CH 4:

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CH 4

• The Chemical Basis of Life

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Concept 4.1

• Life Requires about 25 Chemicals

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1. Four most abundant elements in your body

• Oxygen (65)
• Carbon (18.5)
• Hydrogen (9.5)
• Nitrogen (3.3)
• Trace elements-
• in small amounts/
• BIG importance
• Ex iodine iron

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2. How are elements compounds different?

• Elements
• Distinct properties (solid, green, density)
• All one type of atom
• Will be listed on periodic table
• Ex Na, Cl, O, C
• Compounds
• Properties different from each of elements
• 2 or more types of atoms bonded together
• NOT on periodic table
• Ex NaOH, NaCl

Element Video
Compound Video
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3. Examples of trace elements

• Less than .01
• Ironhelps blood carry Oxygen
• Iodinehelps thyroid function properly
• Usually available through a normal, healthy diet
• Who might have problems?

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4.1 Vocabulary

• Matter
• Element
• Trace element
• Compound

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Concept Check Questions 4.1

• 1. List the four most abundant elements in your
  body, in order of decreasing percent of body
  mass.2. How are elements and compounds
  different?3. Give an example showing the
  importance of trace elements to the human body.

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Concept 4.2

• Chemical properties are based on the structure of
  atoms

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1. Subatomic Particles

• Protons (p)
• Neutrons (N)
• Electrons (e-)
• P N Nucleus (mass)
• e- electron cloud (no mass)

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2. Isotopes Radioactive Isotopes

• Elements with same number of P but different
  number of N
• Same element but with different masses
• Radioactive- decay, can be used as tracers or
  markers

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3. Significance of e- energy levels

• Full levels happy atoms (little reactivity)
• Partially full levels unstable atoms (more
  reactivity)
• Either want to empty levels
• Or fill levels
• By giving, taking or sharing (bonding)

Electrons and Energy Video
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4. Atomic Number

• Identifies the element (type of atom)
• Tells the number of protons in that atom
• Makes it distinct
• Each element has its own properties

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4.2 Vocabulary

• Atom
• Proton
• Electron
• Neutron
• Nucleus
• Atomic number
• Isotope
• Radioactive isotope

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Concept Check 4.2

• 1. Describe three kinds of subatomic particles
  and tell how they are arranged in an atom.2.
  What is an isotope? Explain how radioactive
  isotopes are useful to researchers.3. Describe
  the significance of the number of electrons in an
  atom's highest energy level.4. Explain the
  significance of an element's atomic number.

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Concept 4.3

• Chemical bonds join atoms to one another

Atoms Bonding Video
Intro to Chemical Bonding Video
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1. Ionic Bonds vs. Covalent Bonds

• An electron actually moves from one atom to
  another, will orbit the others nucleus
• Takes a -1 charge with it

Ionic Bonding Video
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1. Ionic Bonds vs. Covalent Bonds

• Electrons are shared between two atoms
• Electron will orbit around both nuclei
• Which ever nuclei it orbits around most, is more
  negative
• Creates a
• polar molecule

Covalent Bonding Video
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2. 3. Molecules

• Moleculesatoms joined together with covalent
  bonds
• Smallest amount of that compound
• Represented with
• Chemical formulas
• Structural formulas
• Models

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4. Number of Bonds (Carbon)

• Usually an atoms can bond 1 time for each empty
  electron space in its orbital

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4.3 Vocabulary

• Ionic bond
• Ion
• Covalent bond
• Molecule
• Chemical reaction
• Reactant
• product

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Concept Check 4.3

• 1. Describe how an ionic bond forms. How is this
  process different from the formation of a
  covalent bond? 2. In a molecule represented by
  the chemical formula C6H12O6, how many atoms of
  each element are present?3. What information
  does a chemical equation provide about a chemical
  reaction?4. A carbon atom has 4 electrons in its
  highest energy level. How many hydrogen atoms
  could become bonded to a single carbon atom?

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Concept 4.4

• Life depends on the unique properties of water

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1. Structure of water molecule

• 2 Hydrogen atoms covalently bonded to 1 oxygen
  atom
• Polar
• A molecule
• Displays hydrogen bonding
• Weak attraction between
• a H atom and another
• slightly negative atom

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2. Attraction between water molecules

• Cohesion sticking of similar molecules to each
  other
• Hydrogens of one water molecule are constantly
  forming hydrogen bonds (and then breaking them)
  with other water molecules
• Cohesion is particularly strong for the compound
  water

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3. Importance of water cohesion

• Keeps large molecules organized
• Particularly important for water when moving up a
  plant
• Also gives water a high
• surface tension

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4. Ice and Water as a solvent

• Thank goodness ice floats due to the way
  hydrogen bonds form
• Cause a low density
• Allows ponds to freeze from top down
• Water is the main solvent in most cells, blood
  and sap
• Can dissolve ionic an some covalent bonds

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5. pH Scale

• Describes how acidic or basic a substance is
• Measures amount of H ions vs. OH- ions in a
  substance
• Buffers Donate absorb H
• Range 0-14
• 7neutral or
• equal amounts

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6. Earth supports life because

• Available liquid water
• Viable temperature from the sun
• Ozone prevents frying up

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7. Water moderated temperature

• Heat entering water breaks bonds
• Once bonds are broken, temperature begins to
  increase
• Prevents rapid and easy increase of temperature
• This is why it takes water so long to boil
• Large bodies of water moderate climate
• Ex The lake effect

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4.4 Vocabulary

• Polar molecule
• Hydrogen bond
• Cohesion
• Adhesion
• Thermal energy
• Temperature
• Solution

• Solvent
• Solute
• Aqueous solution
• Acid
• Base
• pH scale
• buffer

Water Video
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Concept Check 4.4

• 1. Explain how the structure of water molecules
  results in attractions among them.2. Give an
  example of how cohesion among water molecules is
  important to living things.3. Describe the
  information the pH scale provides.4. Name three
  conditions on Earth that make the planet suitable
  for life.5. Explain one way in which water can
  moderate temperature.