Chapter 2 Environmental Systems - PowerPoint Presentation

Slide1

Chapter 2Environmental Systems

These lectures contain copyrighted images that are provided in the teacher

materials for

Friedland

/

Relyea

Environmental Science for

AP Textbook. By using these lectures, you guarantee that you have legal access to these images or that you have replaced the copyrighted images with images that you have the rights to use.

You can never do just one thing!

How cats were parachuted onto Borneo

Cats in Borneo example (1950s)

Borneo is an island in Southeast Asia

Borneo has a tropical climate and that leads to the breeding of mosquitos.Mosquitos carry malaria and in the 1950s, there was a malaria outbreakDDT pesticide was sprayed to kill mosquitos and reduce malariaDDT killed the mosquitos and a parasitic wasp, but not the cockroachesThe parasitic wasps controlled the caterpillar population, so the caterpillar population grew, ate though roof beams and roofs fell in.DDT bioaccumulated in the cockroaches, and then in the geckos(who eat cockroaches) making the geckos sick and slowCats caught and ate more of the slow geckos and DDT bioaccumulated in the cats and the cats started to dieWith fewer cats, the rat population increased, which increased the risk of typhus and plague outbreaks which worried localsSo cats were helicoptered onto Borneo and dropped with parachutes to eat the rats to prevent outbreaks of typhus and plague

http://www.skidmore.edu/~mmarx/ScribSem44/Borneo%201.pdf

Warm-up

Read the intro story for

Ch

2 about Mono Lake and notice another example of how “you can never do just one thing”

Make a list of what happened in the chain reaction starting with Los Angeles deciding to divert water from Mono Lake and Owens LakeJust a little historical context about LA water usage:

Systems

Open SystemMost systems are open

Receives input from and produces output to the outside of the system

Closed System

Not common in nature: some underground caves No inputs and outputs

Sort of, but not really closed

Thermodynamics

1

st

Law

Energy cannot be created nor destroyedEnergy can change formsIf energy is “lost” it was really just converted to another type of energy 2nd LawWhen energy is transferred, the amount of energy stays the same, but the quality of the energy is reducedWhen energy changes form, some is converted to a less desirable formEnergy Efficiency = work done/total energy availableHigher efficiency generally means less energy is lost as heat

Which Law?

In a car, only some of the energy from the gasoline is used to propel the car. The rest is lost as heat

.

Nothing can ever be 100% efficient in terms of converting energy to work. When you walk up a hill you gain the same amount of energy you will lose as you walk down. Your computer, TV, and refrigerator all need a fan to keep from overheating. There is no such thing as perpetual motion.

Energy Quality, Efficiency and Loss

Energy quality is how much work can be done with the energy. High quality energy is convenient, concentrated and able to do lots of work. Low quality energy is hard to harvest, transport and/or use.

Energy efficiency is what percent of the energy expended can be used to do work.

Incandescent light bulbs are only 5% efficient. The other 95% of the energy is lost as heat

LEDs can be 85% efficient, meaning on 15% of the energy is lost as heat

Feedback Loops

Positive loops

are runaway cycles where a change in a certain direction causes further change in the same direction

Population growth : more people are born, more people then reach reproductive age and have children, which leads to more people.

Negative loops occur when a change in a certain direction leads to a lessening of that changeThermostat

What kind of feedback?

The

baby boom resulted in lots of children which meant the US population grew. Those children grew up and had more babies making the population continue to grow -

Cole

takes a nap and gets a sticker when he gets up (yay stickers!) so the next day he takes a nap so that he will get another sticker - Cole does not take a nap and has to go to bed 1 hour earlier meaning he misses out on taking a walk, so the next day he takes a nap so he can stay up for the walk – Cole throws a temper tantrum, which means that Mommy stops doing whatever she is doing and he gets to sit in Mommy’s lap and “talk” about what he did wrong and then Daddy “talks” to him about it later that night, so he keeps throwing temper tantrums so he can have Mommy and Daddy’s undivided attention - Air conditioner and thermostat – Compounding interest –

Half life math

Radium has a half-life of 1500 years. How long will it take for 250kg of Radium to decay down to less than 10kg

?

The

half-life of Pa-234 is 6.75 hr. How much of a sample of this isotope remains after 20.25 hr?

pH math

pH = -log [H+

]

If the pH is 5, what is the

[H+]?If the [H+] is 1 x 10-7M, what is the pH?How much more basic is something with a pH of 11 than something with a pH of 9?

Energy Efficiency Math

The second law of thermodynamics states that when energy is converted from one form to another, some of the energy is converted to a less useful form of energy (i.e. heat). Compare the overall efficiency of an incandescent light bulb (5% efficient) and an LED light bulb (85% efficient) from power plant to light generation.

The conversion of coal to electricity is 35% efficient and the transfer of the electricity from the power plant to your home is 90% efficient.

Math Warm-up

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 percent 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).How much energy in kWh does your refrigerator use per year? (multiply energy use in watts (W) by hours/day to get Wh/day, then convert to kWh/yr)

How much more efficient is the best new refrigerator compared with your older model? The best new model uses 400 kWh per year.

Assume

that you are paying, on average, $0.10 per kilowatt-hour for electricity. A new refrigerator would cost you

$500 with an energy saving rebate. If

you replace your refrigerator, how long will it be before your energy savings compensate you for the cost of the new

appliance?

Math Practice

What is the pH of a pond with an [H

+

] of 1 x 10

-4.5 M?What is the [H+] of a pond with a pH of 6.3?If you started with 200 g of Carbon-14 and Carbon-14 has a half-life of 5,730 years, how old is an item that has 12.5 g of Carbon-14 remaining?