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Transcript of Environmental Systems
- A set of interacting components connected in such a way that a change in one part of the system affects one or more other parts of the system
Systems within systems:
Earth is a single interconnected System
To a physiologist, a cod fish is a system
A physiologist who wants to know how a cod fish survives in cold New England waters will consider the codfish as a "system." He will study all internal organs and how they interact.
A marine biologist might study the predator-prey relationship between the cod and herring...yet another system
looks like this guy ate quite a bit of herring...
And then there is the oceanographer
Who wants to know how ocean currents affect fish populations in the North Atlantic (Again, a system)
And we can tie it all together
with a fisheries observer who studies the big picture: fish populations, human activities, laws, ext
But the good thing is, they all have some things in common
They all contain
They all use
Is anything that HAS MASS and OCCUPIES SPACE
Matter is made up of elements
Elements Bond to form Compounds
Electrons are SHARED
Covalently Bonded Hydrogen atoms form a weak "ionic bond" to another atom
Atoms are held together by a charge
Compounds can separate and recombine with other molecules in:
Notice in the equation that no atoms are created or destroyed
Law of Conservation of matter: states that matter cannot be created or destroyed; it can only change form
What does this tell us about hazardous waste?
Measured in Joules (metric)
A 1-watt light bulb for 1 second
Energy v Power
Other Common Units of Energy
Amount of energy it takes to heat a gram of water 1 degree C
Food calorie; always shown with a capital C
1 cal = 4.184 J
1 Calorie = 1,000 calories
British Thermal Unit
Amount of energy expended by using 1 kilowatt of electricity for 1 hour
1 Btu = 1,055 J
Amount of energy expended by using 1 kilowatt of electricity for 1 hour
1 kWh = 3,600,000 J
Energy and power are different
Energy = power * time
Power = energy/time
Here is where stuff gets weird
Think of this like driving....
When you drive, you have a speedometer which tells you how fast you are driving
This can be compared to POWER; the rate at which fuel/electricity is used
If you wanted to know the total DISTANCE you traveled, you would have to multiply your speed by how long you drove for
So say I was driving 60 mph for two hours = 120 miles
This can be compared to ENERGY; the total amount of fuel/electricity used
kW = the RATE at which fuel/electricity is used
kWh = the AMOUNT of fuel/electricity used
ugh, so confusing
...but let's practice
Your electricity bill shows that you use 600 kWh of electricity each month. Your refrigerator, which is 15 years old, could be responsible for up to 25% of this electricity consumption. Newer refrigerators are more efficient, meaning that they use less energy to do the same amount of work. If you wish to conserve electrical energy and save money, should you replace your refrigerator? How can you compare the energy efficiency of your old refrigerator with that of the more efficient new models?
Your refrigerator uses 500 watts when the motor is running. The motor runs for about 30 minutes per hour (or a total of 12 hours per day) The best new refrigerator uses 400 kWh per year
DO THE MATH
1. How much energy does your refrigerator use?
2. How much more efficient is the best new refrigerator compared with your older model?
3. Assume you are paying, on average, $0.10 per kilowatt-hour for electricity. A new refrigerator would cost you $550. You will receive a rebate of $50 from your electric company for purchasing an energy-efficient refrigerator. If you replace your refrigerator, how long will it be before your energy savings compensate you for the cost of the new appliance?
The Three Laws
The first law
Just as matter can neither be created nor destroyed, ENERGY is neither created nor destroyed
The Second Law
When energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes
The Third Law
At zero kelvin the system must be in a state with the minimum possible energy, and this statement of the third law holds true if the perfect crystal has only one minimum energy state. Entropy is related to the number of possible microstates, and with only one microstate available at zero kelvin, the entropy is exactly zero
Aka energy laws
for real this time
it can only change form
meaning converting from POTENTIAL energy to KINETIC energy is not a perfect system- energy is lost as heat in the process
the ease with which an energy source can be used for work
Essentially, some energy conversions waste less energy than others
The second law also states that all systems move toward randomness rather than order
Think of how your room looks just after Mom makes you clean it....and then think of it a few days later
Energy (such as heat) spontaneously disperses from being localized to becoming spread out if it is not hindered from doing so.
Your room will never become clean without an input of energy, but will always become messy
A pot of water would never boil without a heat source; but a boiling pot of water will always cool down
But you totally don't need to know that....
unless you're in AP physics....
Why is it important to study whole systems?
Rather than individual plants, animals, or substances?
Think of studying the battery to figure out how your whole phone works
To see how matter and energy flow in the environment
To be able to predict how changes will effect the entire system
Exchanges of matter or energy occur across system boundaries
Most systems are open
Inputs & Outputs
scientists determine inputs, outputs, and changes in the system under various conditions
People studying systems might perform a
Conducting a system analysis will determine if the system is in a
inputs = outputs
no change is occurring over time
Adjustment to input or output rates caused by changes to a system
Feedback loops allow systems to get back to a steady state
Or can cause things to spiral out of control
Positive Feedback Loops
A positive feedback loop
even more births
Even bigger population
Negative Feedback Loops
A system responds to a change by returning to its original state.
The lake example was a negative feedback loop
A self-regulating system
Think of the thermostat in your home
House gets cold
Heat kicks in
House gets hot
Heat shuts off
500 W / 1000 = .5 kW
.5 kW * 12 h = 6 kWh
Old = 6 kWh * 365 = 2,190 kWh
New= 400 kWh
Difference = 1,790 kWh
Savings per Year = 1,790 kWh * $0.10 = $179
How long? = $500/$179 = 2.79 years
Types of Energy
Energy of Motion
Matter/energy exchanges across system boundaries do not occur