BMB 207 umaine

1st law of thermodynamics (law of conservation of energy)

Energy cannot be created or destroyed just converted from one form to another. It is converted in isolated systems.

Energy

the ability to do work - comes in many different forms. Different forms can be interconverted.

An "extensive" property of a system - it is dependent on the size of the system

Kinetic energy

K.E = 1/2mv^2

It's the energy of motion. Depends on mass and velocity

Potential energy

the energy an object has that is due to its position

2nd law of thermodynamics

in any naturally occurring process, some energy is lost in an unusable form

Thermal Energy

Atoms are always in motion and the random kinetic energy of atoms equals thermal energy.

It depends on the amount of substance while the temperature does not

Heat and heat normally produce a change in temperature of substance.

Heat

mass * temp change * specific heat

Specific Heat

conversion factor that allows us to translate temperature changes into the corresponding environment.

It is an INTENSIVE property like density. Each substance has it's own characteristic specific heat.

Specific heat of water

1 cal/gx degrees C

The specific heat of water is relatively high compared to most substances. Water can absorb a high amount of heat energy without having an abnormal high temp rise as result.

Water is an effective temperature buffer

Buffer

Substance that declines or modifies the effect of a change in a physical parameter

Kilocalorie

Kcal = 1kcal = 1000 cal = 1 Cal

Joule

j = 1 cal = 4.184 j

Kilojoule

kj - 1 kj = 239 cal. = 1 kcal = 4.184 kj

3 states of matter

solid, liquide, gas

Solid

high density. particles remain in fixed positions

Liquids

moderate to high density. particles move about but remain in contact with one another.

Gas

very low density. particles are free to move throughout container. as temperature of gas increases, the volume of gas increase and the pressure stays the same.

How do you change something into a gas?

the thermal energy and kinetic energy of atoms must increase

How do you change something to a solid

thermal energy and kinetic energy of atoms must decrease

Pressure

the force applied on a surface divided by the area of the surface.

as temperature of gas increases, the pressure of gas increases if volume stays the same

Low temp

collisions are infrequent and gentle = LOW pressure

High temp

collisions are frequent and forceful = HIGH pressure

Partial pressures

In a gas mixture, the pressure that each gas exerts is called the partial pressure of a gas.

Dalton's Law of partial pressure

states that the pressures of the individual gases in any mixture add up to the total pressure of the gas mixture.

Changes of state

Chemical structure of water molecules doesn't change in transfer of state. What changes is the degree to which water molecules interact with one another.

Boiling Point

the temperature at which liquid boils

Heat of fusion

amount of heat required to melt 1 gm of a solid substance

Vaporization

heat required to boil 1 gm of liquid

Heating curves

cause temperature changes. Phase changes occur at constant temp.

The state of a substance

at any temperature is a balance between attraction of particles to 1 another and the thermal energy of the particles which associate the particle.

physical properties like melting and boiling point and density are determined by kinetic energy of particles and their attraction for one another

What do covalent bonds strength depend on?

depend on the nature of the constituent atoms and the "order" of the bond

Making/Breaking bonds

Making bonds releases energy from the system, breaking bonds requires input of energy into the system

Ion-Ion Attraction

As result of strong attraction between positive and negative ions, all ionic compounds are solids at room temperature. In general it takes very high temperatures to melt ionic solids

All Ionic Compounds - very strong

Dipole-Dipole Attraction between Polar Molecules

Molecules that contain polar bonds attract one another more strongly than non-polar molecules because the expositive charged atom in 1 molecule attracts negatively charged neighbor atoms.

Attraction of molecules with polar bonds = dipole-dipole attraction

Molecular compounds contains polar bonds - weak

Dispersion Forces

All molecules are attracted to 1 another because the electrons of each molecule are attracted to protons of nuclei of nearby molecules.

Non-bonding interactions between molecules which are virtually in contact. Most important effect seen with non polar molecules.

All molecular compounds = weak = increases size of molecules

H Bonding

Any molecule that contains O-H or N-H covalent bonds will form H bonds

It's not directly related to the covalent bonding of H atoms in compounds.

Attraction between the positive charged H and negative charged O is called H Bond

H Bond can be special Dipole-Dipole interaction between an H bonded to O or N and a non-bonded electron pair

Molecular compounds containing O-H or N-H weak

Physical Properties of water

high boiling point for size.

high specific heat = good heat buffer

polar = dissolves polar and charged molecules

high internal cohesion - surface tension

Ice floats - less dense than water = good for fish in winter

What does each water molecule have?

