CHEMISTRY of LIFE Chapter 2

The Nature of Matter

Important Terms Atom: basic unit of matter Fun Fact – 100 million atoms make can fit across your pinkie nail! Subatomic Particles: make up an atom Protons – p+ Positively charged particles Neutrons – n0 neutral particles Electrons – e- negatively charged particles n0 and p+ are found in the nucleus of the atom e- are found orbiting the nucleus

Diagram of an Atom Yellow = protons Orange = neutrons Grey = electrons

More Important Terms Element: a pure substance that consists entirely of one type of atom All elements are found on the periodic table Elements are represented by symbols Ca H Ar I Mg K Compound: a substance formed by the chemical combination of 2 or more different elements in definite proportions. Represented by formulas H2O C6H12O6 CO2

Counting Atoms Formulas tell us how many of each atom there is in the compound H2O How many hydrogens? 2 How many oxygens? 1 C6H12O6 How many carbons? Hydrogen? Oxygen? 6, 12, 6

One More Important Term Molecule: smallest unit of a compound H2O  only 1 molecule of water 2 H2O  2 molecules of water CO2  1 molecule of carbon dioxide 5 CO2  5 molecules of carbon dioxide Let’s count the atoms again. 5 H2O How many hydrogen? 1 molecule has 2 H but there are 5 molecules 2 x 5 = 10 How many oxygen? 1 x 5 = 5 3 C6H12O6 C = 18, H = 36, O = 18

The Periodic Table

C 6 Let’s Look at Carbon! Carbon 12.0107 Atomic Number Symbol Find Carbon on your periodic table! 6 Atomic Number C Symbol Carbon Element Name 12.0107 Atomic Mass

What Does the Periodic Table Tell Us? Atomic # = # of p+ (You must know this!) Atomic # never changes! Atomic Mass tells us the mass of each element. The protons and neutrons make up the mass! Mass # = the atomic mass rounded off Atomic mass of Carbon is 12.0107 so the mass # is 12.

How do we figure out n0 and e-? p+ = e- unless its an ion! Ion: a positively or negatively charged atom Cl- Na+ Al+3 S-2 Mass # = p+ + n0 In other words: mass # - p+ = n0 You must know these equations!!!!

Let’s Practice! Ex 1: Carbon Ex 2: Aluminum Atomic # = Atomic Mass = 6 13 12.0107 26.981538 12 27 6 13 12-6 = 6 27-13 =14 6 13

Let’s Practice! Ex 3: Gold Ex 4: Barium Atomic # = Atomic Mass = n0 = e- = Ex 4: Barium Atomic # = Atomic Mass = Mass # = p+ = n0 = e- = 79 56 196.96655 137.327 197 137 79 56 197-79 = 118 137-56 = 81 79 56

Chemical Bonds Ionic Bonds Covalent Bonds Hydrogen Bonds

Bonding When looking at bonding between atoms, we are concerned about the number of e- found in the outer orbit of each atom. We can tell how many e- are in the outer orbit by looking at where the element is located on the periodic table.

1e- in outer shell 8e- (except He – only 2 e) 2e- 3e- 4e- 5e- 6e- 7e-

Lewis Dot Diagrams When drawing out bonds between atoms, we use Lewis Dot Diagrams. LDDs show the # of e- in the outer orbit by using the symbol surrounded by dots. Examples: Sodium is found in the 1st column so it has only 1 e- in outer shell  Chlorine is found in the 7th column so it has 7 e- in its outer orbit  Na Cl

Now you practice! Al N Ar

Covalent Bonds Covalent Bonds occur when e- are shared between 2 atoms. Goal: to make all atoms “happy” All atoms want 8 e- in outer shell One exception = H only wants 2 You can have single (2 e-), double (4 e-), and triple (6 e-) bonds. Again we will use Lewis Dot Diagrams!

Let’s Draw Covalent Bonds Ex: F2 Ex: H2 F F H H

Let’s Draw Covalent Bonds Ex: N2 Ex: O2 N N O O

Let’s Draw Covalent Bonds Ex: H2O Ex: NH3 H O H H N H H

Ionic Bonds Ionic bonds occur when e- are transferred from one atom to another Ions: charged atom due to a loss or gain of e- Loss of e- results in a positive charge… why? Gain of e- results in a negative charge… why? Goal: to make all atoms “happy” All atoms want 8 e- in outer shell One exception = H only wants 2 Without a full outer shell, an atom is very “unhappy” or unstable.

