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Matter
Anything that has mass and occupies space
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States of matter:
- Solid—definite shape and volume
- Liquid—definite volume, changeable shape
- Gas—changeable shape and volume
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Energy
- Capacity to do work or put matter into motion
- Types of energy:
- Kinetic—energy in action
- Potential—stored (inactive) energy
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Forms of Energy
- Chemical energy—stored in bonds of chemical substances
- Electrical energy—results from movement of charged particles
- Mechanical energy—directly involved in moving matter
- Radiant or electromagnetic energy—exhibits wavelike properties (i.e., visible light, ultraviolet light, and X-rays)
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Energy Form Conversions
- Energy may be converted from one form to another
- Conversion is inefficient because some energy is “lost” as heat
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Composition of Matter
- Elements
- Cannot be broken down by ordinary chemical means
- Each has unique properties:
- Physical properties
- Are detectable with our senses, or are measurable
- Chemical properties
- How atoms interact (bond) with one another
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Composition of Matter
- Atoms
- Unique building blocks for each element
- Atomic symbol: one- or two-letter chemical shorthand for each element
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Major Elements of the Human Body
- Oxygen (O)
- Carbon (C)
- Hydrogen (H)
- Nitrogen (N)
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Lesser Elements of the Human Body
- About 3.9% of body mass:
- Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), magnesium (Mg), iodine (I), and iron (Fe)
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Trace Elements of the Human Body
- < 0.01% of body mass:
- Part of enzymes, e.g., chromium (Cr), manganese (Mn), and zinc (Zn)
- Atomic Structure
- Determined by numbers of subatomic particles
- Nucleus consists of neutrons and protons
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Atomic Structure
- Neutrons
- No charge
- Mass = 1 atomic mass unit (amu)
- Protons
- Positive charge
- Mass = 1 amu
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Atomic Structure
- Electrons
- Orbit nucleus
- Equal in number to protons in atom
- Negative charge
- 1/2000 the mass of a proton (0 amu)
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Models of the Atom
- Orbital model: current model used by chemists
- Depicts probable regions of greatest electron density (an electron cloud)
- Useful for predicting chemical behavior of atoms
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Models of the Atom
- Planetary model—oversimplified, outdated model
- Incorrectly depicts fixed circular electron paths
- Useful for illustrations (as in the text)
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Atomic Structure
- Determined by numbers of subatomic particles
- Nucleus consists of neutrons and protons
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