BBC: Chapter Two

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BBC Chapter Two

• Simple Things of Life (Chemistry)

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Some Basics

• Living things composed of chemicals
• Another term is matter
• Matter anything that has mass and occupies space
• Mass how much of something
• Weight gravitys affect on mass

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Energy

• Kinetic energy the energy of motion, Doing
  something
• Potential energy energy that can become kinetic
  energy, stored energy

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Temperature

• Temperature is a measurement of the energy of
  motion the higher the temperature, the faster
  things (molecules) are moving

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Matter the States

• Solid molecules packed tightly together. Solids
  have fixed shapes and possess low energy.
• Liquid more loosely packed, but still possess a
  strong attraction for each other. Maintain fixed
  volume under normal circumstances, medium energy.
• Gas very loose attraction and organization.
  Highest energy.

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Elements

• All matter composed of one or more element(s)
• Elements are the smallest units that possess
  unique characteristics
• 12 most important C, H, O, P, I, N, S, Ca, Fe,
  Mg, Na, K
• The periodic table

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Atoms and compounds

• Single units of an element are called atoms
• Two or more atoms form molecules
• Another term compound. Two or more elements
  combining together in fixed ratios
• Mixtures two or more compounds combining
  together (not always in the same proportions)

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Atomic structure

• Three particle types.
• Nucleus the center. Also contains most of the
  mass.
• Protons particles that contain a positive charge
• Neutrons particles that contain no charge
• Electrons (outside the nucleus) contain a
  negative charge

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The Atom
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• Heavier/bigger atoms contain more particles
• Each elemental atom contains a number of protons
  called atomic number.
• Typically, the number of protons number of
  electrons
• Unlike protons, the number of neutrons the atoms
  of an element possess can vary, but most of the
  atoms will have a similar number

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Atomic mass

• Atomic mass is the number of protons and neutrons
• How can we determine the number of neutrons an
  atom possesses?
• Atoms with differing numbers of neutrons are
  called isotopes
• Some isotopes are radioactive

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Chemical reactions

• Interactions between atoms/molecules are called
  reactions.
• Chemical reactions involve energy and a
  recombination of molecules
• reactants ? products
• Na Cl ? NaCl
• Most reactions more complicated than this

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Some more examples

• HCl NaOH ? NaCl H2O
• C6H12O6 O6 ? 6 CO2 6 H2O NRG

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Atomic models

• Electrons move in specific areas relative to the
  nucleus
• Why?
• Electrons are attracted to positive charge of
  protons
• Electrons tend to move away from the nucleus due
  to the energy of their movement
• Electrons are repelled from one another

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• Electrons are found in regions called levels
• The lower the level number, the closer that level
  is to the nucleus
• The Bohr model stated that electrons circle the
  nucleus

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• We now know that the Bohr model is incorrect
• Different levels have different shapes.
• These shapes are three dimensional
• All the electrons in a level contain the same
  amount of (kinetic) energy
• For example, the first two levels are roughly
  sphere shaped

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• Fig. 2.4

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Electron clouds

• Electrons dont orbit in their levels
• The nature of electrons
• Clouds the shape of a level
• orbitals and shells level

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• As an atom (element) gets larger (heavier), the
  number of electrons it possesses gets more
  numerous
• The first level of any atom can hold two
  electrons
• The second and subsequent levels can hold up to
  eight electrons (sometimes more) (Table 2.2)

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Atom happiness

• For an atom to be happy (more stable), it will
  try and have complete (full) outer levels (octet
  rule)
• Outer shells called valence
• Valence electrons are what participate in
  chemical reactions

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Ions

• Some atoms, can contain unequal numbers of
  protons and electrons
• If an atom has more protons than electrons
• And vice-versa
• Many elements found by themselves in nature are
  only found as ions Na, K, Ca, Cl, P

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Ions

• Atoms that possess a positive charge are called
  cations Na
• Atoms that carry a negative charge are called
  anions Cl-
• Some atoms would be more stable if they lost or
  gained electrons, and that is why ions are found

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Bonding

• Chemical formula states what atoms (or ions) are
  in a molecule
• Empirical formula also gives the proportions of
  each atom H2O
• Structural formula reveals the spatial
  relationships

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Bonding

• As far as bonding goes, only the electrons in the
  outermost shell (level, orbital) count
• Valence electrons
• Atoms are happiest (most stable) when their outer
  shells are full (in most cases, this means 8
  electrons)
• e.g. hydrogen (H)
• e.g. sodium (Na)

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Bonds, chemical, Bonds 001

• Some atoms either lose or gain electron(s)
• When atoms lose an electron, they develop a
  positive charge
• When atoms gain an electron, they develop a
  negative charge

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Ionic bonds

• Atoms with charge are called ions
• Ions with opposite charges attract one another
  and thus are bonded
• These types of bonds, resulting from charges, are
  called ionic bonds
• Salts found in the human body, such as NaCl, are
  formed by ionic bonds

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Disassociation

• Because its nature, ionic bonds come apart in
  water

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Bonds, chemical Bonds 002

• Many atoms, like carbon (C), dont give up or
  steal electrons from other atoms
• Still, like most other atoms, C is most stable
  with a full outer shell
• Atoms such as this share electrons with other
  atoms covalent bonding

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• Covalent bonds are very common in living
  organisms
• C, N, O, form covalent bonds, as does H
• e.g. H2O
• Additionally, atoms can share more than one pair
  of electrons O N
• Carbon is special

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Bonds, chemical Bonds 003

• Sometimes, due to its shape, parts of a molecule
  will possess (partial) charges.
• However, the overall charge of the molecule is
  still neutral
• e.g. water

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Polar bonds

• The negative ends of the molecule are attracted
  to the positive ends of other molecules, and
  vice-versa
• When the positive end is hydrogen, these
  attractions are called hydrogen bonding

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• Hydrogen bonding gives water some special
  properties
• High surface tension and cohesion
• High specific heat
• Universal solvent
• Unique densities
• H-bonding is also important in DNA and proteins

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Acids, bases, and pH

• Acids give off H ions when placed in water
• Strong acids completely disassociate in water
• Weak acids only partially come apart

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• Bases give off OH- or take up H ions
• There are strong and weak bases, as well

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• When acids and bases meet, they neutralize each
  other to form salts
• HCl NaOH ? NaCl H2O

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pH

• The pH scale measures how acidic or basic
  (alkaline) a solution is
• The lower the number, the more acidic
• The higher the number, the more basic
• Neutral 7

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The pH scale