Science 10 Unit D: Energy Flow in Global Systems I
Energy Getting to the Biosphere
We look at 4 big
ideas in this unit:
1. How energy moves from the Sun to the Earth
and through the Biosphere.
2. How energy moves around the Earth.
3. How different amounts of energy make for
different biomes on Earth.
4. What happens when energy flow goes wrong.
All of the energy we use on Earth has in one way or
another come from the sun. But how exactly does
that energy get here?
- the sun transfers its energy through light
- light is called electromagnetic radiation, or EMR,
as it is made up of alternating electric and magnetic
waves.
- EMR can be broken down into different categories
based on the wavelength of the wave.
- the narrow zone around the Earth
where life exists.
The biosphere is made up of three parts:
- atmosphere (air)
- hydrosphere (water)
- lithosphere (ground)
1. The Atmosphere
- roughly 500 km altitude above Earth’s surface
- made up of gases and bits of dust.
- mostly N2(g), some O2(g), very small amounts of other
gases.
The atmosphere is broken into four layers:
4) Thermosphere (~300 km up)
3) Mesosphere (~80 km up)
2) Stratosphere (~50 km up)
1) Troposphere (~10 km up)
As one moves upwards, atmospheric pressure and
temperature decrease.
Note that the gases that make up the ozone layer are found
mostly in the stratosphere.
Altitudes and Temperatures
- Generally, as the altitude increases, the temperature of the
air decreases.
- In areas near mountains, cool air can be trapped close to
the ground by a layer of warmer air.
- This process is known as a temperature inversion.
2. The Lithosphere
- the livable part of the Earth’s crust, including that under
the ocean.
Some of these types of waves are absorbed by the
Earth. The really high energy waves (UV, X-Ray,
gamma, cosmic) are mostly shielded by the Earth’s
ozone layer, except in areas where the ozone layer
has been depleted.
The amount of the Sun’s radiation absorbed by
the earth is called the Earth’s insolation.
After the energy is absorbed, it moves through the
Earth’s biosphere.
3. The Hydrosphere
- the livable part of the Earth’s water
- about 97% is salt water, only 3% is fresh water (of that,
even less is in liquid form that we can drink).
Practice: page 348 #11 and 13
Absorption and Reflection by the
Biosphere
Not all of the Sun’s energy is simply taken by the Earth.
Some energy is absorbed and some is reflected. this
happens in all 3 layers of the biosphere.
- Absorbed energy (insolation): re-emitted as heat,
drives water cycle, used for photosynthesis.
- Reflected energy: goes back to space, or is reabsorbed.
Absorption in the Atmosphere
- Each layer contains different gases, all reflect and
absorb different energies.
- O2(g) and N2(g): absorb high energy radiation (X-rays,
gamma rays)
- Ozone: absorbs UV radiation.
- CO2(g) and H2O(g) absorb IR radiation (heat).
- Visible light and radio waves are not absorbed.
Insolation and the Angle of Inclination
The northern hemisphere is at it’s maximum angle
towards the Sun on approx. June 21st every year. This
day is called the summer solstice and is the longest day
of the year (most hours of sunlight).
The northern hemisphere is at it’s minimum angle
towards the Sun on approx. Dec 21st every year. This
day is called the winter solstice, the shortest day of the
year (fewest hours of sunlight).
There are also two days throughout the year where the
number of hours of sunlight are equal to the number of
hours of darkness. These are called equinoxes and
occur on the 22nd of Sept. and March.
Places higher up in latitude (farthest north) and lower
down in latitude (farthest south) are farthest from the
sun in winter and closest in summer. Therefore, they
have the longer longest days and shorter shortest days.
Places near the equator receive days of mostly equal
length throughout the year.
Insolation and the Angle of Incidence
Insolation is also affected by the angle the Earth makes
with the Sun’s rays. This angle is called the angle of
inclination.
The current angle of inclination is about 22.5 degrees.
When our part of the Earth is tilted
away from the Sun, we experience
winter.
When our part of the Earth is
tilted towards the Sun, we
experience summer.
The distance from the Earth to the Sun DOES NOT have
an effect on seasons for two reasons:
1) While the Earth-Sun distance DOES change
throughout the year, it isn’t by very much.
2) If the Earth-Sun distance DID change the seasons,
then everywhere on Earth would have winter when we
were farthest from the Sun and summer when we were
the closest; this just doesn’t happen.
As the angle of incidence increases, the amount of
sunlight is spread out over longer distances. This
means the light has less energy per m2 of Earth: it is
diluted.
The angle of
incidence
increases as we
go further away
from the equator. The Sun’s rays have less intensity,
resulting in an overall cooler climate.
