Download Unit 1 Density and Connections PowerPoint

Ice
Density: 0.9 g/mL
Water
Density: 1.0 g/mL
UNIT 1: DENSITY
AND
CONNECTIONS
Granite
Density: 2.7 g/mL
Basalt
Density: 3.0 g/mL
After Unit 1 you should be able to:
o Understand how to make observations and develop inferences in
Earth Science
o Calculate density using the proper units
o Work interchangeably within the density equation to determine mass
or volume of a substance
o Understand that density describes how much matter is in a given
volume of a solid, liquid, or gas
o Understand the properties of volume and mass
o Understand how substances in a mixture behave when they have
unique densities
o Understand that heat expands the volume of a substance and
decreases the density, and that cooling a substance decreases the
volume and increases the density
o Navigate the reference tables that use density in some way
o Calculate volume and use the water displacement method
o Convert milliliters to cubic centimeters
o Understand that density of a uniform substance does not change
regardless of size
o Understand how convection currents form
o Understand the special circumstance surrounding water and density
Unit 1 vocabulary you should be able to use and understand:
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Formula
Mass
Volume
Density
Grams
Milliliter
Centimeter
Cubic centimeter
Electronic balance
Water displacement
Ratio
Matter
Contract
Expand
Crust
Tectonic plates
Continental crust
Oceanic crust
Convergent boundary
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Observation
Inference
Triple Beam Balance
Elevation
Jovian planets
Terrestrial planets
Convection currents
The scientific method is driven by a balance between making accurate observations
and developing reasonable inferences from those observations. This course
requires you to think with a scientific mind. Being able to develop sound, evidencebased inferences from observations made in Earth Science will ensure your success.
Making Observations
 Observations are made using the five senses:
 Sight
 Touch
 Taste
 Smell
 Hearing
 Of these five, the sense of sight is the most commonly
relied upon sense in Earth Science investigations.
 Observations often require the use of scientific
instruments to be accurate. A scientific instrument is
any tool that you can use to make measurements or
additional observations.
 Examples: hand lens, electronic balance, triple-beam
balance, graduated cylinder
Making Inferences
 An inference is an educated guess or
conclusion derived from one or more
observations
 For example: A student discovers a
very large boulder in upstate New York
that does not match local bedrock in
the area. An inference could be that
the boulder was transported by
glaciers. The student observed the
differences in bedrock, but did not see
glaciers transport the rock, however
there is supporting evidence for
glaciers covering the area.
Density is a property of matter that is the ratio of mass to volume of a substance.
Understanding how density impacts the behavior of interacting substances is
critical in Earth Science.
The Equation in the Earth Science Reference
Tables
Density = mass/volume
Before we get into the equation as a whole, let’s
consider the components:
 mass and volume
What is mass?
 Mass is the measure of matter
that makes up an object. It is
very similar to weight but is
not the same.
 Object with a high mass: an
anvil, containing iron
 Object with a low mass: a
feather
What is volume?
 Volume is the amount of space an
object takes up.
 Container with a large volume:
water tower
 Container with a low volume: water
bottle
How do you find an object’s mass?
 Place the object on an electronic
balance or triple beam balance
 A triple beam balance requires you to
find the sum of the mass of all three
bars
How can you determine an object’s volume?
 If the object is a regular shape, like a
rectangular prism, the volume can be
determined mathematically by performing
the following calculation (length x width
x height)
 When performing such a calculation,
centimeters are used. When multiplied
(#cm x #cm x #cm), the appropriate units
are cm3.
How can you determine an object’s
volume?
 The second method is water
displacement. Measure the
preexisting amount of water in a
container, then gently place the
sample in the water. Record the
difference between the new
measurement and old
measurement. This value is the
volume of the sample in milliliters
(mL).
 1 mL is equal to 1 cm3, so these units
may be used interchangeably,
although milliliters are commonly
used for liquids or irregular samples.
Before finally diving into density,
let’s consider our earlier examples
for understanding mass.
 Which is heavier, a pound of
iron from the anvil, or a pound
of feathers?
 A pound of which material
would take up the most
volume?
Let’s look back at the equation:
 Density = mass/volume
 Density is simply the ratio of the amount
of mass (matter) inside the space of an
object
 So in our feathers and anvil example, we
can say that the feathers are much less
dense than the iron from the anvil.
Sample Problem:
An Earth Science student is trying to
determine the density of a sample of basalt
she discovered in the field. The sample has a
mass of 60 grams and a volume of 20 mL.
What is the density of the sample?
 Density = mass/volume
Solution: ___________ g/mL
What if an object is cut in half? Does the density
change?
 A student has a wooden block that has a mass
of 36 grams and a volume of 48 cm3. The
density is 0.75 g/cm3
 After cutting the block in half, the mass is now
18 grams, and the volume is 24 cm3. The density
is 0.75 g/cm3
 Density remains the same in the same
material, no matter the sample size.
How can the density of a substance
change?
 Density will decrease if you increase
the volume of an object (expansion).
 Most materials decrease in density by
increasing in volume during heating.
 If the material cools, it will contract
and become more dense.
What do less dense materials tend to
do when mixed with more dense
materials?
 Less dense materials rise!
 More dense materials sink!
 In liquids and gases, this results in
the formation of convection
currents, a transference of
energy upward due to
differences in density.
 Convection commonly takes
place in the atmosphere and in a
layer of the Earth known as the
asthenosphere.
Things to know about density in Earth
Science:
1.
The Earth is layered based on
density, with more dense
materials in the core, pulled there
by gravity
2.
Planets closest to the Sun
(Terrestrial: Mercury, Venus, Earth,
Mars) are more dense than ones
farther away (Jovian: Jupiter,
Saturn, Neptune, Uranus)
3.
When air warms, it will expand and
become less dense, and rise
More things to know about density in Earth
Science:
4. When air cools it will contract and become
more dense, and sink
5. Earth’s crust is made up of plates of
varying densities. More dense plates
(oceanic crust, made of basalt) plunge
below thicker, but less dense plates
(continental crust, made of granite) at
convergent boundaries.
6. The density of liquid water is 1.o g/mL at
about 4 oC, and it decreases as it freezes to
ice.
7. Convective circulation caused by #’s 3 and
4 results in hurricane, monsoon, and land
and sea breeze formation (covered in Unit 12)
Relevant Reference Tables for Density