Chapter 2

Science, Systems, Matter, and Energy

MODELS AND BEHAVIOR OF SYSTEMS

Usefulness of models Complex systems are predicted by developing a

model of its inputs, throughputs (flows), and outputs of matter, energy and information.

Models are simplifications of “real-life”. Models can be used to predict if-then scenarios.

Feedback Loops: How Systems Respond to Change

Positive feedback loop causes a system to change further in the same direction (e.g. erosion)• the ice-albedo positive feedback loop whereby melting

snow exposes more dark ground which in turn absorbs heat and causes more snow to melt.

Negative (corrective) feedback loop causes a system to change in the opposite direction • predator-prey relationships in ecosystems.

Examples

Positive feedback – change continues in

one direction

Negative feedback – before one population grows exponentiallya feedback to reverse growth occurs

Time Delays

Corrective action of the negative feedback loop takes too long

TYPES AND STRUCTURE OF MATTER

Elements and Compounds Matter exists in chemical forms as elements and

compounds.• Elements (represented on the periodic table) are the

distinctive building blocks of matter.• Compounds: two or more different elements held

together in fixed proportions by chemical bonds.

Atoms

Figure 2-4

Ions

An ion is an atom or group of atoms with one or more net positive or negative electrical charges.

The number of positive or negative charges on an ion is shown as a superscript after the symbol for an atom or group of atoms Hydrogen ions (H+), Hydroxide ions (OH-) Sodium ions (Na+), Chloride ions (Cl-)

The pH (potential of Hydrogen) is the concentration of hydrogen ions in one liter of solution.

Figure 2-5

Compounds and Chemical Formulas

Chemical formulas are shorthand ways to show the atoms and ions in a chemical compound. Combining Hydrogen ions (H+) and Hydroxide

ions (OH-) makes the compound H2O (dihydrogen monooxide, a.k.a. water).

Combining Sodium ions (Na+) and Chloride ions (Cl-) makes the compound NaCl (sodium chloride a.k.a. salt).

Organic Compounds: Carbon Rules

Organic compounds contain carbon atoms combined with one another and with various other atoms such as H+, N+, or Cl-.

Contain at least two carbon atoms combined with each other and with atoms. Methane (CH4) is the only exception. All other compounds are inorganic.

Organic Compounds: Carbon Rules

Hydrocarbons: compounds of carbon and hydrogen atoms (e.g. methane (CH4)).

Chlorinated hydrocarbons: compounds of carbon, hydrogen, and chlorine atoms (e.g. DDT (C14H9Cl5)).

Simple carbohydrates: certain types of compounds of carbon, hydrogen, and oxygen (e.g. glucose (C6H12O6)).

Cells: The Fundamental Units of Life

Cells are the basic structural and functional units of all forms of life. Prokaryotic cells

(bacteria) lack a distinct nucleus.

Eukaryotic cells (plants and animals) have a distinct nucleus.

Figure 2-6

Macromolecules, DNA, Genes and Chromosomes

Large, complex organic molecules (macromolecules) make up the basic molecular units found in living organisms. Complex carbohydrates Proteins Nucleic acids Lipids

Figure 2-7

States of Matter

The atoms, ions, and molecules that make up matter are found in three physical states: solid, liquid, gaseous.

A fourth state, plasma, is a high energy mixture of positively charged ions and negatively charged electrons. The sun and stars consist mostly of plasma. Scientists have made artificial plasma (used in

TV screens, gas discharge lasers, florescent light).

Matter Quality

Matter can be classified as having high or low quality depending on how useful it is to us as a resource. High quality matter is

concentrated and easily extracted.

low quality matter is more widely dispersed and more difficult to extract.

Figure 2-8

CHANGES IN MATTER Matter can change from one physical form to

another or change its chemical composition. When a physical or chemical change occurs, no

atoms are created or destroyed.• Law of conservation of matter.

Physical change maintains original chemical composition.

Chemical change involves a chemical reaction which changes the arrangement of the elements or compounds involved.• Chemical equations are used to represent the

reaction.

Chemical Change

Energy is given off during the reaction as a product.

p. 39

Reactant(s) Product(s)

carbon + oxygen carbon dioxide + energy

C + O2 CO2 energy+

energy+

black solid colorless gas colorless gas

+

Types of Pollutants

Factors that determine the severity of a pollutant’s effects: chemical nature, concentration, and persistence.

Pollutants are classified based on their persistence: Degradable pollutants Biodegradable pollutants Slowly degradable pollutants Nondegradable pollutants

ENERGY

Energy is the ability to do work and transfer heat. Kinetic energy – energy in motion

• heat, electromagnetic radiation Potential energy – stored for possible use

• batteries, glucose molecules

Electromagnetic Spectrum

Many different forms of electromagnetic radiation exist, each having a different wavelength and energy content.

Figure 2-11

Electromagnetic Spectrum

Organisms vary in their ability to sense different parts of the spectrum.

Figure 2-12

Fig. 2-13, p. 44

Low-temperature heat (100°C or less) for space heating

Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing

steam, electricity, and hot water

Very high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors)

Mechanical motion to move vehicles and other things) High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity

Dispersed geothermal energyLow-temperature heat (100°C or lower)

Normal sunlightModerate-velocity windHigh-velocity water flowConcentrated geothermal energyModerate-temperature heat

(100–1,000°C)Wood and crop wastes

High-temperature heat (1,000–2,500°C)Hydrogen gasNatural gasGasolineCoalFood

ElectricityVery high temperature heat (greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity wind

Source of Energy RelativeEnergy Quality

(usefulness)

Energy Tasks

Laws of Thermodynamics

First Law: energy cannot be created or destroyed, but it can be transformed from one form to another

Sunlight chemical energy food(photosynthesis)

Second Law: when energy is transformed, it is degraded to lower quality

Gasoline combustion in car mechanical energy + heat