The Chemistry of Life

Section 2.1

Atoms

• The basic unit of matter are atoms.

• 100 million atoms would make a row only about 1 cm long!

• Consists of subatomic particles:

- Protons

- Neutrons

- Electrons

Subatomic particles

• Protons- positively charged.

• Neutron- has no charge.

- They form the nucleus of the atom.

• Electrons- negatively charged with 1/1840 the mass of a proton.

- In constant motion in space around the nucleus.

Elements

• A chemical element is a pure substance that consists entirely of one type of atom.

Can you name some?

• The number of protons in an atom of an element is the element’s atomic number.

- Carbon: atomic number 6

- Has 6 protons and 6 electrons

Isotopes

• Atoms of the same element that differ in amount of neutrons.

- Sum of protons and neutrons in nucleus is the mass number.

Chemical Compounds

• A substance formed by the chemical combination of two or more elements.

- Water: H2O, 2 molecules of hydrogen

1 molecule of oxygen

Chemical Bonds

• An ionic bond is formed when one or more electrons are transferred from one atom to another.

- An atom that loses electrons = positive

- An atom that gains electrons = negative

• Example: Table Salt, NaCl

Chemical Bonds

• A covalent bond forms when electrons are shared between atoms.

- Example: Water, H2O

Section 2.2

2.2-Water

• A water molecule, H2O, is neutral.

• It is polar.

• Water molecules are held together by hydrogen bonds.

Hydrogen bonds

• Cohesion is an attraction between molecules of the same substance.

• Adhesion is an attraction between molecules of different substances.

Solutions and Suspensions• A solution is an even mix of components.

- A solute is the substance that is dissolved (salt)

- A solvent is the substance in which the solute dissolves (water)

• A suspension is a mixture of water and non-dissolved material

Example- blood

pH scale

• Ranges from 0-14.

• Solutions with a pH below 7 are acidic.

• Solutions with a pH above 7 are basic.

Section 2.4

2.4-Chemical Reactions

• A process that changes one set of chemical reactions.

- Reactants: elements that enter into a reaction.

- Products: elements that are produced by a chemical reaction.

H2 + O H2O

Activation energy

• The energy to get a reaction started.

• It is a factor in whether the overall chemical reaction releases energy or absorbs energy.

Enzymes

• A catalyst is a substance that speeds up the rate of a chemical reaction.

• Enzymes are proteins that act as biological catalysts; speed up reactions in cells.