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

Copyright Pearson Prentice Hall

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.


Chemical Bonds

A covalent bond forms when electrons are shared between atoms.

8

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

Copyright Cmassengale


The Water Molecule

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


The Water Molecule

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


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)


The Water Molecule

Adhesion is an attraction between molecules of different substances.

Capillary Action


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



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



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.



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**

biology basic chemistry – chapter 2 section 1 and 2

Documents