environmental science 13e chapter 2: science, matter, and energy
TRANSCRIPT
ENVIRONMENTAL SCIENCE 13e
CHAPTER 2:Science, Matter, and Energy
2-1 What Do Scientists Do?
• Concept 2-1 Scientists collect data and develop theories, models, and laws about how nature works.
Scientific Method HandoutPlease note this is a bit different than what is in your book
Identify question
Form testable hypothesis
Consult prior Collect data to test hypothesis If hypothesis is
knowledge rejected
Interpret results
Report for peer review
Publish findings
• How is the hypothesis different than the question?
• Why do we do the experiment?
The Scientific Process (3)
• Four features of the scientific process:– Curiosity
– Skepticism
– Peer review
– Reproducibility
Results of Science
– Scientific theories
– Scientific laws
Scientific Limitations
–Always some degree of uncertainty–Observational bias–Complex interactions, many variables
Mathematical models
Core Case Study: A Story about a Forest (1)
• Hubbard Brook Experimental Forest• Question: What is the environmental impact of forest
clear-cutting?• Controlled experiment – isolate variables
• Define – Control group: – Experimental group:Identify each for this experimentWhy do we need a control group?
Core Case Study: A Story about a Forest (2)
• Measure loss of water and nutrients
• Compare results– 30–40% increase in water runoff for which
group?– 6–8 times more nutrient loss for which group?
• Draw conclusions
Fig. 2-1, p. 23
Controlled field experiment. Note V-notched dams built at bottoms of two forested valleys so that all water and nutrients could be collected and measured. Then treesin second valley were cut.
Which is experimental site? Which is control?
Essay Questions on Exam 1
1. List the steps of the scientific method in order and provide a description of each step2. Discuss how the Hubbard Brook Experimental Forest exemplifies the scientific method in terms of first 4 steps
• Quickly write answer to question 1 and 2. Determine what was question, what was hypothesis, and what was done to test the hypothesis in this study (what were the 2 groups, what did they measure, for how long, what did they find out)
2-2 What Is Matter and How Do Physical and Chemical Changes Affect It?
• Concept 2-2A Matter consists of elements and compounds, which are in turn made up of atoms, ions, or molecules.
• Concept 2-2B Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).
What Is Matter?
• Matter – has mass and occupies space
• Element- fundamental substance that has a unique set of properties and cannot be broken down into simpler substances by chemical means ex. gold
• Compound- combinations of two or more elements held together in fixed proportions ex. H2O
– Atoms- smallest unit of matter into which an element can be divided and still have its characteristic chemical properties
– Ions- an atom or group of atoms with one or more net positive or negative charge
– Molecules- combination of 2 or more atoms of the same of different elements held together by forces called chemical bonds
Table 2-1, p. 29
For your reference
Supplement 6, Fig. 6, p. S28
Hydrochloricacid (HCl)
Gastric fluid(1.0–3.0)
Lemon juice,some acid rain
Vinegar, wine,beer, oranges
TomatoesBananas
Black coffeeBreadTypical rainwater
Urine (5.0–7.0)Milk (6.6)
Pure water
Blood (7.3–7.5)Egg white (8.0)
Seawater (7.8–8.3)Baking soda
100
10–1
10–2
10–3
10–4
10–5
10–6
10–7
10–8
10–9
10–10
10–11
10–12
10–13
10–14
01
7
8
9
12
13
14
6
10
11
3
4
5
2
Sodium hydroxide (NaOH)
Phosphate detergentsBleach, Tums
Soapy solutions,Milk of magnesia
Household ammonia(10.5–11.9)
Hair remover
Oven cleaner
pH is based on a log scale
Table 2-2, p. 29
For your reference
Table 2-3, p. 30
For your reference
Organic Compounds
• Carbon-based compounds– Hydrocarbons– Chlorinated hydrocarbons– Simple carbohydrates– Complex carbohydrates– Proteins– Nucleic acids (DNA and RNA)– Lipids
Matter Quality
• Usefulness as a resource – Availability
– Concentration
• High quality
• Low quality
Aluminum ore
Low QualityHigh Quality
Solid
Salt
Coal
Gasoline
Aluminum can
Gas
Solution of salt in water
Coal-fired powerplant emissions
Automobile emissions
Fig. 2-5, p. 32
Changes in Matter
• Physical• Chemical• Law of Conservation of Matter
– Matter only changes from one form to another
– Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed
– See P. 32 Connections
Nuclear Changes (1)
• Radioactive decay – unstable isotopes– Alpha particles
– Beta particles
– Gamma rays
Nuclear Changes (2)
• Nuclear fission (type of rxn in nuclear power plant)
– Large mass isotopes split apart
– Chain reaction
• Nuclear fusion– Two light isotopes forced together
– High temperature to start reaction
– Stars
Fig. 2-6, p. 33
2-3 What Is Energy and How Do Physical and Chemical Changes Affect It?
• Concept 2-3A When energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics).
• Concept 2-3B Whenever energy is converted from one form to another in a physical or chemical change, we end up with lower quality or less usable energy than we started with (second law of thermodynamics).
What Is Energy?
• Energy – the capacity to do work or transfer heat
Types of Energy
• Potential energy – stored energy– Gasoline– Water behind a dam
• Kinetic energy – energy in motion– Wind, flowing water, electricity– Heat – flow from warm to cold– Electromagnetic radiation
• wavelength and relative energy (shorter wavelength, higher energy)
Energy Quality (1)
• High-quality energy – Concentrated, high capacity to do work
– High-temperature heat
– Nuclear fission
– Concentrated sunlight
– High-velocity wind
– Fossil fuels
Energy Quality (2)
• Low-quality energy– Dispersed
– Heat in atmosphere
– Heat in ocean
Laws of Thermodynamics
• First law of thermodynamics – Energy input = Energy output– Energy is neither created or destroyed– Energy only changes from one form to
another
• Second law of thermodynamics – Energy use results in lower-quality energy– Dispersed heat loss
Consequences of the Second Law of Thermodynamics
Why this is relevant to environmental science? • Automobiles
– ~13% moves car– ~87% dissipates as low-quality heat into the
environment• Incandescent light bulb
– ~5% useful light– ~95% heat
Solarenergy
Chemical energy(photo-
synthesis)
Mechanicalenergy
(moving,thinking, living)
Chemicalenergy(food)
Wasteheat
Wasteheat
Wasteheat
Wasteheat
Fig. 2-8, p. 36
Three Big Ideas of This Chapter
• There is no away (Think garbage or chemical disposal: It all goes somewhere. Just because we don’t see it anymore doesn’t mean it’s magically disappeared)
– Law of conservation of matter• You cannot get something for nothing (We can’t get more
energy out than we put in)– First law of thermodynamics (Law of conservation of
energy)• You cannot break even (whenever energy is converted from
one form to another in a physical or chemical change, we always end up with lower quality or less usable energy than we started with)– Second law of thermodynamics