Chapter 4 Biology Quiz

how water moderates temperatures on earth

stabilizes air temperatures by absorbing heat from warmer air and releases relatively large amounts of heat with only a slight change in its own temperature.

hydrophobic

substances that have no affinity for water

cohesion

when water molecules are bonded to their neighbors creating a high level of structure. this plays a key role in the transport of water against gravity in plants

ice

when water reaches 0 degrees celsius water becomes locked into a crystalline lattice with each molecule bonded to the maximum of four partners. therefore its structure makes it float

octet rule

where the outer shell has to have eight valence electrons. this happens with every other atom except for hydrogen

secondary rule

where the outer valence electron is filled with only two electrons

hydrogen bonds description

within a cell, weak, brief bonds between molecules are important to a variety of processes. these are weak interactions

evaporative cooling

as a liquid evaporates the surface of the liquid that remains behind cools. this occurs because the most energetic molecules are the most likely to evaporate, leaving the lower kinetic energy molecules behind

water

as ice starts to melt some of the hydrogen bonds break and some water molecules can slip closer together than they can while in the ice state

celsius scale

at seal level water freezes at 0 degrees and boils at 100 degrees. human body temperature averages 37 degrees

isotopes

atoms of the same element that differ in the number of neutrons

basic on how atoms bond

atoms with incomplete valence shells interact by either sharing or transferring valence electrons

anions

atoms with negative charges

cations

atoms with positive charges

element

is a substance that cannot be broken down to other substances by chemical reactions

acid precipitation

it occurs when rain, snow, or fog has a pH that is more acidic than 5.6. caused by sulfur oxides and nitrogen oxides in the atmosphere.

water chemistry

most cells are about 80% water

reading the pH scale

neutral solutions are 7. acidic solutions have values less than 7 and basic solutions have values more than 7

protons

one unit of a positive charge and makes up the atomic nucleus at the center of the atom. 1 dalton

hierarchy of structural levels

organism level, organ system level, organ level, tissue level, cellular level, molecular level, and atomic level

molecule

two or more atoms held together by covalent bonds constitute this

pH scale

used to describe how acidic or basic a solution is

aqueous solution

water is the solvent

hydrogen valence

1

oxygen valence

2

nitrogen valence

3

carbon valence

4

structural formula

we can abbreviate the structure of this molecule by substituting a line for each pair of shared electrons drawing this....

hydrogen bonds

when a hydrogen atom that is already covalently bonded to a strongly electronegative atom is attracted to another strongly electronegative atom.

valence shells

when atoms bond they need to complete their outer valence electron shell

solution

a liquid that is a completely homogeneous mixture of two ore more substances

water molecule

a polar molecule with opposite ends of the molecule with opposite charges. the polarity results from hydrogen bonding

acid

a substance that increases the hydrogen ion concentration in a solution

comparison of H+ and OH-

adding acid to a solution shifts the balance between H+ and OH- toward H+ and leads to a decline in OH-.

ions

after the transfer both atoms are no longer neutral but have charges

hydrophilic

any substance that has an affinity for water. these substances are dominates by ionic or polar bonds

base

any substance that reduces the hydrogen ion concentration in a solution. they have more OH-

matter

anything that takes up space and has mass.

CHONPS

carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulfur

chemical reactions

chemical bonds are broken and reformed leading to a new arrangement of atoms. all of the atoms in the reactants must be accounted for in the products; they must be balanced

adhesion

clinging of one substance to another

ionic compounds/salts

compounds formed by ionic bonds. they can have ratios of elements different from 1:1

neutrons

electrically charged neutral and makes up the atomic nucleus at the center of the atom 1 dalton

valence electrons

electrons in the valence shell. atoms with the same number have similar chemical behavior.

trace elements

elements required by an organism but only in minute quantities

atoms valence

every atom has a characteristic total number of covalent bonds that it can from this...

electrons

has one unit of a negative charge and forms a cloud around the nucleus. the attractions between the positive charges in the nucleus and the negative charges of the electrons keep the electrons in the vicinity of the nucleus. 1/2000 dalton but we usually ignore the contribution when determining the total mass of an atom. they have potential energy because of their position relative to the nucleus.

surface tension

hydrogen bonds among surface water molecules resist stretching or breaking the surface.

nonpolar covalent bond

if electrons in a covalent bond are shared equally. this always happens between two atoms of the same element. also between atoms that have similar electronegativities

polar covalent bond

if the electrons in a covalent bond are not shared equally by the two atoms. this happens between oxygen and hydrogen because oxygen has a much higher electronegativity than hydrogen does. these bonds have regions that have a partial negative charge near the strongly electronegative atom and a partial positive charge near the weakly electronegative atom.

process of covalent bond

if two atoms come close enough that their unshared orbitals overlap, each atom can count both electrons toward its goal of filling the valence shell

product of H+ and OH-

in any solution the concentration is constant at 10-14. in a neutral solution H+=10-7 M and OH-=10-7. they always have to add up to 14 in some way

molecular formula

indicates the number and types of atoms present in a single molecule

energy

the ability to do work

electronegativity

the attraction of an atom for the electrons of a covalent bond. the strong atoms attempt to pull the shared electrons toward themselves

valence shell

the chemical behavior of an atom depends mostly on the number of electrons in its outermost shell. when it is completed it is unreactive. all other atoms are chemically reactive because they have incomplete valence shells.

orbital

the complex three-dimensional space an electron occupies

energy levels/electron shells

the different states of potential energy that the electrons of an atom can have. the first shell, closest to the nucleus, has the lowest potential energy. electrons in outer shells have more potential energy. electrons can only change their position if they absorb or release a quantity of energy that matches the difference in potential energy between the two levels.

solvent

the dissolving agent

products

the end molecule

potential energy

the energy that matter stores because of it position and location

hydrogen ion

the hydrogen atom that leaves its electron behind and is transferred as a single proton

hydroxide ion

the molecule that lost a proton

hydronium ion

the molecule with the extra proton

atomic number

the number of protons and electrons if not indicated otherwise in each element. all atoms of a particular element have the same number of protons in their nuclei.

covalent bond

the sharing of a pair of valence electrons by two atoms

double covalent bond

the sharing of two pairs of valence electrons

subatomic particles

the smaller parts of an atom that make up the atom. ex. protons, neutrons, and electrons.

atom

the smallest unit of matter that still remains the properties of an element.

reactants

the starting molecules in the process

solute

the substance that is dissolved

atomic mass

the sum of the number of protons and neutrons in the nucleus of an atom. therefore we can determine the number of neutrons in an atom by subtracting the number of protons (the atomic number) from this term

dalton

the unit to measure the mass of subatomic particles

chemical bonds

these interactions typically result in the atoms remaining close together held by an attraction

what do covalent bonds form with

they can form between atoms of the same element or atoms of different elements. while both types are molecules, the latter are also compounds. they have to satisfy the valence of both elements.

ionic bond

this can form if two atoms are so unequal in their attraction for valence electrons that one atom strips an electron completely from the other. because of differences in charge cations and anions are attracted to each other. these atoms need to have not acquired their charge by electrons transferred with each other