BIOLOGY CH 2Chemistry of Life

MATTER Matter is anything that occupies space and

has mass Mass is the quantity of matter an object has Weight is the force produced by gravity

acting on mass, not the same as mass Chemical changes in matter are part of all

life processes Biologists study chemistry because all living

things are made of matter just like nonliving things

ELEMENTS Elements are substances that cannot be

broken down chemically into simpler kinds of matter

Around 30 elements are associated with life Carbon Oxygen Hydrogen Nitrogen

PERIODIC TABLEElemental information is collected

on the Periodic TableEach element is represented with a

chemical symbolA chemical symbol is a 1-3 letter abbreviation

The symbol either comes from the current or the Latin nameEx. Chlorine = ClEx. Sodium = Na

ATOM An atom is the

simplest particle of an element that is still an element The central region of

an atom is the nucleus A proton is a

positively charged subatomic particle in the nucleus

A neutron is a neutral subatomic particle in the nucleus

ATOMIC AND MASS NUMBERS The atomic number tells the number of

protons in an atom of an element In a stable atom, protons = electrons, so the

atomic number can tell electrons too On the periodic table, the number often appears

above the element symbol The mass number tells the number of

protons + the number of neutrons On the periodic table, the number often appears

below the element symbol

ELECTRONS Small negatively charged particles in an

atom are electrons The number of negative electrons equals the

number of positive protons, so a stable atom is neutrally charged (net charge)

Electrons move about the nucleus at high speeds in orbitals

An orbital is a 3D region around a nucleus that is a probable location of an electron

Energy level decreases with each orbital farther away from the nucleus

All orbitals combined produce an electron cloud

ISOTOPES All atoms of an element have the same

number of protons All atoms do not always have the same

number of neutrons Atoms of the same element that have a

different number of neutrons are called isotopes

COMPOUNDS Naturally, elements do not exist alone, they

combine with the same element or other elements to form compounds

Compounds are made of atoms of 2+ elements in fixed proportions Ex H2O

Elements combine when their outer electron orbitals are not full

Compounds form when a chemical bond is created between two elements’ unfull outer electron orbitals

Noble gases on the periodic table are full and stable and do not form compounds

COVALENT BOND A covalent bond forms when 2 atoms share

1+ pairs of electrons Ex. Hydrogen needs 2 electrons in its outer

orbital to be stable and oxygen needs 4. So with 1 oxygen and 2 hydrogen, each are stable

MOLECULE A molecule is the simplest part of a

substance that retains all of the properties of that substance and can exist alone

All molecules share covalent bonds.

IONIC BOND An ionic bond forms when 2 atoms gain and

lose electrons to form a compound Again, the outer orbitals will not be full and

looking for stability (more/less electrons) An atom that is unbalanced and charged is

an ion An atom with more protons than electrons is a

positive ion, cation An atom with more electrons than protons is a

negative ion, anion

BIOLOGY CH 2Energy

ENERGY Energy is the ability to do work Energy can exist in many forms

Electrical energy Chemical energy Thermal energy Energy of Motion

Inside living organisms energy is converted from one form to another Ex. After eating a meal, the chemical energy in

food is changed to thermal, mechanical, etc. energy

STATES OF MATTER All atoms and molecules in all matter are

moving The motion of the atoms/molecules, and the

spacing between them, determining a substance’s state Solid Liquid Gas

STATES OF MATTER Solid substances will have a fixed shape and a

fixed volume Solid substacne atoms will move less than other,

they will only vibrate A liquid has a fixed volume but no fixed shape

Liquid substances will move more freely but the atoms will simply roll around one another

Gas substances have no fixed volume and no fixed shape Gas substance atoms move rapidly with little

contact; they will fill their space Thermal energy (heat) must be applied to/taken

away from a substance for it to change states

ENERGY TRANSFER Living things are carrying out many chemical

reactions each day (metabolism) In a chemical reaction, 1+ substances

change to produce 1+ different substances Chemical reaction can either continue to

completion or reach a state of equilibrium Energy is absorbed or released when

chemical bonds are broken or formed Reactants are the substances present before the

chemical reaction Products are the substances after the chemical

reaction

ACTIVATION ENERGY Energy must be added for most reactions to

begin The amount of energy needed to start a

reaction is the activation energy For most reactions, this amount (activation

energy) is large Catalysts reduce the activation energy

needed and help the reaction to proceed An enzyme is a protein that speeds up

metabolic reactions without being permanently changed or destroyed

REDOX REACTIONS Many reactions that transfer energy in living

things transfer electrons Reaction in which electrons are transferred

between atoms are redox reactions An oxidation reaction occurs when a reactant

loses 1+ electrons (more positive) A reduction reaction occurs when a reactant

gains 1+ electrons (more negative) Oxidation and reduction reactions always occur

together