance for the mass.
Density

Units:
 It depends on what the object is and the units
of mass and volume that were used. The two
most common are:
 1. g/mL
 2. g/cm³
 Notice that there are always TWO units in
density because you are multiplying mass
and volume and neither of those cancel each
other out.
Putting it all together now!
Solving Density Problems
Density = M / V
D = 150 g / 10 cm³
V=LxWxH
V = (5cm)(1cm)(2cm)
V = 10 cm³
D = 15 g/cm³
Solving Density Problems
D=M/V
D = 125 g / 50 mL
D = 2.5 g / mL
250
300
Object X
300 mL – 250 mL=
50 mL
What if you already know the density of an
object and asked to solve for mass or volume??
 Use
the density triangle!
 Example: The density of an object
is 5.5 g/mL and the volume is 8 mL.
What is the mass?
44.0 g
Density Relationships
 There
are several factors that may
affect an object’s density.
 We will discuss four:
 Size
 Temperature
 State of Matter
 Pressure
Density vs. Size
SIZE DOES NOT MATTER!!
– as long as the substance
stays the same, the density will NOT
change.
 Ex.) lead has the same density no matter if
it’s a huge piece or a very small piece.
 Relationship
Density
Size
Density vs. Temperature
When an object heats up, the volume will increase, due
to the object getting larger. The mass will stay the
same and thus the density will decrease.
Inverse or
indirect
relationship
density
Temp.
Therefore, the relationship is as temperature increases
density will decrease.
Density vs. State of Matter
solid
liquid
gas
most
least
density
Solid objects have a lot of “stuff” packed tightly together so, they
are most dense. The particles in gases have a lot of room to
move!
•The “water rule” – the ONLY exception to this is that water is
MOST dense in its LIQUID state at 4°C
Water ONLY
Regular
Density
Density
S
L
G
S
L G
Density vs. Pressure
As more pressure is exerted on a gas, the volume will
decrease, due to a smaller area for the particles to move.
Now they are packed tightly together. The mass stays the
same and therefore, the density will increase.
Thus, the relationship is as pressure increases, density
will also increase.
Density
Direct
Relationship
Pressure