Ionic Bonds Na Cl Ex: NaCl (Sodium Chloride) In order for both Na and Cl to be “happy” Na will give its 1 e- to Cl. How does that make Na “happy”? Na loses an e- and becomes Na+ Cl gains an e- and becomes Cl- Na Cl

Let’s Practice Ionic Bonds! Ex 1: Cl- Atomic # = Atomic Mass = Mass # = p+ = n0 = e- = Ex 2: Na+ Atomic # = Atomic Mass = Mass # = p+ = n0 = e- = 17 11 35.4527 22.989770 35 23 17 11 35-17=18 23-11 =12 17+1=18 11-1=10

Now you try! Ex 3: Al+3 Ex 4: S-2 Atomic # = Atomic Mass = Mass # = p+ = n0 = e- = Ex 4: S-2 Atomic # = Atomic Mass = Mass # = p+ = n0 = e- = 13 16 26.981538 32.066 27 32 13 16 27-13=14 32-16=16 13-3=10 16+2=18

Properties of Water

Polarity Polarity: the unequal distribution/sharing of e- Some atoms have a stronger “pull” and therefore hog the e- Causes an angular shaped molecule

Hydrogen Bonding Due to the partial (+) and (-) charges of H20 molecules, there is an attraction between H20 molecules (+) hydrogens are attracted to (-) oxygens of other molecules This causes H-bonds between H and O of different H20 molecules

Hydrogen Bonds

Cohesion Cohesion: attraction of molecules of the same substance Cohesion causes surface tension Allows water to form beads Allows bugs to “walk” on water

Adhesion Adhesion: attraction of molecules between different substances Attraction between water and glass forms a meniscus Allows for capillary action in plants – water can move from the roots all the way to the top of the plant

Solutions and Suspensions Mixtures are composed of 2 or more elements or compounds that are physically combined (not chemically combined) Salt and pepper, water and oil, sugar and sand Solution: even distribution of all components in the mixture (salt water, sugar water) Solute – the substance being dissolved Solvent – the substance doing the dissolving Suspension: mixture of nondissolved material in water (oil and water)

Solution

Suspensions

Acids, Bases, and pH

Let’s Start with Water H2O H+ + OH- Water is neutral because H+ = OH- H+ is a hydrogen ion OH- is a hydroxide ion Water is neutral because H+ = OH- When the H+ and OH- are unequal, the result is an acid or a base.

The pH Scale (power of hydrogen) pH scale indicates the concentration of H+ in a solution. Ranges from 0-14 7 = neutral = pure water H+ = OH- Below 7 = Acid H+ > OH- Above 7 = Base H+ < OH- The lower the pH the greater the acidity. The higher the pH the greater the basicness.

Neutralization Reactions We can mix an acid and base together in specific proportions to theoretically make water. When an acid (more H+) is added to base (more OH-), eventually the H+ will balance out the OH-, which makes the substance neutral.

Chemical Reactions

Chemical Reactions (Chem. Rxn) Chem rxn: a process that changes one set of chemicals into another Reactants: compounds that enter into a rxn Products: compounds that are a result of a rxn Chem rxn involve changes in bonds CO2 + H2O  H2CO3 6 CO2 + 6 H2O  C6H12O6 + 6 O2

Energy in Rxns Energy is stored in bonds. Rxns that release energy occur spontaneously. Energy is released when the bond is broken. Rxns that absorb energy will only occur with a source of energy Activation energy: energy required to start a rxn

Catalysts and Enzymes Catalyst: a substance that speeds up the rate of a chem rxn Lowers activation energy Enzyme: protein that acts as a biological catalyst Speeds up rxns in cells Enzymes are very specific to the process it has to speed up.

Organic Molecules Carbohydrates Lipids Proteins Nucleic Acids

Carbohydrates Sugar Elements: Carbon, hydrogen, oxygen Monomers: Monosaccharides Glucose, fructose, lactose 2:1 ratio of Hydrogen:Oxygen Job: Main source of energy for all living things (from the break down of sugars)

Glucose

Lipids Fats and Oils Elements: carbon, hydrogen, oxygen Monomers: 1 glycerol, 3 fatty acids H:O ratio is much greater than 2:1 Jobs: Long term energy storage Make up cell membranes Waterproof covering on leaves

Proteins Elements: carbon, hydrogen, oxygen, nitrogen Monomers: Amino Acids (there are 20) Functional Groups: Amino group = NH2 Carboxyl group = COOH “R” group Jobs: Speeds up chemical reactions Pumps molecules in and out of the cell Cell movement (cilia and flagella)

Alanine Serine

Nucleic Acids DNA and RNA Elements: Carbon, Hydrogen, Oxygen, Nitrogen, and phosphorus Monomers: Nucleotides Adenine, Thymine, Cytosine, Guanine, Uracil Functional groups: Phosphate group Nitrogenous base 5 carbon sugar (either deoxyribose or ribose) Job: Carries genetic information