Chapter 6Part 2

Pages 145-151

Compounds and Bonding

• Page 145

• Compound- a substance that is composed of atoms of two or more different elements that are chemically combined

• Most elements in nature are found combined in the form of compounds

• How and why do atoms combine?• Combine when the resulting compound is

more stable than the individual atoms.• For many elements, an atom becomes more

stable when its outermost energy level is full- by sharing electrons with other atoms

Sharing electrons

Page 146

• Covalent bond- force that holds atoms together when they are sharing electrons

• Most compounds in organisms have covalent bonds.

Molecule• A group of atoms held

together by covalent bonds.• No overall charge• Example-molecule of water

Chemical formula

• Page 147• Use the chemical symbol for atoms• Subscripts represent the number of atoms

present• Example:

Ionic Bonds• An atom gains or loses electrons, it has an

electrical charge (charged particle) and will assume the name ION.

• atoms combine with each other by gaining or losing electrons in their outer energy levels- not sharing of electrons

• Example page 147- sodium chloride

Chemical Reactions• Page 147• Occur when bonds are formed or broken,

causing substances to recombine into different substances

• All of the chemical reactions that occur within an organism are referred to as that organism’s metabolism

• Consists of reactants and products

Chemical Equations• Reactants• Products• Number before each formula indicates the

number of molecules of each substance• Subscripts in a formula indicate the number of

atoms of each element in a molecule of the substance

• Equations must always balance

Mixtures• Page 148• A mixture is a combination of

substances in which the individual components retain their own properties• Example- mixing sand and sugar

crystals

Solutions•A mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent)

Acids and Bases Page 149

• Chemical reactions can occur ONLY when the conditions are right

• Variables may include (but not limited to):– Temperature– Energy availability– Solute concentration– pH

pH

•A measure of how acidic or basic a solution is

What is an acid?

• Any substance that forms hydrogen ions in water

• Reacts with most metals• Tastes sour• Frequently feels sticky

• Examples: grapefruit, oranges, lemon, tomato, milk

What is a base?

• Any substance that forms hydroxide ions in water

• Feels slippery• Tastes bitter

• Examples: egg, antacid, ammonia, cleaners

Acids and Bases• A scale with values ranging from 0 to 14 is

used to measure pH• 0-6 acidic• 7 neutral (pure water)• 8-14 basic

Acids and Bases Video 8 minutes

• http://www.youtube.com/watch?v=Xeuyc55LqiY

BIG PICTURE

• An acid is any substance that form hydrogen ions (H+) in water

• A base is any substance that forms hydroxide ions (OH-) in water

• Mini lab 6.1

LAB- Analysis Questions

• 1. What would happen to our bodies if blood pH was changed or altered?

• 2. The pH of stomach acid is 2, why is this both good but possibly destructive to our bodies?

• 3. What could happen to our local environment if a company pumped materials into the atmosphere which created a drastic pH change in the rain water?