2 dipoles due to partial separation of charges. Each water molecule acts as H bond diner and H acceptor = excessive H bonding in bulk water

What does each ice molecule have?

Each water molecule makes 4 H bonds with 4 surround water molecules

Solutes Disturb Water Structure

H bonds in water = broken

regular input of energy - system is less stable

What do Hydrocarbons and other non polar molecules form?

NO compensating interaction with water to compensate for the negative entropy change

Electrolytes and Dissociation

Solution of electrolytes in water = conductive

To conduct electricity, solute must form ions when it dissolves in water. This is dissociation.

What do charged species do?

Interact with water dipoles to form many weak interactions. Many weak interactions are made that release energy.

Nonelectrolytes

Can dissolve in water but aren't conductive

When a molecular compound dissolves, molecules move away from one another but don't break into ions

Many molecule solutes are nonelectrolytes

Solubility

The upper limit to the mass that can be dissolved in a liter of water is the solubility of a substance

Unsaturated solubility uses less that this amount of solute and could dissolve more solute

Solubility of solids in water does what?

Increases as you raise them

Do gases dissolve better in cold or hot water?

Cold

COOH groups

Ionic and are either fully or partially charged when in an aqueous solution

Solid and Weak bonding

the more weak interactions with water that a molecule can form = higher solubility

The more non-polar groups a molecule contains = less solubility

S orbitals

spherical and surround the nucleus

P orbitals

shaped like a double lobed teardrop and are located along a coordinate axis at 90 degrees from each other

Atomic Shell 1

Has 1 subshell = 1 s subshell has 1 orbital holding 2 electrons

Atomic Shell 2

Has 2 subshells - the 2s subshell has 1 orbital which holds 2 electrons.

the 2p subshell has 3 orbitals which holds 6 electrons

Atomic orbitals combine to form what?

Molecular orbitals. 2 atomic orbitals forms 2 molecular orbitals.

Bonding Molecular Orbital

New orbitals.

Bond Energy

the energy released upon bond formation

Single bond

1 pair of shared electrons

Negative

high electron density on oxygen

Positive

low electron density on hydrogen

IUPAC

International Union of Pure and Applied Chemistry

Provides rules for systematic namings of chemical compounds

1) write the name of the least electronegative atom 1st

2) write the name of the 2nd element replacing the suffix with "ide"

So3

Sulfur trioxide

N2O5

Dinitrogen Pentoxide

NH3

Ammonia

Chlorine Dioxide

ClO2

Iodine Monobromide

IBr

Why don't groups 1A and 11A generally form covalent bonds?

the sodium atom only has 2 electrons in its valence shell

Ionic Compounds

formed as a result of transfer of one or more electrons from an electron diner to an electron adaptor which is more electronegative. Usually satisfies valences and octet rule

Soluble in strong polar solvents such as water but this isn't always the cure and prediction solubility is sometimes comp.

Polyvalent Ions

Atoms can gain or lose more than 1 electron

Atoms with 1 2 or 3 valence electrons can satisfy the octet rule by losing all of their valence electrons

Balancing Formulas of Ionic Compounds

Rule of charged balance for an ionic compound is total amount of positive charge must equal total amount of negative charge

Naming Binary Covalent Bonds

1) Determine if compound is covalent or ionic

2) Name least electronegative atom 1st with proper prefix to describe how many are present

3) Name most electropositive atom 2nd with proper prefix and suffix

*Be sure to give the simplest possible ratio for ionic compounds*

Naming Ionic Compounds

Metal (Cation) name + Non-Metal (Antion) stem + ide

Naming Compounds with Transition Metals

Roman numerals or suffixes added to stem words are used to indicate the charge on the transition metal

"ous" is added to the stem for the lower possible charge of a transition metal

"ic" is added to the stem for the higher possible charge of transition metals

The charge on the ion of most transition metals usually cannot be predicted and most transition metals can form more than 1 charge

No di, tri etc needed with ionic compounds

Polyatomic Ions

monoatomic ions are made of one ion

Polyatomic ions are ions made up of more than one atom

Ionic Compound Facts:

Ionic Bonds

Formula starts with a metal or with NH4 (ammonia)

Name the cation and then the anion

No di, tri, etc

Molecular Compound Facts:

Covalent bonds

Contains only nonmetals and no NH4

Name elements in order they appear in the formula

Use di, tri, etc to tell how manny atoms of each elements are present