11 Terminology

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11 Terminology

• Element group of atoms with the same number of
  protons.
• Compound chemical substance formed from 2 or
  more elements and which has a definite chemical
  formula. Compounds do not have to formed from
  molecules since compounds can be crystal
  structures such as table salt.
• Mixture substance with components that have not
  combined chemically.
• Chemical Substance - an element, compound, or
  mixture.
• Molecule smallest particle of chemical
  substance that has the same composition and
  chemical properties, e.g. water molecule.

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12 Solids
Crystal Structure Crystal Power? Density
Elasticity Tension and Compression Arches Sc
aling
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Crystal Structure
solids with a regularly repeating pattern are
crystals
Examples Graphite NaCl
hexagonal
cubic
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X-Ray Crystallography
X-Rays are used to determine the structure of
crystalline solids
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Density

• Density mass/volume
• depends on chemical type and structure
• water 1.0 grams/cm3
• ice 0.9 grams/cm3
• copper 8.9 grams/cm3
• lead 11.9 grams/cm3
• gold 19.3 grams/cm3

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Elasticity - ability to regain shape

• elastic material perfectly regains shape
• inelastic material incompletely regains shape
• elastic limit force in which an elastic
  material becomes inelastic

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Hookes Law

• Elastic Force amount of stretch or compression
• F Dx
• Example many springs obey Hookes Law within
  their elastic limit.

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Hookes Law
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Longer objects are easier to stretch. Thicker
objects are harder to stretch.
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Tension, Compression, and Bending
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Strength and Shape
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Scaling

• mass size3
• strength size2
• how does this affect animals and structures when
  changing their size?

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