Biology Basic Chemistry – Chapter 2 Section 1 and 2

BiologyBasic Chemistry – Chapter 2 Section 1 and 2

Matter and Atomic Structure Atom: the smallest

particle of an element; consists of: Protons p+: in the

nucleus Neutrons no: in the

nucleus Electrons e-: surrounds

the nucleus; equal to the number of protons

Matter and Atomic Structure Matter: anything that has volume and mass Element: a substance not broken down into simpler

substances by physical or chemical means Each element has a 1 or 2-letter symbol

Examples: oxygen (O), sodium (Na)

Molecule: A molecule is formed when two or more atoms join together chemically, may or may not be the same atom. Ex: hydrogen (H2) and water (H20)

Compound: a molecule composed of atoms of 2+ different elements that are chemically combined Ex: NaCl: salt, H2O: water

Matter and Atomic Structure Atomic Number: the number of protons in an

atom’s nucleus Mass Number: the number of protons and neutrons

in an atom Energy levels: the area of an atom surrounding the

nucleus where electrons are found

# of protons always equals the # of electrons; atoms have NO CHARGE

Energy Levels First energy level:

holds up to 2 electrons Second energy level:

holds up to 8 electrons

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Chemical Bonds: Two types (Ionic & Covalent)

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

These positively and negatively charged atoms are known as ions.

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Chemical Bonds

A covalent bond forms when electrons are shared between atoms.

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Water – A Molecule About 60-90 percent of an

organism is water

Water is used in most reactions in the bodyWater is called the universal solvent

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The Water Molecule

A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.

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The Water Molecule

Hydrogen Bonds (Weak Bonds)Because of their partial positive and negative charges, polar molecules can attract each other. – Polar Covalent

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The Water Molecule

Cohesion is an attraction between molecules of the same substance.Because of hydrogen bonding, water is extremely cohesive.Example: surface tension (bugs walking on water)

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The Water Molecule

Adhesion is an attraction between molecules of different substances.

Capillary Action

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Suspensions and Solutions

A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined.

Two types of mixtures can be made with water

SuspensionsSolutions

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Suspensions and Solutions

Suspensions Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out easily.

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Suspensions and Solutions

Solutions

All the components of a solution are evenly distributed throughout the solution.

solute—the substance that is dissolved.

solvent—the substance in which the solute dissolves.

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Suspensions and Solutions

When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules.

Na+

Na+

Cl -

Cl -

WaterWater

Acids & Bases (Form in Solution) Acid: any compound that forms H+ ions in

solution Base: any compound that forms OH- in

solution Water can dissociate to form acids and bases

H20 H+ + OH-

pH Scale A measurement system indicating

concentration of H+ or OH- ions in a solution Ranges from 0-14

0-6.99 = acidic solution 0 more acidic than 6.99 7.1-14 = basic solution (alkaline) 14 more basic than 7.1

http://pearl.maine.edu/windows/community/Water_Ed/pH/pH_whatisit_clip_image001.gif

**This scale can be presented 0-14 OR 14-0**