CHAPTER 2COLLEGE ENVIRONMENTAL SCIENCE

Basics Review

Matter

Matter: all material in the universe that has mass and occupies space It can be solid, liquid, or gas

Law of conservation of matter: matter can be transformed from one type of substance into others But it cannot be destroyed or created

Because the amount of matter stays constant It is recycled in nutrient cycles and ecosystems We cannot simply wish pollution and waste away

Elements

Element: a fundamental type of matter A chemical substance with a given set of properties Examples: nitrogen, phosphorus, oxygen 92 natural and 20 artificially created elements exist

Nutrients: elements needed in large amounts by organisms Examples: carbon, nitrogen, calcium

Atoms

Atoms: the smallest components that maintain an element’s chemical properties

The atom’s nucleus (center) has protons (positively charged particles) and neutrons (lacking electric charge) Atomic number: the number of protons

Electrons: negatively charged particles surrounding the nucleus Balance the protons’ positive charge

The structure of an atom

Isotopes and ionsIsotopes: atoms of an element with

different numbers of neutronsMass number: the number of protons +

neutronsIsotopes of an element behave

slightly differently Ions: atoms that gain

or lose electrons They are electrically

charged

Some isotopes are radioactive and decay

Radioactive isotopes shed subatomic particles and emit high-energy radiation They decay until they become nonradioactive stable

isotopesHalf-life: the amount of time it takes for one-

half of the atoms in a radioisotope to give off radiation and decay Different radioisotopes have different half-lives ranging

from fractions of a second to billions of years Uranium-235, used in commercial nuclear power, has a

half-life of 700 million years

Molecules and compoundsAn attraction for each other’s electrons bonds

atomsMolecules: combinations of two or more

atomsChemical formula: indicates the type and

number of atoms in the molecule (oxygen gas: O2)

Compound: a molecule composed of atoms of two or more different elements Water: two hydrogen atoms bonded to one oxygen atom:

H2O Carbon dioxide: one carbon atom with two oxygen

atoms: CO2

Atoms are held together with bonds

Ionic bonds: ions of different charges bind together Table salt (NaCl): the Na+ ion is bound to the Cl– ion

Covalent bond: atoms without electrical charges “share” electrons Example: hydrogen atoms share electrons – H2

Solutions: electrons, molecules and compounds come together with no chemical bonding Air contains O2, N2, H2O, CO2, methane (CH4), ozone

(O3) Human blood, ocean water, plant sap, metal alloys

Ionic bonds

Animation: Ionic BondsRight-click / Select “Play”

Covalent bonds

Animation: Covalent Bonds

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Hydrogen ions determine acidityWater can split into H+ and OH–

The pH scale quantifies the acidity or basicity of solutions

Acidic solutions: pH < 7 Contain more H+

Basic solutions: pH > 7 Contain more OH–

Neutral solutions: pH: 7

A pH of 6 contains 10 times as many H+ as a pH of 7

Matter is composed of compounds

Living things depend on organic compoundsOrganic compounds: carbon atoms bonded

together They may include other elements: nitrogen, oxygen,

sulfur, and phosphorusCarbon can be linked in elaborate chains,

rings, other structures Forming millions of different organic compounds

Inorganic compounds: lack the carbon–carbon bond

Carbon skeletons

Animation: Carbon Skeletons

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Polysaccharides

Animation: Polysaccharides

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Hydrocarbons

Hydrocarbons: organic compounds that contain only carbon and hydrogen The simplest hydrocarbon is methane (natural gas)

Fossil fuels consist of hydrocarbons Crude oil contains hundreds of types of hydrocarbons

Macromolecules are building blocks of life

Polymers: long chains of repeated organic compounds Play key roles as building blocks of life

Three essential types of polymers: Proteins Nucleic acids Carbohydrates

Lipids are not polymers, but are also essential Fats, oils, phospholipids, waxes, steroids

Macromolecules: large-sized molecules essential to life

Proteins are long chains of amino acids

Proteins comprise most of an organism’s matter

They produce tissues, provide structural support, store energy, transport material

Animals use proteins to generate skin, hair, muscles, and tendons

Some are components of the immune system or hormones (chemical messengers)

They can serve as enzymes: molecules that promote (catalyze) chemical reactions

Nucleic acids direct protein production

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) carry hereditary information of organisms

Nucleic acids: long chains of nucleotides that contain sugar, phosphate,and a nitrogen base

Genes: regions of DNA that code for proteins that perform certain functions

DNA and RNA structure

Animation: DNA and RNA Structure

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DNA double helix

Animation: DNA Double Helix

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Carbohydrates and lipidsCarbohydrates: include simple sugars and

large molecules of simple sugars bonded together

Glucose fuels cells and builds complex carbohydrates

Plants store energy in starch, a complex carbohydrate Animals eat plants to get starch

Organisms build structures from complex carbohydrates Chitin forms shells of insects and crustaceans Cellulose found in cell walls of plants

Lipids do not dissolve in water Fats and oils (energy), waxes (structure), steroids

Cells compartmentalize macromolecules

All living things are composed of cells: the most basic unit of organismal organization

Cells vary in size, shape, and function They are classified according to their structure

Eukaryotes: plants, animals, fungi, protists Contain a membrane-enclosed nucleus Their membrane-enclosed organelles do specific things

Prokaryotes: bacteria and archaea Single-celled, lacking membrane-enclosed nucleus and

organelles

Energy fundamentals

Energy: an intangible phenomenon that can change the position, physical composition, temperature of matter Involved in biological, chemical, physical processes

Potential energy: energy of positionKinetic energy: energy of motionChemical energy: potential energy held in

the bonds between atomsChanging potential into kinetic energy

Releases energy Produces motion, action, or heat

Potential vs. kinetic energy

Potential energy stored in our food becomes kinetic energy when we exercise and releases carbon dioxide, water, and heat as by-products

Insert Figure 2.11

Energy is conserved but changes in qualityFirst law of thermodynamics: energy can

change form but cannot be created or destroyed

Second law of thermodynamics: energy changes from a more-ordered to a less-ordered state Entropy: an increasing state of disorder

Living organisms resist entropy by getting energy from food and photosynthesis Dead organisms get no energy and through

decomposition lose their organized structure

The sun’s energy powers living systems

Energy that powers Earth’s ecological systems comes mainly from the sun

The sun releases radiation from the electromagnetic spectrum Some is visible light

Using solar radiation to produce foodAutotrophs

(producers): organisms that use the sun’s energy to produce their own food Plants, algae, cyanobacteria

Photosynthesis: the process of turning the sun’s light energy into high-quality chemical energy Sunlight converts carbon

dioxide and water into sugars

Moving to lower entropy

6CO2 + 6H2O + sun’s energy C6H12O6 (sugar) + 6O2

Photosynthesis produces food

Chloroplasts: organelles where photosynthesis occurs Contain chlorophyll: a light-absorbing pigment Light reaction: solar energy splits water and creates

high-energy molecules that fuel the … Calvin cycle: links carbon atoms from carbon dioxide

into sugar (glucose)

Light and pigments

Animation: Light And Pigments

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Cellular respiration releases energyIt occurs in all living things (plants, animals, etc.)

Organisms use chemical energy created by photosynthesis Oxygen breaks the high-energy chemical glucose

bonds The energy is used to make other chemical bonds or

tasksHeterotrophs: organisms that gain energy by

feeding on others Animals, fungi, microbes The energy is used for cellular tasks

C6H12O6 (sugar) + 6O2 6CO2 + 6H2O + energy