Chapter 2 - Science, Matter, Energy & Systems


What Do Scientists Do?

  • Scientists collect data and develop theories, models and laws about how nature works


  • What is a hypothesis?
    Answer: A hypothesis is an educated guess about what the answer to a question may be. The process of developing a hypothesis is guided by experience and knowledge and should be a statement of cause and effect that can be tested. A theory is a set of hypotheses.


  • What is the role of hypotheses in science?
    Answer: Hypotheses are essential in science. It is through using hypotheses, theory, research questions and the rigorous process of the scientific method that science can continue to advance.


Hypothesis Example


  • What is a theory?

Answer: is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation




  • What is a model?
    Scientific modeling is a scientific activity, the aim of which is to make a particular part or feature of the world easier to understand, define, quantify, visualize, or simulate. It requires selecting and identifying relevant aspects of a situation in the real world and then using different types of models for different aims, such as conceptual models to better understand, mathematical models to quantify, and graphical models to visualize the subject. Modeling is an essential and inseparable part of scientific activity, and many scientific disciplines have their own ideas about specific types of modeling.


  • What is the relationship between hypotheses and models?
    Hypotheses of specific observations and experiments allow the development of more generalized models to predict what will happen in some other place and time.


  • What is a scientific law?

Answer: is a statement based on repeated experimental observations that describes some aspects of the universe. A scientific law always applies under the same conditions, and implies that there is a causal relationship involving its elements.


Scientific Law vs. Theory: a law describes what nature does under certain conditions, and will predict what will happen as long as those conditions are met. A theory explains how nature works in a more general sense.



  • Big Bang Theory: A general statement of the origin of the universe.
  • Hubble's Law of Cosmic Expansion: provides a concise method for measuring a galaxy's velocity in relation to our own.


The Scientific Method


  • Science is a search for order in nature
  • Scientific theories and laws are the most important results of science
    • Scientific theory
      • Widely tested
      • Supported by extensive evidence
      • Accepted by most scientists in a particular area


Scientific Method Videos:

The Times and Troubles of the Scientific Method

Scientific Method Monty Python

Neil DeGrasse Tyson - Scientific Method




What Is Matter and What Happens When It Undergoes Change?

  • Matter consists of elements and compounds, which are in turn made up of atoms or molecules
  • Whatever matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter)
  • Matter consists of elements and compounds
    • Matter
    • Elements
    • Compounds
  • Atoms and molecules are the building blocks of matter
    • Atomic theory
    • Subatomic particles
      • electrons (elementary particles)
      • protons (composed of three quarks, 2 ups, 1 down))
      • neutrons (composed of three quarks, 1 up, 2 down)


    • Atomic number (O8, Na11, Fe26)
    • Mass number
    • Isotopes
    • Ions
    • pH
    • Molecule
    • Compounds
    • Chemical formula
      • H2SO4
    • Chemical Reaction
      • 2SO2(g) + O2(g) + 2H2O(l) = 2H2SO4




  • Organic compounds are the chemicals of life
    • Hydrocarbons and chlorinated hydrocarbons
    • Simple carbohydrates
    • Macromolecules: complex organic molecules
  • Inorganic compounds
  • Matter comes to life (relationship graphic)
    • Cells
    • DNA: DNA (deoxyribonucleic acid) carries the genetic information in the body’s cells.
    • Genes: A gene is a distinct portion of a cell’s DNA. Genes are coded instructions for making everything the body needs, especially proteins.
    • Chromosomes: Genes are packaged in bundles called chromosomes. Humans have 23 pairs of chromosomes (for a total of 46).
  • Some forms of matter are more useful than others (examples)
    • High-quality matter
    • Low-quality matter
  • Matter undergoes physical, chemical and nuclear changes
    • Physical change
    • Chemical change
    • Nuclear change


What Is Energy and What Happens When It Undergoes Change?

