Glossary of Liberty Concurrent Credit Biology Chapter 2

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What is matter?
Any substance that has mass and occupies space.
What are atoms?
Extremely small particles of matter.
What are electrons?
Tiny subatomic particles that orbit around the nucleus of an atom that carry a negative charge.
What are protons?
Subatomic particles located in the nucleus of an atom that carry a positive charge.
What are neutrons?
Subatomic particles located in the nucleus of an atom that carry no charge.
What is atomic number?
The number of protons in an atom of a certain element.
What is the difference between mass and weight?
Mass measures the amount of matter in a substance. Weight measures the force of gravity in a substance.
What is atomic mass?
Atomic mass is the number of protons and neutrons an atom has.
What is the unit of measure for atomic mass?
The dalton.
What is an element?
Atoms with the same atomic number.
What is an isotope?
An atom of an element that has different number of neutrons.
What are radioactive isotopes?
Isotopes whose nucleus decay and emit radioactive energy.
Why are radioactive isotopes important?
They can be used to establish timelines in biology and geology.
What is half-life?
The time it takes for half of a sample of radioactive isotopes to decay.
What are neutral atoms?
Atoms with the same number of protons and electrons.
How do electrons maintain their orbit around the nucleus?
By attraction to the positive charge of the nucleus.
What are ions?
Atoms in which the number of protons doesn't equal the number of electons.
What is a cation?
An ion with a net positive electrical charge.
What is an anion?
An ion with more electrons that protons that carries a net negative electrical charge.
What is an orbital?
The area aroud a nucleus where an electron is likely to be found.
Why do electrons determine the chemical behavior of atoms?
Because they are located relatively far away from the nucleus, atoms are made of mostly empty space. This prevents protons from being involved directly in chemical reactions, and puts the oness on the electrons.
What is energy?
The ability to do work.
What is potential energy?
The energy of position.
Why is potential energy important in chemical reactions?
Because electrons have potential energy, the further they are away from the nucleus, the more energy they have, the more energy they require to leave the orbital.
What is reduction?
The gain of an electron in a chemical reaction.
What is oxidation?
The loss of an electron in a chemical reaction.
What is important about potential energy in redox reactions?
An electron keeps its potential energy in a redox reaction.
What's the difference between an energy level and an orbital?
An orbital refers to the likely location of an electron relative to the nucleus. The energy level refers to the amount of energy that the electron has.
How many naturally occuring elements are there?
What are valence electrons?
Electrons in the outer energy levels of an atom.
What are inert elements?
Elements whose outer energy level have all eight electrons in them.
What is the octet rule?
Atoms tend to establish completely full outer energy levels.
How many elements are found in significant amounts in living things?
What is a molecule?
A group of atoms held together by a stable association.
What is a compound?
A molecule that contains atoms of more than one element.
What is a chemical bond?
The force that joins atoms together in a molecule.
What are ionic bonds?
Bonds formed by atoms of opposite electrical charges.
What is an ionic compound?
A compound formed by ionic bonds.
What are covalent bonds?
Bonds formed when atoms share one or more pairs of electrons.
Why are covalent bonds stong?
They have no net charge. The octet rule is satisfied. They have no free electrons.
What are double bonds?
Covalent bonds where atoms share two pairs of electons.
What are triple bonds?
Covalent bonds where atoms share three pair of electrons.
What are structural formulas?
Formulas for molecules that pictorially represent their covalent bonds.
What are molecular formulas?
Formulas that indicate the types and numbers of atoms in a molecule.
Why can large molecules be formed by covalent bonds?
Because certain atoms may be able to share electrons with more than one atom.
What is a chemical reaction?
The formation and/or destruction of chemical bonds.
What is a reactant?
Molecules before the start of a chemical reaction.
What are products?
Molecules after the chemical reaction.
What factors affect the extent to which a chemical reaction can occur?
Temperature. Concentration of reactants and products. Catalysts.
What role did water play in the formation of life?
When life was originating, water provided a medium in which other molecules could move around and interact without being held in place by strong covalent bonds.
What is the most important chemical property of water in relation to biology?
Its ability to form hydrogen bonds.
What is electronegativity?
The force of attraction of the electrons in a covalent bond.
Where are the shared electrons in a water molecule more often located?
Orbiting around the oxygen atom.
What is a tetrahedron?
The "mickey mouse" shape of the water molecule -- the hydrogen for the ears and the oxygen forms the head.
What is a polar molecule?
A molecule with a positive partial charge at one end and a negative partial charge at the other.
What is a hydrogen bond?
The bridging of an hydrogen ion or the positive partial charge of a polar molecule to the negative partial charge of a water molecule.
If hydrogen bonds are individually weak, why are they important?
Because they have a cumulative effect, like Velcro. One hook and loop isn't going to hold anything, but get a bunch of them together and you can hold up a lot of stuff.
What is cohesion?
When the opposite polar sides of water molecules are attracted to each other.
What is adhesion?
When one polar side of a water molecule is attracted to an oppositely charged object.
What is surface tension?
The cohesion of water molecules at an air-water interface.
What is capillary action?
The adhesion of water molecule to a substances having a surface charge.
How does water moderate temperature?
High specific heat and high heat of vaporization.
What is specific heat?
The amount of heat that must be absorbed or lost by 1 gram of a substance to change its temperature by 1 degree Celsius.
What's important about water's high specific heat?
Because of its high specific heat, water heats up more slowly than most compounds and holds its temperature when no heat is applied.
What's heat of vaporization?
The amount of heat energy required to change 1 gram of a substance to a gas.
What is a hydration shell?
When water molecules surround an ion or charged molecule to prevent it from associating with any other molecule.
What are hydrophobid molecules?
Molecules that shrink away from contact with water.
What are hydrophilic molecules?
Polar molecules that readily form hydrogen bonds with water.
What is hydrophobic exclusion?
The tendency of nonpolar molecules to collect away from water.
What happens when water ionizes?
It spontaneously splits to form a hydrogen ion [H+] and a hydroxide ion [OH-].
What is a mole?
The weight in grams that corresponds to the summed atomic masses of all the atoms in a molecule.
What is molar concentration?
The amount of moles per liter of a substance.
What is pH?
The negative logarithm of hydrogen ion concentration in a solution: pH = -log [H+]
What is an acid?
Any substance that dissociates in water to increase the concentration of hydrogen ions.
What is a base?
A substance that combines with hydrogen ions when dissolved in water, thus lowering the concentration of hydrogen ions.
What is a buffer?
A substance that acts as a reservoir for hydrogen ions, donating them when their concentration falls and taking them when their concentration rises.
Why are buffers important?
Because they help organisms maintain a relatively constant pH level.

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