1. Science, Matter, Energy, and Systems
Chapter 2

2. 2-1 What Is Science?
Concept 2-1 Scientists collect data and develop theories, models, and laws about how nature works.

3. 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 law
What we find happening over and over again in nature.

4. Scientific Theories and Laws Are the Most Important Results of Science
Peer review
Scientists report their methods, data, and conclusions to others in the same field to examine and criticize.
Paradigm shift
When a large number of experts in a field overthrow an old theory for a new one as a result of new data.

5. 2-2 What Is Matter?
Concept 2-2 Matter consists of elements and compounds, which are in turn made up of atoms, ions, or molecules.

6. Matter Consists of 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.

7. Organic Compounds Are the Chemicals of Life
Organic compounds – compounds contain carbon atoms combined with one another and with various other atoms.
Hydrocarbons: compounds of carbon and hydrogen. Ex. methane (CH4)
Chlorinated hydrocarbons: compounds of carbon, hydrogen, and chlorine. Ex. DDT (C14H9Cl5)
Simple carbohydrates: certain types of compounds of carbon, hydrogen, and oxygen. Ex. glucose (C6H12O6)
All other compounds are inorganic compounds.

8. 2-3 How Can Matter Change?
Concept 2-3 When matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).

9. We Cannot Create or Destroy Matter
Matter can change from one physical form to another or change its chemical composition.
However, 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.

10. 2-4 What is Energy and How Can It Be Changed?
Concept 2-4A When energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics).
Concept 2-4B Whenever energy is changed from one form to another, we end up with lower- quality or less usable energy than we started with (second law of thermodynamics).

11. Energy Changes Are Governed by Two Scientific Laws
The first law of thermodynamics: we cannot create or destroy energy.
We can change energy from one form to another.
Energy input always equals energy output
The second law of thermodynamics: energy quality always decreases.
When energy changes from one form to another, it always degrades from a more useful to a less useful form to a more dispersed form.

12. The Second Law of Thermodynamics in Living Systems
Each time energy changes from one form to another, some of the initial input of high-quality energy is degraded, usually to low-quality heat that is dispersed into the environment.

13. 2-5 What Are Systems and How Do They Respond to Change?
Concept 2-5A Systems have inputs, flows, and outputs of matter and energy, and their behavior can be affected by feedback.
Concept 2-5B Life, human systems, and the earth’s life support systems must conform to the law of conservation of matter and the two laws of thermodynamics.

14. Systems Respond to Change through Feedback Loops
Outputs of matter, energy, or information fed back into a system can cause the system to do more or less of what it was doing.
Positive feedback loop causes a system to change further in the same direction
Ex. – soil erosion, some mechanisms of global warming
Negative (corrective) feedback loop causes a system to change in the opposite direction
Ex. – a furnace turning itself off

15. Positive Feedback Loop

16. Negative Feedback Loop

17. Systems Respond to Change through Feedback Loops
Complex systems show a time delay between the input of a feedback stimulus and the response to it, thus making it difficult to predict the outcome.
Sometimes, feedback can take so long that a system reaches a threshold or a tipping point after which the system fundamentally shifts.
Synergistic interaction – processes and feedbacks in a system can amplify the results.
E.g. smoking exacerbates the effect of asbestos exposure on lung cancer.