Biology Chapter 2: The Atoms and Molecules of Ancient Earth
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- Chemical Evolution
- Simple chemical compounds in the atmosphere & oceans combined to form larger and more complex molecules, which led to the origin of life
- What two major events happened as the Earth began to cool?
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1. Water rained out of the atmosphere to form the first ocean
2. Many volcanoes existed, which spewed volcanic gas into the atmosphere - What is the important characteristic of the outer-most shell of the valence electrons?
- The number of unpaired electrons (or valence) is very important for chemical bonding patterns.
- Describe covalent bonding patterns
- Valence electrons are shared between 2 atoms, which bind together to form molecules; equal sharing forms non-polar molecules/ unequal = polar.
- Electronegativity
- The degree with which atom's share their valence electrons in covalent bonds.
- Describe ionic bonds
- Valence electrons are completely transferred from one atoms to another; ions form, bonding them together.
- What is the difference between cations and anions?
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Cations- Positively charged ions
Anions- Negatively charged ions - In a molecule, what dicates the behavior and function?
- The overall shape (bond angles).
- Molecular Formula
- The number and type of atoms in a molecule.
- Structural Formula
- Which atoms are bonded together; single, double, and triple bonds are shown by single, double, and triple dashes.
- Molecular Weight
- The sum of the mass numbers of all the atoms in a molecule.
- Molarity
- The number of moles of a substance per Liter.
- Chemical Reaction
- An event in which one substance is combined with others or broken down into another substance.
- T/F Changing the concentration of the reactants or of the products can disturb the chemical equilibrium.
- True.
- Eplain the difference between endo and exothermic reactions.
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Endothermic- Heat is absorbed in the chemical process; driven to right
Exothermic- Heat is released; equilibrium driven to left. - Energy
- The capacity to do work or supply heat; exists either as stored potential energy or active motion.
- Thermal Energy
- The kinetic energy of molecular motion.
- Temperature
- The measure of how much thermal energy its molecules pocess.
- Heat
- The transferrence of thermal energy from one molecule to another.
- What happens when an electron 'falls' into a lower electron shell?
- It experiences a loss of potential energy because it uses some it its kinetic energy in the fall.
- First Law of Thermodynamics
- Energy is converted from one form to another; it can neither be created or destroyed.
- Second Law of Thermodynamics
- Entropy always increases in a closed system.
- Chemical Energy
- The potential energy stored in chemical bonds.
- What makes reactions spontaneous?
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1. Products have lower potential energy than reactants (exothermic) (H)
2. Products are less ordered than reactants (increased entropy) (S) - Gibbs Free-energy change
- Delt G = Delta H - T Delta S, where T stands for the temperature in Kelvin; if G is greater than 0, the reaction is non-spontaneous; if 0, there is equilibrium.
- Why is sunlight important for the theory of chemical evolution?
- Energy from photons can break molecules apart by knocking electrons out of the outer shell of atoms.
- Free Radicals
- The resulting atoms, which have unpaired electrons and are extremely unstable.
- What 2 things can speed up reaction times?
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1. Higher temperature
2. Greater concentration - Explain the difference between reducton and oxidation.
- Reduction is the gaining of an electron and oxidation is the loss of an electron; OIL RIG --> Oxidation is loss, Reduction is gain (often adding/losing Hs)
- Why does water have such a high specific heat?
- It takes an extraordinarily large amount of energy to break the hydrogen bonds.
- Specific Heat
- The amount of energy required to raise the temperature of a substance by 1 degree Celcius
- Explain the difference between acids and bases
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Acids give up a proton during chemical reactions; Bases acquire a proton during chemical reactions
PH is determined by -log[H+] - Air (dry)
- 1.01
- Aluminum
- .90
- Cooper
- .39
- Gold
- .13
- Iron
- .45
- Mercury
- .14
- Table Salt
- .86
- Water (s)
- 2.03
- Water (l)
- 4.18