Chapter 6.1
Biology

Bio NOTES: Intro to the Chemistry
Your life DEPENDS on chemistry!
1. When you inhale oxygen, your body uses it in chemical reactions!
2. When you eat food, your body breaks it down and uses it in chemical reactions!

 Chemistry is the study of matter.
 Matter is anything that has mass and takes up space.
 Atoms are the building blocks of matter.
Brain Pop -Atoms

 Billions of atoms could fit on the head of a pin!
 Atoms are made up of even smaller particles –
1.
2.
3.
Neutrons
Protons
Electrons

 Nucleus – the center of an atom
 Within this nucleus are protons and neutrons.
 Neutrons – particles that have no charge
 Protons – particles with a positive charge
 Electrons – negatively charged particles located outside the nucleus.
 Constantly move around the nucleus in energy levels

 An element is the name for a specific Atom
 It is a pure substance that cannot be
broken down into other substances by chemical or physical means.
 But Elements can be joined together to form compounds

All living things are made up of chemical compounds
• A compound is made of atoms of different elements bonded together, such as H
2
• These compounds are the building
O or CO
2 blocks of our body and the world around us.
• The bonds that can hold compounds together are ionic, covalent, and hydrogen bonds.

3 Types of Bonds:
1. Ionic bond – forms between oppositely charged ions
• Ion = atom that has lost or covalent bonds gained electrons ionic bond gained electron
Sodium ion
(Na + )
Chloride ion
(CI )
Oxygen atom (O)
Carbon atom (C)
Carbon dioxide
(CO
2
)
Oxygen atom (O)
2. Covalent bond – forms when atoms share a pair of electrons
_
+
H
O
3. Hydrogen bond – Type of covalent bond forms between slightly positive hydrogen atoms and slightly negative atoms. Think WATER
H
+

POSITIVE IONS:
*Formed when an atom loses an electron.
*Lose the negative electron = atom is more positive
NEGATIVE IONS:
*Formed when an atom gains an electron.
*Gain a negative electron = atom is more negative

 1. Molecule - a compound in which the atoms are held together by covalent bonds.
 2. Ionic compound – a substance formed by ionic bonds.

Water and Solutions
6.3 pgs. 161-163

 Covalent bonds hold a water molecule together.
 The electrons are pulled towards the bond.
 This leaves one side slightly more
positive than the other.
 This makes water….

Opposite charges on opposite sides of a molecule




Molecules that have an unequal distribution of charges are called polar molecules .
Polarity is the property of having two opposite poles.
The oxygen and hydrogen in water share electrons, oxygen is bigger and holds the electrons closer so oxygen becomes a little negative and hydrogen becomes a little positive.

 Attraction between the H on one molecule and an
electronegative atom on another molecule.
 Electronegative= negative charge

 It is because of Waters’ Polarity and Hydrogen
Bonding that water is able to do Extraordinary things!!

Extraordinary Properties of Water
 Water molecules cling to other
surfaces.
 Example: Capillary action, as in water moving up a plant stem

Extraordinary Properties of Water
 Water molecules stick together
 Water LOVES itself, therefore it clings to itself!
 - this creates Surface
Tension

Most substances gain density when frozen.
This allows for aquatic life to live under the ice in the extreme cold.

Why ice really does float:

 Liquid water has hydrogen bonds that are constantly being broken and reformed.
 Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances.

Extraordinary Properties of Water
Solvent = a substance in which another substance is dissolved in
Solute = a substance dissolved in a solvent
Solution = when a solvent and solute are combined

 Water is polar so it
dissolves all polar molecules (example salt, sugar)
 Water will not dissolve non-polar molecules (example
Oil, grease) polar = has slightly charged regions nonpolar = does not have charged regions

 Water is polar
 Water molecules are held together with hydrogen bonds
 Properties
 Adhesion
 Cohesion
 Less dense when frozen
 Good Solvent

Pg 164-165

The pH Scale
**Some compounds form acids or bases
Scientists use something called the pH scale to measure how acidic or basic a liquid is
The scale looks at the concentration of positively charged hydrogen ions (H+) in a solution vs. the amount of negatively charged hydroxide ions (OH-)
The scale goes from values 0 through 14.
Brain pop

• An acid releases a hydrogen ions when it dissolves in water.
- high H + concentration
- Low OH- concentration
- pH less than 7
 Taste sour
 Corrode metals

A base releases hydroxide ions
 Taste bitter, chalky
 Feel soapy, slippery

A B
Left to right

 If you have an ionic compound and you put it in water, it will break apart into two ions.
 If one of those ions is H+, the solution is acidic.
 If one of the ions is OH-, the solution is basic.
There are other ions that make acidic and basic solutions, but we won't be talking about them here.

ACID BASE

 Pure water contains small, but equal amounts of ions: H+ and OH-
 On the pH scale the number is 7