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Chapter 2
The Chemistry of Life
The Chemistry of Life
• Matter- anything that has mass and takes
up space
– Solid: any substance that has a definite shape
and a definite volume
– Liquid: has a definite volume but no definite
shape
– Gas: has no definite volume or shape
*Changing states requires adding or removing
energy
Physical Changes
• A physical change is a change in the size,
shape, or state of a substance
– Ex: melting, freezing, molding clay, cutting wood
Atoms
• Atoms- the smallest particles that make up
all matter
– Protons(+): positively charged particles found
in the nucleus of an atom
– Neutrons(o): neutral particles found in the
nucleus of an atom
– Electrons(-): negatively charged particles
found outside of the nucleus
Model of the Atom
Elements
• Elements are substances made of only one
type of atom
– Ex: O2(oxygen)
H2(hydrogen)
O3(ozone)
Ions
• Ions are atoms that have lost or gained
electrons
• Ions have a positive(+) or negative(-) charge
Lose
Na
Electron
Na
+
Positive ion
_
Gain
Cl
Electron
Cl
Negative ion
Compounds & Molecules
• Compounds and Molecules are formed
when 2 or more different elements are
bonded together
• Ex: Compound- Salt(NaCl)
Molecule- Water(H2O)
Molecular Formulas
• Molecular formulas show the kind and # of
atoms in a molecule
– H2O = 2 hydrogen atoms + 1 oxygen atom
– CO2 = 1 carbon atom + 2 oxygen atoms
– C6H12O6 = 6 carbon atoms + 12 hydrogen atoms
+ 6 oxygen atoms
– NaCl = 1 sodium ion(Na) + 1 chlorine ion(Cl)
Chemical Change
• Chemical change occurs when atoms combine or
separate to create new substances
• Chemical changes use or give off energy
• Ex: Combustion(burning)
C3H8 + O2

CO2
+ H2O
propane + oxygen  carbon dioxide + water
• Ex: Oxidation(rusting)
Fe + O2  Fe2O3
iron + oxygen  ironoxide(rust)
Mixtures
• A mixture forms when chemicals combine but do
not bond
– Ex: salt water, salad dressing, chocolate milk
• Solutions: is a mixture with it’s parts evenly
mixed
Solute – substance that gets dissolved
ex: salt, sugar, chocolate
Solvent – substance that dissolves another substance
ex: water, milk, alcohol
Bonding
• Bonding is a force of attraction holding
atoms together
• Types of Bonding:
– Covalent Bonds
– Ionic Bonds
– Hydrogen Bonds
Covalent Bonds
• Covalent bonds form when 2 or more
neutral atoms share electrons to form a
molecule
– Ex: H2O(water)
-Ex: CO2(carbon dioxide)
Ionic Bonds
• Ionic bonds form when 2 or more ions
become held together by their opposite
charges
• Ex: NaCl(salt)
– Positive ions are
attracted to negative ions
Hydrogen Bonds
• Hydrogen bonds hold together water
molecules
Cohesion & Adhesion
• Cohesion- the attraction between molecules
of the same kind
– Ex: water forms droplets, surface tension
• Adhesion- the attraction between different
substances
– Ex: water drops stick to leaves and skin
Cohesion & Adhesion
Acids & Bases
• Acids- contain large amounts of
hydrogen(H+) ions
– Acids turn pH paper RED
Ex: stomach acid(HCl), vinegar, citric acid
• Bases- contain large amounts of
hydroxide(OH-) ions
– Bases turn pH paper BLUE
Ex: bleach, ammonia, soap
Neutral Substances
• Neutral substances have equal amounts of
hydrogen(H+) and hydroxide(OH-) ions
Ex: water (H2O), alcohol (C2H5OH), oil
- neutral substances do not change pH paper
Types of Compounds
• Inorganic- come from non-living things, do not
contain carbon
Ex: Salt (NaCl) – sodium chloride
Water (H2O)
• Organic- come from living things and contain
carbon
Ex: Carbohydrates, Fats, Proteins, Nucleic Acids
Carbohydrates
• Used for Short Term energy
• Contain: carbon(C), Hydrogen(H), oxygen(O)
• Ex: sugars- glucose, sucrose, fructose
starches- bread, pasta, potatoes
Glucose - C6H12O6
Fats & Lipids
• Used for Long Term energy storage
• Contain: carbon(C), hydrogen(H), oxygen(O)
• Ex: fats, oils, waxes
Proteins
• Used to Build and Repair body tissues
• Contain: carbon(C), hydrogen(H), oxygen(O), &
nitrogen(N)
• Proteins are made from amino acids
Nucleic Acids
• Used to make DNA
• Contain: carbon(C), hydrogen(H), oxygen(O),
nitrogen(N), & phosphorus(P)
Enzymes
• Enzymes are a special type of protein used
to perform chemical reactions within the
body
• Certain enzymes build new molecules and
others break down molecules within the
body
Enzymes
• Enzymes bind to a substrate with a
matching active site
END OF
CHAPTER 2 NOTES!!!