CHAPTER 2

Cards (57)

  • Hubbard Brook Experimental Forest
    • Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site)
  • Stripped site
    • 30–40% more runoff
    • More dissolved nutrients
    • More soil erosion
  • Science
    Discovering how nature works
  • Tools of the scientist
    • Observations
    • Measurements
    • Experimentation
  • Steps in the scientific method
    1. Identify a problem
    2. Gather relevant data
    3. Propose a hypothesis to explain the data
    4. Perform an experiment, collect data, and analyze data to test the hypothesis
    5. Modify the hypothesis as needed
  • Model
    Physical or mathematical representation used to study complex systems like climate
  • Scientific theory
    Well-tested and widely accepted hypothesis
  • Scientific knowledge advances through
    • Scientists publish details of methods and results
    • Peer review provides scientific self-correction
    • New data and analysis can lead to revised hypotheses
  • Critical thinking in science
    • Have a skeptical outlook
    • Evaluate evidence and hypotheses using inputs from a variety of reliable sources
    • Identify and evaluate personal assumptions, biases, and beliefs to distinguish facts and opinions before coming to a conclusion
  • Scientific law or law of nature
    Well-tested, widely accepted description of what happens repeatedly and in the same way in nature
  • Types of science
    • Reliable science
    • Unreliable science
    • Tentative science
  • Limitations of science
    • Scientists cannot prove or disprove anything absolutely
    • Scientists are not free of bias about their own hypotheses and results
    • Systems in the natural world involve a many variables and complex interactions
    • Statistical tools are used to estimate large numbers
  • Matter
    • Has mass and takes up space
    • Exists in three physical states: solid, liquid, or gas
    • Has two chemical forms: elements and compounds
  • Elements
    • Have unique properties
    • Cannot be broken down chemically into other substances
  • Compounds
    Combinations of two or more different elements
  • Atomic number

    Same as number of protons in nucleus
  • Mass number

    Number of protons plus neutrons in nucleus
  • Isotope
    Form of an element with same atomic number but different mass number
  • Atomic theory
    All elements are made of atoms
  • Subatomic particles
    • Nucleus of the atom: Protons have positive charge, Neutrons have negative charge
    • Negatively charged electrons orbit the nucleus
  • Molecule
    Combination of two or more atoms of same or different elements, held together by chemical bonds
  • Ions
    Atom or group of atoms with net positive or negative electric charge, formed when electrons are gained or lost
  • Acidity
    Measure of comparative amounts of hydrogen ions (H+) and hydroxide ions (OH–) in a volume of water solution, measured with pH
  • Chemical formula
    Shows number of each type of atom or ion in a compound
  • Ionic compounds

    Example: sodium chloride (NaCl), tend to dissolve in water and break into ions
  • Covalent compounds

    Example: water (H2O)
  • Organic compounds
    Contain at least two carbon atoms, types include hydrocarbons and simple carbohydrates
  • Organic compounds
    • Contain at least two carbon atoms
    • Exception: methane (CH4)
  • Types of organic compounds
    • Hydrocarbons
    • Simple carbohydrates
  • Macromolecules
    • Complex organic molecules
    • Include complex carbohydrates, proteins, nucleic acids, and lipids
  • Cells
    • Fundamental units of life
    • All organisms have one or more cells
  • Genes
    • Sequences of nucleotides within DNA
    • Instructions called genetic information
    • Create inheritable traits
  • Chromosomes
    Composed of many genes
  • Physical change
    No change in chemical composition
  • Chemical change
    Change in chemical composition
  • We can change elements and compounds from one physical or chemical form to another, but we cannot create or destroy atoms
  • Energy
    The capacity to do work or transfer heat
  • Whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics), and we end up with lower quality or less-usable energy than we started with (second law of thermodynamics)
  • Kinetic energy
    • Energy of movement
    • Heat
    • Electromagnetic radiation
  • Potential energy
    • Stored energy
    • Can be changed into kinetic energy