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
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