Download Chap 2.1 Notes - Nature of Matter

Chap 2.1 Notes - Nature of Matter
Matter – is anything that has mass and takes up space. The
basic unit of matter is the atom.
Structure of the atom
Nucleus – center of the
atom. Contains:
Yellow (+) : proton
Red (0) : neutron
Electron Shells – space
around nucleus where
electrons travel.
Blue (-) : electrons
-
Nitrogen (N)
Elements – are pure substances whose atoms all have the same
number of protons.
The atomic number of an element is equal to the number of
protons in its atoms.
The atomic mass of an element is a sum of the protons and
neutrons in the nucleus of the atoms of that element.
Some elements have isotopes – atoms of the same element with
differing numbers of neutrons.
Atoms are most stable when the outer electron shell is filled. If
this shell is not filled then the atom will undergo bonding to form
a compound.
Compound – substance composed of atoms of different elements
that are chemically combined. Ex. H2O
Characteristics of compounds
1) Proportions of atoms are fixed
H2O (water) = 2 hydrogen atoms: 1 oxygen atom
H2O2 (peroxide)= 2:2 ratio of atoms
2) Properties of compound differ from the elements that
compose it.
Ex. NaCl – Sodium; Chlorine
Bonding – is chemical reaction between atoms to create
compounds.
2 Types of Bonding
1) Covalent – the sharing of 1 or more pairs of electrons
between two atoms.
2) Ionic – attractions between oppositely charged
ions – involves the gain or lose of electrons.
Chap 2.2 Notes – Water, Mixture, and pH
 70 – 95% of an organism’s mass is water.
 Metabolism tends to occur in a water (aqueous) solution.
Structure of Water and Its Polarity
Oxygen – blue – partial negative
charge
Hydrogen – Red – partial
positive charge
H and O are covalently bonded. In water – oxygen is “selfish”
and does not share its electrons equally with hydrogen.
Because of this - water is a polar compound - the molecule has
an uneven electrical charge.
Ex) Water acts like magnet with a “+” and “-“ pole.
+
When two water molecules get close together, a weak attraction
occurs called a hydrogen bond.
Properties of Water
1) Cohesion – water “sticks” to other water molecules.
2) Adhesion - Water can also be attracted to solid surfaces
3) High surface tension – water has a force at its surface. ex)
water bug
4) Expands when it freezes – solid water is less dense and floats.
5) Universal solvent – dissolves ionic and polar substances
Mixtures
Substances that do not bond chemically and are physically
separable are called mixtures.
Ex) salt/sand; lead/iron; salt water
Salt water is an example of a solution, a mixture in which one
substance evenly distributed in another.
Solute – salt – being dissolved by water.
Solvent – water - doing the dissolving.
Water is the UNIVERSAL SOLVENT!
pH- Acidity or alkalinity
pH – is a measure of the acidity or alkalinity of a solution.
1
7
Acids
14
Bases
Neutral
Acid – is a substance that produces hydrogen ions (H+) when
dissolved in water.
Base - is a substance that produces hydroxide ions (OH-) when
dissolved in water.
Chapter 2.4 - CHEMICAL REACTIONS and ENZYMES
Chemical reaction – a process that changes one set of chemicals
into another.
All the Chemical reactions that occur in organisms are known as
the organism’s metabolism. Ex) digestion, cellular respiration,
photosynthesis, etc.
Chemical reactions are summarized using chemical equations
that include the reactants and products. Also chemical
equations must be balanced due to the law of conservation of
matter.
Ex) 6CO2 + 6H2O
Reactants
C6H12O6 +
6O2
Products
Types of reactions include:
1) Synthesis – building new compounds
2) Hydrolysis – aka decomposition – breaking down
3) Replacement/displacement – swapping of “partners”.
4) Combustion
Energy in Reactions
Chemical reactions involve changes in energy.
1) Some reactions require energy and do not occur
spontaneously.
2) Others release energy and occur spontaneously.
Even spontaneous reactions require an input of a small amount
of energy initially. This is called the activation energy.
Enzymes
Enzymes are proteins that act as catalysts for chemical
reactions.
They lower the required activation energy and help speed up the
rate of the reaction.
Enzymes have a specific site that fits to the substrate
(reactants) in the reaction. This site is called the active site.
See the Enyzme/Substrate Complex