Biology Midterm

acid

a compound that donates hydrogen (H+) ions to an aqueous solution, and measures less than 7 on the pH scale

acid precipitation

includes rain, snow, or fog with a pH below 5.6

atom

the smallest unit of matter that retains the properties of an element

matter

includes anything that occupies space and has mass

element

a pure substance that cannot be broken down into other substances by chemical or physical means

trace element

a type of element that is critical to human health, and yet it makes up less than 0.01 percent of human body

molecule

formed when two or more atoms are held together by covalent bonds

polar molecule

a molecule in which opposite ends have opposite electric charges

compound

a substance containing two or more elements chemically combined in a fixed ratio, such as water (H2O)

ionic compound

a compound formed by the attractions of oppositely charges ions such as sodium ions (Na +) and chloride ions (Cl-) to form NaCl (Sodium chloride)

electron

a subatomic particle with a single unit of negative electric charge and is found orbiting the nucleus of the atom

electron shell

the specific area around the nucleus of an atom where electrons may be found

valence shell electrons

electrons found in the outermost shell of the atom

nucleus (of an atom)

the central core that contains the protons and neutrons

proton

a subatomic particle with a single unit of positive electric charge, and is located in the nucleus of an atom

neutron

a subatomic particle that has no charge (electrically neutral), and is located in the nucleus of an atom

atomic number

unique for each element, and is equal to the number of protons in an atom's nucleus

atomic mass

indicates the mass of an atom, which is equal to the number of protons plus the number of neutrons in a given atom's nucleus

isotope

one of several forms of an element, each containing the same number of protons in their atoms but a different number of neutrons

radioactive isotope

an isotope in which the nucleus decays (breaks down) over time, giving off radiation in the form of matter and energy

covalent bond

a chemical bond that forms when two atoms share electrons

hydrogen bond

a unique type of bond created by the weak attraction of a slightly positive hydrogen atom to a slightly negative portion of another molecule

base

a compound that removes hydrogen (H+) ions from an aqueous solution, and measures more than 7 on the pH scale

buffer

a substance that maintains a fairly constant pH in a solution by either accepting hydrogen (H+) ions when their levels rise, or by donating hydrogen (H+) ions when levels fall

ionic bond

a chemical bond that occurs when an atom transfers an electron to another atom

adhesion

the tendency of unlike molecules to stick together (water molecules to molecules in glass)

surface tension

the measure of how difficult it is to stretch or break the surface of a liquid

ion

an atom that has become electrically charged as a result of gaining or losing an electron(s)

polar covalent bond

a type of covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive

cation

positively charged ion

anion

a negatively charged ion

aqueous solution

a solution in which water is the solvent

solute

the substance in a solution that is dissolved and is present in a lesser amount

solvent

the substance in a solution that dissolves the other substance and is present in greater amount

thermal energy

the total amount of energy associated with the random movement of atoms and molecules in a sample of matter

temperature

the measure of the average energy of random motion of particles in a substance

cohesion

the tendency of molecules of the same kind to stick to one another (water molecules to water molecules)

solution

a uniform mixture of two or more substances

chemical reaction

involves the breaking of old chemical bonds and the formation of new chemical bonds that result in new substances

pH scale

a range of numbers used to describe how acidic or basic a solution is, and ranges from 0 (most acidic) to 14 (most basic)

single covalent bond

a type of covalent bond in which two atoms share one pair of electrons - symbolized by a single line between the bonded atoms

reactant

the starting material for a chemical reaction

product

the material created at the end of a chemical reaction

chemical equation

a convenient way to describe a chemical reaction by indicating the reactants (left side), the products (right side), and the chemical formulas of both reactants and products (on both sides)

double covalent bond

a type of covalent bond in which two atoms share two pairs of electrons - symbolized by a pair of lines between the bonded atoms

electronegativity

refers to the attraction of a given atom for the electrons of a covalent bond

nonpolar covalent bond

a type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity

salts

compounds resulting from the formation of ionic bonds and are known a ionic compounds

triple covalent bond

a type of covalent bond in which two atoms share three pairs of electrons - symbolized by a three lines between the bonded atoms

subatomic particles

three types of these that make up all atoms; protons, neutrons, and electrons

Group

shows how many valence electrons an element has

period

shows how many electron shells an element has

75

cells consist about \___% water

92

There are \___ elements in nature

Physical Properties

things that can be observed without changing the identity of the substance

Chemical Properties

things that cannot be observed without changing the identity of the substance

25

\___ elements are essential for human life

oxygen, carbon, hydrogen, nitrogen

These FOUR elements make up about 96% of body weight

carbon, hydrogen oxygen

Carbohydrates contain

carbon, hydrogen oxygen

Lipids (fats) contain

carbon, hydrogen, oxygen, nitrogen, sulfer

Proteins contain

carbon, nitrogen, oxygen, hydrogen, phosphorus

DNA contains (elements)

iron, iodine, fluoride

trace element examples

Molecule

atoms held together by covalent bonds

4

Water molecules can hydrogen bond to \___ partners.

6CO2+6H2O-\>C6H12O6+6O2

Chemical reaction of photosynthesis and cellular respiration

Capillary action

the term for when trees pull water upwards against gravity to get it to their leaves

broken

to raise the temperature of water, hydrogen bonds must be \___ so the molecules can move faster.

released

Heat is \_____ when hydrogen bonds form.

absorbed

Heat is \______ when hydrogen bonds break.

hydrogen bonds

water is more dense as a liquid than as a solid because of \___.

water

the universal solvent

Activation energy

the amount of energy needed to start a chemical reaction

4

A carbon atom can make \___ bonds

hydrocarbon

A carbon compound that includes hydrogen

HCO 3-

The ion that acts as a buffer in blood

water

Carbon dioxide reacts with \___ to form an acid

iodine

trace element that is needed for proper thyroid function

fluorine

trace element that prevents tooth decay

protons and neutrons

the nucleus of an atom contains

protons

determine the element

attraction due to opposite charges

keeps electrons near the nucleus

radioactive isotopes

the movement of atoms in a chemical reaction can be traced by...

2

the innermost shell of an atom has \___ electrons

anion

an atom that gains an electron

become more stable, fill their valence shells, and obtain an electron configuration like a noble gas

atoms form ionic bonds to...

very electronegative

oxygen is...

never

Hydrogen \___ forms ionic bonds

polar

water molecules are...

hydrogen bonding

cohesion is caused by...

breaking of hydrogen bonds

in water, state changes require...

hydrogen bonds

qater's high specific heat and high heat of vaporization are the result of

10

ph 5 is \___ times more acidic than ph 6

acidic

ph 5 is 10 times more \___ than ph 6

decreases

pH \___ as H+ increases

dissociation

the process of a few water molecules breaking apart into ions

H2O--H+OH-

formula for dissociation

ph of 7

in water, a balance of hydrogen (H+) and hydroxide (OH-) equals...

14

pH scale ranges from 0 to \___

basic

14 on the pH scale is the most \___