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. H
2
O
Characteristics of compounds
1) Proportions of atoms are fixed
H
2
O (water) = 2 hydrogen atoms: 1 oxygen atom
H
2
O
2
(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 14
Acids 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) 6CO
2
+ 6H
2
O C
6
H
12
O
6
+ 6O
2
Reactants 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