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AP Biology Review
Terms in this set (23)
Describe atomic structure, using the terms proton, neutron, electron, atomic number, mass number, atomic weight, valence and orbital. Indicate what is meant by electrons in an "excited state" and those in a "ground state".
An atom is composed of protons (positive charge) and neutrons (neutral) in an atomic nucleus. Surrounding the nucleus are electrons (negative charge), in an electron cloud. Each element has a unique number of protons, called the atomic number, and when added to the number of neutrons, forms a mass number. The atomic weight of an atom is simply the mass number expressed in Daltons. Electrons form in shells, called orbitals, and the farthest one is the valence. When electrons get "excited" and move more, they absorb energy and move to higher orbitals. Then, they lose energy and fall back to their ground state, emitting energy in light.
Explain what an isotope is and give two important physical properties of isotopes that make them useful in biological research. Define half-life.
Each element has a specific amount of protons, but the neutrons in each atom vary, called isotopes. Some isotopes are radioactive, and can thus be used to find out fossil age or can be traced in an organism. A half-life is how long it takes the atom to decay to half of its original mass.
Determine the number of neutrons when given the atomic number and mass number of an atom.
When given the mass number, simply subtract the atomic number to get the number of neutrons.
State the four elements that make up 90% of living matter.
Carbon, Oxygen, Hydrogen, and Nitrogen
Explain how electron configuration influences the chemical behavior of atoms.
The chemical behavior of atoms is based on their electron configuration. Specifically, the outermost/valence shell. This is why atoms with full valence shells are nonreactive.
Define electronegativity and explain how it influences the formation of chemical bonds.
Electronegativity is the attraction an atom has to the valence electrons of other atoms. After receiving electrons, the atoms bond together.
Explain the octet rule and predict how many bonds a specific atom might form.
The octet rule states that the majority of elements form valence shells with 8 electrons. The number of bonds an atom makes depends on the amount of electrons needed to fill the octet rule.
Explain why the noble gases are so unreactive.
Noble gases are so unreactive because their valence shells are full, and they aren't electronegative.
Using diagrams, explain what an ion is, and how it forms. Describe an ionic bond.
Describe a covalent bond and tell how it differs from an ionic bond.
A covalent bond (polar or nonpolar) results from the sharing of electrons. This is different from an ionic bond, in which one electron is completely stripped from one atom and given to another.
Describe the formation of a hydrogen bond and explain how it differs from a covalent or ionic bond.
A hydrogen bond forms when hydrogen is covalently bonded to one atom while also being attracted to another. Covalent and ionic bonds are intramolecular (between atoms of a molecule), while hydrogen bonds are intermolecular (between whole molecules).
Describe the special physical properties of water.
Cohesion: The constant forming and breaking of hydrogen bonds, gives water structure
Adhesion: Water clings to other surfaces, especially polar substances. Allows water to remain in cells.
High Specific Heat: Water requires much energy to raise its temperature. Can store heat while barely warming, regulates temperatures.
Heat of Vaporization: Water has a high heat of vaporization. This causes stable temperatures and relief in humans (sweat) and plants through evaporative cooling.
Density Solid vs. Liquid: Since ice is less dense than liquid water, living organisms can survive under ice in cold temperatures.
Universal Solvent: Waters polarity allows it to dissolve many substances. Allows for cells, blood, saliva, sap, etc.
Draw two water molecules in a way that illustrates a hydrogen bond.
Explain the relationship between the polar nature of water and its ability to form hydrogen bonds.
Since water forms polar covalent bonds made of positively charged hydrogen atoms, they are attracted to all other polar molecules.
Describe the structure and geometry of a water molecule, and explain.
Since water forms countless momentary hydrogen bonds, it always maintains a shape, giving it cohesion.
Describe how water contributes to the fitness of the environment to support life.
Without water and its emergent properties, life on earth would be impossible as cells are mostly water and water is used to carry nutrients, oxygen, etc.
List five characteristics of water that are emergent properties resulting from hydrogen bonding.
Cohesion, adhesion, high specific heat, high heat of vaporization, universal solvent
Explain how water's high specific heat, high heat of vaporization, and expansion upon freezing affect both aquatic and terrestrial ecosystems.
Since water is able to share large amounts of energy, and can store and/or release heat depending on the temperature, it acts as an equalizer and regulates temperatures on earth. The fact that solid ice is less dense than liquid water allows aquatic life to continue under a layer of ice (which acts as a shield from the colder air).
Explain how the polarity of the water molecule makes it a versatile solvent.
Since water is polar in nature, it forms hydrogen bonds with other polar substances, and through hydration shells, dissolves them.
Describe the biological importance of the cohesiveness of water.
The fact that water is cohesive in nature allows it to maintain its shape against the force of gravity by being attracted to polar molecules higher than itself.
Distinguish between heat and temperature.
Heat is a measure of total kinetic energy due to molecular motion in matter. Temperature is a measure of the intensity of heat due to the average kinetic energy.
Explain the basis for the pH scale.
The basis for the pH scale is the amount of H+ and OH- ions in a solution. More H+ ions means a solution is more acidic, while more OH- ions means the solution is more basic.
Explain why buffers are important to living things. Explain how a buffer system works.
Buffers are important to living things because they help to maintain as normal of a pH as possible. All living things function at a pH of around 7, which is neutral and the pH of water. Buffers work by releasing H+ ions during a rise in pH, and taking/absorbing them when there is a drop in pH.
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