Chapter 2Science Review

Bell WorkA hectare (ha) is a land measurement equal to 10,000 square meters. 1 acre=.40 ha

A web search of environmental organizations yielded a range of estimates of the amount of forest clearing that is occurring worldwide:

Estimate 1: 1 acre per second

Estimate 2: 80,000 acres per day

Estimate 32,000 ha per day

How can we convert these figures so that we can compare them?

ObjectivesExplain the fundamentals of Environmental Chemistry and apply them to real world situations

Differentiate between the types of energy and explain energy flow

Explain the fundamentals of Environmental Chemistry and

apply them to real world situations

Understanding Chemistry provides a powerful tool for understanding environmental science and developing solutions to environmental problems

Atoms can form molecules and compounds, and changes at the atomic level can result in alternate forms of elements, such as ions and isotopes

Water facilitates the chemistry of life

Living things depend on organic compounds, which are carbon-based

Reasons to understand Chemistry for APES

Chemistry is crucial for understandingHow gases contribute to global climate change

How pollutants cause acid rain

The effects on health of wildlife and people

Water pollution

Wastewater treatment

Atmospheric ozone depletion

Energy Issues

Etc

pH and Solutions

What is pH?pH stands for “Potential/Power of Hydrogen”

The negative logarithm of the concentration of hydrogen ions in a solution

A high number = a very small concentration of H+ ions in solution

A low number = a very high concentration of H+ ions in solution

Logarithmic scale = each number on the scale represents 10x more or less H+

Elements Important to the Study of Environmental

Science

Ions Important to the Study of

Environmental Science

Brain break

Stand up and turn to the person next to you:

Discuss pH. How many more H ions are found in the next pH level?What is the average pH of rainwater?

Matter is conserved

Law of conservation of matterMatter can be transformed from one type of substance into others, but it can neither be created nor destroyed

Because the amount of matter stays constantIt is recycled in nutrient cycles and ecosystems

We need to consider the results of our actions, especially in terms of pollution

Energy & MatterFixed amounts of each in the universe

Can be converted interchangeably (e = mc2)

Earth is an “open system” regarding energy

Earth is a “closed system” regarding matter

Energy & Mass Laws1: Energy/Matter cannot be created or destroyed

2: Energy is always converted to “lower quality” forms whenever work is done

Atomic Structure

The nucleus is tiny and very dense

The volume is almost entirely the electron cloud

LecturePLUS Timberlake 14

Isotopes

Atoms with the same number of protons, but

different numbers of neutrons.

Atoms of the same element (same atomic

number) with different mass numbers

Isotopes of chlorine

35Cl 37Cl17 17

chlorine - 35 chlorine - 37

Types of IsotopesStable: the nucleus contains enough neutrons to block the repulsive forces of the protons. This keeps the isotope from breaking down over time.

2. Unstable: the nucleus of the atom does not have right amount of neutrons to block the repulsive forces of the protons; this makes the isotope radioactive!

Radioactive IsotopesRadioactive isotopes have unstable nuclei and undergo nuclear decay (breakdown)

2. Nuclear decay involves the emission of energy and/or particles from the nucleus in an attempt to become more stable.

The energy/particles emitted from the nucleus are termed radiation and can be alpha or beta particles and gamma rays.

Isotopes disintegrate at predictable rates

Radioactive elements are unstable. They decay, and change into different elements over time.

Not all elements are radioactive. Those that are listed below are the most useful for geologic dating of fossils are:

U-238 Half-life = 4.5 Billion YearsK-40 Half-life = 1.25 Billion YearsC-14 Half-life = 5, 730 Years

Radioactive Isotopes

17

Radioactive Decay and Half Life

The half-life of an element is the time it takes for half of the

material you started with to decay.

Each element has it’s own half-life

Each element decays into a new element C14 decays into N14 while U238 decays into Pb206 (lead), etc.

The half-life of each element is constant. It’s like a clock keeping perfect time.

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Nuclear Chemistry Review

Three types of radiation

Alpha (He nucleus)

Beta (electrons)

Gamma (EMR wave)

Differences in penetration

Alpha (sheet of paper)

Beta (block of wood)

Gamma (concrete wall)

Fission and Fusion

Fission1 nucleus splits into fragments (chain reaction)

Ex. Nuclear reactor

Fusion2 or more nuclei fuse together

Ex. The Sun

Energy LawsFirst Law

Energy cannot be created or destroyed, only transformed or converted between different forms

Ex. Solar energy to chemical energy during Photosynthesis

During work, energy “in” ALWAYS equals energy “out”

“You cannot get something for nothing”

Second LawDuring work, some energy is degraded into lower quality forms

High Quality (ex. Electricity, Nuclear Fission)

Medium Quality (ex. Normal sunlight)

Low Quality (ex. Geothermal heat)

You always end up with less useable energy than you start with

“You cannot break even”

The Second Law of Thermodynamics in Living

Systems

Brain break

Look at the person at your table across from you. If you are facing the windows, explain the first law of thermodynamics to your partner. If you are facing the board, explain the second law of thermodynamics.

Electromagnetic Spectrum

Environmental “Science”

Some areas of ES research are experimental and lab-based

Most research is field-based, involving the study of highly complex FEEDBACK LOOPS

ES research is characterized byA focus on CONNECTIONS & INTERACTIONS

LONG time periods

SYNERGISTIC connections

Types of PollutionDegradable

Ex. Human sewage, organic matter

PersistentEx. DDT, certain plastics, laminates

Non-degradableEx. heavy metals, lead & mercury

Through-Put Economies

High Through-Put EconomyHigh consumption of both matter and energy

Matter Recycling EconomyReduced matter consumption

Still very high energy consumption

Low Through-Put EconomyReduced matter and energy consumption

Is this possible to achieve?

Inputs, Throughput, and Outputs of an Economic System

Experimental Design

ProblemQuestion to be answered

HypothesisScientifically testable statement

Independent or Manipulated Variable

The one(s) being tested or changed

Dependent or Responding Variable

The one(s) being measured

Control GroupNo M.V. (for comparison)

ConstantsAll other variables influencing the outcome

Precision vs. AccuracyAccuracy

The nearness of a measurement to an agreed standard (ex. how close to 1kg is a 1kg standard weight on a particular balance?)

PrecisionThe degree of reproducibility and consistency of a measuring device throughout multiple measurements

The Effects of Deforestation on the Loss of Water and Soil

Nutrients

Core Case Study: Carrying Out a Controlled Scientific Experiment

F. Herbert Bormann, Gene Likens, et al.: Hubbard Brook Experimental Forest in NH (U.S.)

Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site)

Fig. 2-4, p. 37

Nit

rate

(N

O3

– )

con

cen

trati

on

(millig

ram

s p

er

lite

r)

1972197119701969196819671966196519641963

Undisturbed(control)watershed

Disturbed(experimental)watershed

60

40

20

Year