1. Science, Matter, Energy, and Systems2
Science, Matter, Energy, and Systems
Photo © Borut Trdina/iStockphoto

2. Case Study: Experimenting with a Forest
In New Hampshire, scientists examined changes in water flow/soil nutrient content in a(n):
Control area of an undisturbed mature forest
Experimental area of a nearby deforested site
Results showed lack of vegetation allows more water runoff, loss of nutrients from soil
How might ecologists use basic chemistry and laws of matter to further study ecosystems?

3. 2.1 What Do Scientists Do?
The focus of science is to study how nature works and to use what is learned to predict what may happen in nature.
Scientific methods, or practices, enable scientists to advance knowledge and understanding of how the world works.
Scientific theory: well-tested and widely accepted explanation

4. The Practices of Science
Asking questions
Developing and using models
Planning and carrying out investigations
Analyzing and interpreting data
Using math
Forming explanations
Forming arguments from evidence
Obtaining, evaluating, communicating information

5. Observations, Experiments, and Models Answer Questions About Nature
To answer questions about nature, scientists:
Make careful observations.
Develop hypotheses (possible/testable answers to scientific questions or explanations of what is observed).
Take measurements (collect data, or information).
Experiment and create models (representations of structures/systems).
Use knowledge learned to describe and predict what happens in nature.

6. Values That Support Good Science
Logic
Critical thinking
Objectivity
Open-mindedness
Honest reporting
Collaboration
Peer review: evaluation by others in one’s field (methods, results, reasoning, reliability)

7. Scientific Theories
The goal of scientists is to develop theories and laws based on facts and data that explain how the physical world works.
A scientific theory:
Has been widely tested
Is supported by extensive evidence
Is accepted as being a useful explanation of some phenomenon by most scientists in a particular field or related fields of study

8. Scientific Laws
A scientific law is a well-tested and widely accepted description of observations that have been repeated many times in a variety of conditions.

9. Science Has Limitations
Scientific research cannot prove or disprove anything absolutely.
There are inherent uncertainties in measurements, observations, and models.
Scientists use words such as “overwhelming evidence” to clarify probability or certainty.
Scientists must rely on statistical tools.
As humans, scientists are not free from bias; peer review helps to reduce personal bias.

10. 2.2 What Is Matter?
Matter is anything that has mass and takes up space.
Exists in three physical states: solid, liquid, gas
Two chemical forms: elements (all the same atoms) or compounds (combinations of more than one type of atom)

11. Elements and Compounds
Elements cannot be broken down into simpler forms by chemical means.
Represented by a one- or two-letter symbol (C=carbon, Au=gold)
Arranged in periodic table based on chemical behavior
Currently 118 elements, not all of which occur naturally
Compounds: two or more different elements held together in fixed proportions

12. Atom: Basic Building Block of Matter
An atom is the smallest building block of matter that an element can have that will still retain its chemical properties.
Each atom has three subatomic particles:
Neutrons (no electric charge, inside nucleus)
Protons (positive electric charge, inside nucleus)
Electrons (negative electric charge, move rapidly outside nucleus)
Each atom has a small central nucleus that contains its protons and neutrons.

13. Atomic Number, Atomic Mass, and Isotopes
Atomic number: the number of protons in an atom’s nucleus
Mass number: the total number of neutrons and protons in an atom’s nucleus
Isotopes of an element have the same atomic number, but a different mass number (the same number of protons but a different number of neutrons).

14. Structure of Atoms
Atom: This simplified model depicts a carbon-12 atom. The atom’s nucleus consists of six protons, each with a positive electrical charge, and six neutrons with no electrical charge. Six negatively charged electrons move rapidly outside its nucleus.

15. Molecule: Second Building Block of Matter
A molecule is a combination of two or more atoms of the same or different elements held together by forces known as chemical bonds.

16. Ion: Third Building Block of Matter
An ion is an atom or group of atoms with a net positive or negative charge.
Subscript number: number of positive/negative electrical charges
Important for measuring a substance’s acidity in a water solution (pH)

17. Acidity
The concentration (amount) of hydrogen ions (H+) and hydroxide ions (OH−) in a substance
Measured with a scale known as pH
An acidic solution has a pH below 7 and a basic solution has a pH above 7
A neutral solution has a pH of 7

18. pH Scale
pH Scale: The pH scale describes the acidity of solutions.

19. Molecules of Life
In chemistry, organic compounds are carbon- based compounds that contain at least two carbon atoms combined with atoms of one or more other elements (except CH4).
Hydrocarbons: compounds of carbon and hydrogen atoms
Simple carbohydrates: contain carbon, hydrogen, and oxygen
Polymers (complex carbohydrates): simple organic compounds (monomers) bonded together

20. Polymers Are Essential to Life
What are the major types of polymers?
Proteins: formed by amino acids
Nucleic acids: formed by nucleotides (DNA and RNA)
Lipids (fats, waxes): essential macromolecules not made of monomers

21. Monomers and Polymers
Carbon-based Molecules: Glucose monomers (left) make up complex carbohydrate polymers, such as cellulose (right).

22. Physical and Chemical Changes
Physical changes, such as changes in size or state (ice to water), do not involve changes in chemical composition.
Chemical changes (reactions) involve changes in chemical composition of the substances involved.
Chemists use a chemical equation to show how the chemicals involved are arranged in a chemical reaction.
Chemists use a process of balancing the equation to account for all atoms involved in any reaction.

23. A Chemical Equation: Coal → CO2
Chemical Reaction: Chemical reactions can be modeled with words, symbols, or illustrations.

24. We Cannot Create or Destroy Atoms
Law of conservation of matter
Physical or chemical changes can take place in chemical reactions, but no atoms are created or destroyed in the process.

25. 2.3 What Is Energy? Energy is the capacity to do work.
Kinetic energy (associated with motion):
Examples: flowing water, speeding car, electricity, wind
Thermal energy (heat): total kinetic energy of all the moving atoms, ions, or molecules in a sample of matter, measured as temperature
Electromagnetic radiation: wave energy resulting from changes in electrical/magnetic fields; includes solar energy, which fuels life on Earth
Potential energy (stored energy):
Can be converted to kinetic energy

26. Electromagnetic Radiation
Electromagnetic Spectrum: The electromagnetic spectrum consists of a range of electromagnetic waves, which differ in wavelength and energy content.

27. Energy Quality
High-quality, or concentrated energy, has a high capacity to do useful work.
Examples: high-temperature thermal energy, concentrated sunlight, high-speed wind, energy released from burning fuels)
Low-quality, or dispersed energy, has little capacity to do useful work.

28. Energy Changes Are Governed By Two Scientific Laws
First law of thermodynamics (law of conservation of energy)
Whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed.
Second law of thermodynamics
When energy is changed from one form to another, it always results in less high-quality energy.

29. 2.4 What Are Systems?
A system is a set of components that function/interact in some regular way.
Inputs
Throughputs
Outputs
Form of matter, energy, information
Examples: cell, human body, river, forest, dam, economy

30. System Model
Inputs, Throughputs, Outputs: This greatly simplified model shows the flow of matter, energy, and information into and out of a system.

31. Systems Respond to Change Through Feedback Loops
Feedback is matter, energy, or information that is fed back into a system as input and can affect system behavior.
Feedback loops
Positive feedback loops cause systems to change further in same direction.
Ecological tipping point: natural system locked into positive feedback loop
Negative feedback loops cause systems to change in opposite direction.