  • The Laws of Thermodynamics Govern Energy Flow
    • Potential energy
    • Sun provides 99% of earth's energy
      • Warms earth to comfortable temperatures
      • Plant photosynthesis
      • Winds
      • Hydropower
      • Biomass
      • Fossil fuels (solar vs. fossil fuels):
        • oil
        • coal
        • natural gas
  • Energy Quality
    • Capacity to do work
    • Concentrated
    • Net Energy Ratio or energy return on investment (EROI): is the ratio of the amount of usable energy acquired from a particular energy resource to the amount of energy expended to obtain that energy resource
      • does not include environmental costs or
      • energy generation intermittency (e.g. no wind).



What Keeps Us and Other Organisms Alive

  • Life is sustained by:
    • The flow of energy from the sun through the biosphere
    • The cycling of nutrients within the biosphere
    • Gravity
  • Ecology is the study of connections in nature
    • Ecology: Study of the Relationship Between Organisms and Their Environment
    • Organism: an individual animal, plant, or single-celled life form.
    • Species (biological classification):
      • Organisms that resemble one another in appearance, behavior, chemistry and genetic makeup
    • population: is a group of individuals of the same species that occupy a given area.

    • community: populations of different species living and interacting together.

    • ecosystem: all the parts of the environment, biotic and abiotic, that interact and function as a unit. Ecosystems are composed of a unique combination of physical conditions (such as topography and soils) and associated sets of plant and animal populations (community). An example of an ecosystem is the Eastern Deciduous Forest of North America.

    • landscape: a combination of ecosystems and communities that are linked together. Can be viewed at different spatial scales. Sometimes difficult to define.

    • biome: broad-scale climatic regions dominated by similar types of ecosystems such as tropical rainforests, grasslands and deserts.

    • biosphere: highest level of ecological systems. The area of the earth that supports all life.


    • The diversity of life graphic
  • The earth's life support system has four major components
    • Atmosphere
      • Troposphere
      • Stratosphere
    • Hydrosphere
    • Geosphere
    • Biosphere
  • Three factors sustain life on earth
  • Sun, Earth, Life & Climate
    • Solar/terrestrial radiation
    • Atmospheric radiation interactions
      • Reflection
      • Scattering
      • Absorption
      • Transmission
    • Greenhouse effect

    Heating Earth's Surface & Atmosphere (W&C Chapter #2)

What Are the Major Components of an Ecosystem?

  • Ecosystems have:
    • nonliving and living components
    • organisms that produce the nutrients they need
    • organisms that get their nutrients by consuming other organisms
    • organisms that recycle nutrients back to producers by decomposition
  • Living & nonliving components
    • Abiotic
    • Biotic
    • Range of tolerance (example)
    • Limiting factor principle


  • Producers and consumers are the living components of ecosystems
    • Producers, autotrophs
      • Photosynthesis:
        • CO2 + H2O + sunlight    -->    glucose + O2
    • Consumers, heterotrophs
      • Primary consumers = herbivores
      • Secondary consumers
      • Tertiary consumers
      • Carnivores, Omnivores
    • Decomposers
      • Consumers that release nutrients
      • Bacteria
      • Fungi
    • Detritivores (examples)
      • Feed on dead bodies of other organisms
      • Earthworms
      • Vultures
    • Aerobic respiration
    • Nutrient cycling and the flow of energy


A generalized model of nutrient cycling





Science Focus: Many of the World's Most Important Species Are Invisible to Us

  • Microorganisms
    • Bacteria
    • Protozoa
    • Fungi
  • Energy flows through ecosystems in food chains and food webs
  • Useable energy decreases with each link in a food chain or web
  • Some ecosystems produce plant matter faster than others do
  • What happens to matter in an ecosystem?
    • Matter, in the form of nutrients, cycles within and among ecosystems and the biosphere, and human activities are altering these chemical cycles
    • Nutrient cycles in the biosphere
  • Rock Cycle (graphic)
  • Ecosystems Video (The Habitable Planet)