1. Introduction to Chemistry
Chapter 3 – Biology I Honors

2. Matter Anything that has mass and takes up space
Matter has Two Major Types of Properties:
Physical Properties
Chemical Properties

3. Physical Properties of Matter
Properties that can be observed and measured without permanently changing the identity of the matter.
Examples:
Mass
Volume
Color
Texture
State/phase
Boiling and melting points

4. Types of changes in matter
Physical change
a change in which a substance is NOT permanently altered
ex. Ice to water example

5. Types of changes in matter
chemical change in matter
a process in which a substance is permanently altered. When a chemical change is complete, it is difficult (and perhaps impossible) to get the original substance back.
Example: frying and egg; burning wood

6. element
a pure substance that cannot be broken down into any simpler substances.
An element is matter that consists entirely of one type of atom.

7. periodic table of elements
109 different elements - 90 of these are found in nature

9. atom
the smallest piece of an element that still has all the characteristics of the element

10. atomic structure
nucleus of an atom - the center of the atom; composed of protons and neutrons
proton - subatomic particle that has mass and a positive charge
neutron - subatomic particle that has mass and has no charge

11. atomic structure
electron cloud - the region outside the nucleus where electrons may be found.
electron –
almost no mass
negative charge
Constant motion
outside nucleus

12. Related Terms atomic number - the number of protons an atom has.
atomic mass - the total number of neutrons and protons in an atom
Electrons are not considered because they have so little mass.

13. ion when an atom loses or gains electrons it becomes an ion.
Ions are atoms that have either a positive or negative charge.

14. Combinations of Elements
Mixtures, solutions, compounds, molecules…

15. mixture two or more substances that are physically combined
they still retain their own properties and can be separated using simple physical means.

16. solution solution - a mixture in a liquid form. solute solvent
Atoms/molecules are very evenly dispersed.
solute
the substance that gets dissolved in making a solution
solvent
the substance that does the dissolving in a solution.
Water is said to be the "universal solvent" because it dissolves lots of different things.

17. compound
a substance that consists of two or more different types of atoms that are chemically combined
that is, they cannot be easily separated,
the individual characteristics as elements no longer exist - they change completely.
The elements in a compound are combined in very definite proportions - unlike the substances in a mixture. THINK WATER!!!

18. molecule
the smallest part of a compound that still has the characteristics of the compound.

19. chemical bonds
the means by which different atoms are combined to make compounds.
bonds occur due to interactions between the electrons of different atoms.
Chemical bonds form as atoms "try" to achieve stability - this means having complete outer energy levels.

20. ionic bonds
a bond resulting from the total transfer of an electron from one atom to another.
Their resulting opposite electrical charges will hold them together.
This is a strong bond, but can be easily broken.
Animation link

21. covalent bond a chemical bond formed by the sharing of electrons.
By sharing electrons, each atom fills up its outer electron shell.
very strong bond
This is a and is found in most of the chemicals in living organisms.
Covalent bonds may be single, double or triple.

22. chemical reaction any process in which a chemical change occurs.
reactants - substances that enter into a chemical reaction
products - substances that result from a chemical reaction

23. WATER
Water = H20 = 2 hydrogen atoms covalently bound to an oxygen atom.

24. Water is unique and very important for life on Earth
Water has unique properties that make it essential for life. Life as we understand it could not exist without water.
75% of Earth's surface is covered with water.
Water is the most abundant compound in nearly all living things.

25. What is so unique about water??
It begins with Oxygen
Oxygen is electronegative.
This means that oxygen LOVES electrons and will NOT share them EQUALLY in a covalent bond.
In a water molecule, oxygen pulls the electrons of the two hydrogen atoms closer to itself.
As a result, the two ends of a water molecule are DIFFERENT.
One end (the oxygen end) has a slight negative charge
the other end (the hydrogen end) has a slight positive charge.
Because of this, water is said to be POLAR.
Polarity - when molecule has one end that is different from another.

26. Water’s Polarity

27. how polar substances interact
Polarity causes a water molecule to act like a "little magnet".
The negative end will be attracted to positive particles
The positive end will be attractive to negative particles.
The Polarity of water is the quality of water that causes all of its other important properties to exist.

28. hydrogen bonds
Water molecules are attracted to each other due to their polarity
Weak bonds are created between the oppositely charged regions of different water molecules.
These bond are called Hydrogen Bonds.
They are weak compared to covalent bonds, BUT
They are stronger than having no bonds at all.
It is because of these bonds between water molecules that water acts so uniquely and is so important to life.

29. hydrogen bonds

30. Properties of Water
All of waters unique properties are derived from its polarity.

31. Water is Cohesive Water tends to stick to itself Example:
Surface tension
Water striders
Helps in pulling water up plants from the roots

32. Water is adhesive Water tends to stick to other substances Examples
As long as they are also polar or charged
Examples
Capillary action
Water rises up very narrow tubes b/c it clings to the walls of the tube.
Also aids in pulling water up plants from roots

33. Water has a high specific heat
Means it takes a lot of energy to raise the temperature of water by 1 degree C.
Water can store lots of heat without changing it's temperature very much.
Why?
It takes lots of energy to break the hydrogen bonds and allow water molecules to move rapidly.
Causes our body temperature and temperature of earth to be more stable.

34. Water has a high heat of vaporization
Means it takes a lot of energy to change a gram of water from the liquid to the vapor (gas) state. Water is not easily evaporated.
Allows us to retain our oceans, etc – they don't evaporate away into space;
Good for evaporative cooling – when you sweat, water evaporates and takes lots of heat energy with it and thus cools you down.

35. Ice FLOATS Water is less dense as a solid than as a liquid
Ponds do not freeze solid – ice forms a layer that insulates/protects the water underneath from getting too cold.

36. Water is a GREAT solvent
As long as the solute is charged or polar.
“the universal solvent”
Think salt water

37. Water tends to "organize" non polar substances.
Water would rather cling to itself than any nonpolar substance – so it separates from nonpolar substances.
Cell membranes are able to form because of this property!

38. pH a measure of the acidity or basicity of a solution.
Acid - a solution with excess hydrogen ions
Base - a solution with excess hydroxide ions

39. pH
Water = H2O = HOH
HOH sometimes separates (dissociates) into H+ and OH- ions.
More H+ ions gives an acid.
More OH- ions gives a base.
Pure water always has the same number of H+ and OH-, hence its pH is NEUTRAL

40. pH scale
Neutral pH = 7
Acid pH = 0 to 7
Base pH = 7 to 14

41. What makes water become acidic or basic?
ADDING acid or base
What is an acid?
A substance that readily gives up H+ ions to water
What is a base?
A substance that gives up OH- ions to water

42. Remember, water is a great solvent…
It readily pulls apart ionic substances
Example:
HCl (hydrogen chloride) is readily pulled apart by water into H+ and Cl-
Thus there are excess H+ in solution
You get an acid

43. pH in living things
Organisms seek to maintain a NEUTRAL pH (example - human blood - pH around 7.5).
HOMEOSTASIS!
Living things attempt to keep internal conditions CONSTANT
Buffers are substances in living things that will absorb excess H+ ions or OH- ions as needed to maintain a neutral pH.