Both angle of incidence and angle of inclination have
an effect on climate. Now we see why places on the
Earth closer to the equator have less extreme climates;
they have smaller angles of incidence and are not as
affected by the Earth’s tilt or angle of inclination.
Specific Heat Capacity
Practice: page 369 #14
City A is located on the equator and city B is at the
North Pole. In a table, compare the relative number of
hours of daylight and the amount of insolation that
would be received in these cities on Dec. 21st and
Mar. 21st of any year.
Equator
(A)
North Pole
(B)
hours of
daylight
insolation
Albedo
The percent amount of reflection the lithosphere does
is called albedo. The average albedo for the Earth is
30%.
The Net Radiation Budget
Energy Moving In the Biosphere
- the difference between the amount of incoming radiation
and outgoing radiation from the surface.
Temperature vs. Heat – the average of the kinetic energy
of all the particles in an object is called temperature. The
total of the kinetic energy of all the particles is called heat.
Incoming radiation = all energy that reaches the surface.
Outgoing radiation = radiation emitted that is not
reabsorbed by the atmosphere.
This leads to the First Law of Thermodynamics:
This could also be written as:
Three ways this thermal energy transfer takes place:
The greenhouse effect, albedo and amount of absorption
and reflection all contribute to the Earth’s net radiation
budget.
If the balance changes, the Earth will:
- heat up (incoming > outgoing) or
- cool down (outgoing > incoming)
- Conduction: transfer through the bumping together and
contact of particles.
- Convection: particles moving in the form of currents in
liquids and gases transferring energy.
- Radiation: energy transfer through vibrating electrons
through sunlight, infrared, etc.
Climate in the Biosphere
Energy Transfer in the Atmosphere
Climate is the trend in temperature, atmospheric pressure,
humidity and precipitation of a region over a long period
of time (min 30 years). The term weather applies to those
conditions as they are at one place and time.
- absorption of energy through radiation from the Sun.
- movement of energy through convection and wind.
Climate results from the interactions among the
components of the biosphere.
Practice: page 369 #3, 4, 6, 10, 11, 13
As much of the EMR is reflected from Earth, it is
necessary that some be redirected back to keep the
Earth warm. This re-reflecting is the job of the
Greenhouse Effect.
In general, global wind patterns stay the same over time.
Winds that blow east along the equator are called trade
winds, winds that blow east are called easterlies and west
are called westerlies.
The wind does not blow in straight lines because the Earth
is not actually a flat surface. Winds tend to move energy
in circles: this is called the coriolis effect.
- Winds in the Northern Hemisphere go clockwise
- Winds in the Southern Hemisphere go counter-clockwise
The specific heat capacity (c) of a substance is the amount
of energy required to raise the temperature of 1 g of that
substance by 1°C.
The specific heat capacity of water is 4.19 J/g°C. This is
actually quite large, aluminum for example is only 0.897
J/g°C. This means it takes a lot of energy to raise the
temperature of water by even one degree. Water therefore
holds onto that energy much better than most materials,
meaning that areas surrounded by water stay warmer
longer as the heat is slowly released in cold weather. They
also do not get as hot as the water can absorb much of the
heat present in the atmosphere.
Calculating
Thermal
Energy
ex) Calculate the amount of energy 250 g of water will
release as it cools from 80.0°C to 20.0°C.
ex) Determine the final temperature of 500 g of water if
you were to add 9.00 kJ to it. Assume its initial temp is
20.0 °C.
ex) If you add 3.57 kJ of energy to a substance, its
temperature increases from 20.0°C to 30.0°C. If the mass
of the object is 1.51 kg, determine the specific heat
capacity of the object.
Energy Transfer in the Hydrosphere
The Earth has a natural greenhouse effect: gases like
CO2, CH4 and N2O all trap reflected sunlight and
allow for greater absorption. Without this naturally
occurring effect, the Earth would be on average 30°C
colder.
Thermal energy is transferred vertically through oceans
via convection currents. Warm water tends to rise, and
cooler water sink.
After going through these notes, complete these
textbook questions:
Page 408-409 #1-10, 23-27, 29-32, 36, 38
Climatographs showing average temperature and
precipitation over the span of a year for cities near the
ocean in Canada vs. cities that are land locked show that
show average temperature increases as you move closer to
the ocean. Why is this? It has to do with the specific heat
capacity of water.
ex) A student is trying to identify an unknown liquid. The
liquid absorbs 250 kJ of energy and experiences a change
in temp. of 7.2°C. The mass of the sample is 14.11 kg.
What is the unknown liquid?