Transcript Density - nelsonsullivanearthsci

Measurements
Earth Science
International System



From the French Le Systeme
International d’Unites….SI system.
Used by all scientists around the world
to ensure all measurements are
consistent.
Very simple to use! All units are easy
to convert by simply moving the
decimal (uses the power of 10)
International System
Length




Basic Unit: meter
Often measured with a _______ stick
Smaller units: centimeter, millimeter
Centi= one hundredth of a meter
– 1 meter = _____________ cm

Milli= one thousandth of a meter
– 1 meter = _____________ mm
Length




Larger Unit: kilometer
Kilo = 1000 meters
1 kilometer equals 0.62 miles
A 10 km road race = 6.2 miles!
Length


Different lengths require an appropriate
unit
What unit would you use to measure the
following:
–
–
–
–
Distance from home to school_____________
Distance around a track_________________
Length of a pencil______________________
Width of a pencil______________________
Mass





Measure of the AMOUNT OF MATTER in
an object.
Basic unit: Gram
Mass depends on the number and kinds of
atoms – Measured using a balance.
Kg-used for large items, such as a
car/person
G-used for smaller objects
Volume




The amount of space an object takes up
Basic Unit: cm3 or mL (milliliter)
1 cm3 = 1 mL….they take up the same
amount of space.
2 different ways to calculate volume
depending on whether or not the specimen
is a regularly or irregularly shaped object
Volume


Regularly-shaped objects: have smooth
solid side, with a definite geometric shape
Volume=Length x Width x Height (LxWxH)
2cm x 2cm x 2cm = 8cm3
Volume


Irregularly-shaped objects have no defined
shape, such as a rock.
Uses the water displacement method
1.
2.
3.
4.
Record Initial volume
Insert object
Record Final volume
Subtract: V = F – I
9 mL – 2 mL = 7 mL
…..or 7 cm3!
-always measure at the bottom
of the meniscus!
Density





Defined as mass per unit of volume….or
how much mass is in a given space.
How tightly “packed” the atoms are.
The higher the density, the tighter the
molecules are packed together, more mass
in a given space.
Calculated: Density = Mass / Volume
Units: g/cm3 or g/mL
Density




Suppose a substance has a mass of 10 g
and a volume of 10 ml
D = m/v
D = __________ / ____________
D = 1 g/ml…this is pure water, which
always has a density of 1 g/ml
Density



Density is a physical property! It always
stays the same, no matter the size of the
object.
If you break an object in half, each half
will have less mass AND less volume than
the object as a whole
Therefore, the density will still calculate to
be the same.
Density



Example: A rock with a mass of 16 g and
a volume of 8 ml has a density of 2 g/ml
D= m/v D = 16g/8ml = 2 g/ml
If the rock is broken in half, each piece
would have half the mass and volume as
the original
Density
Although the rock is now
smaller, the density
stays the same!
Density is a physical
Property
Can be used to identify
an object
Rock A= 8g & 4 ml Rock B = 8g & 4 ml
Density


Objects of different densities will separate,
with the highest density on the bottom, and
the lowest density on the top.
EX: layers of the earth. The core has the
highest density, its in the center. The crust
has the lowest density, its on the surface.
As you go up from the core, density
decreases with each layer.
Density




Density of water =________________
If an object is greater than 1 g/ml, then it
will sink
If an object is less than 1 g/ml, then it will
float.
Is ice greater or less than 1 g/ml?
Density

1.
2.
3.
Indicate whether the following item would
sink or float in water:
Wood
D=0.67g/ml
_________
Golf Ball
D=4.2g/ml
_________
Ping Pong D=.36g/ml
_________
Density

If you know any two variables (m, v, or d),
you can solve for the other one.
Weight




Measures the force of attraction between
two objects due to gravity
On earth, your weight is a measurement of
the earth’s gravity pulling down on your
mass.
Unit: Newton (pounds in this country)
Measured with a scale
Weight





The force of gravity (weight) depends on mass
and distance
The more massive an object, the more it will
weigh.
The closer two objects are, the more they will
weigh.
You actually weigh less on a mountain than at
sea level! Why?
You’re farther from the center of the earth!
Weight


The moon is much smaller than the earth, &
therefore is made of much less mass
(matter). You would weigh 1/6th of what
you weigh on earth!
Since Jupiter is much larger than Earth, you
would weigh a great deal more! Too
heavy to move even.
Review-fill in the following
formulas
 Mass
=
 Volume
=
 Density
=
Percent Error
Accepted Value – Measured Value X 100
Accepted Value
Review
Terms to know:
 Length
 Mass
 Volume
 Density
 Weight
 Water displacement method