1. Chapter 2 Lecture Outline See PowerPoint Image Slides
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2. Matter, Energy, and Life
Matter is anything that has mass and occupies space.
Energy is the ability to do work.
There are two types of energy:
Potential energy
Stored energy, available to do work
Kinetic energy
Energy of motion
Potential energy can be converted to kinetic energy to do work.

3. Law of Conservation of Energy
Energy is never created or destroyed.
The first law of thermodynamics
Energy can be converted from one form to another, but the total energy remains constant.
An object at the top of a hill has potential energy based on its location.
When the object rolls down the hill, the potential energy is converted to kinetic energy.

4. Forms of Energy There are five forms of energy: Mechanical energy
Energy of movement
Nuclear energy
Energy from reactions involving atomic nuclei
Electrical energy
Flow of charged particles
Radiant energy
Energy in heat, light, x-rays, and microwaves
Chemical energy
Energy in chemical bonds

5. What Is the Nature of Matter?
Atoms
The smallest units of matter that can exist separately
Elements
Chemical substances composed of the same kind of atoms
Listed on the periodic table
Each element is represented by a symbol of one or two letters.
The principal elements that comprise living things are:
C, H, O, P, K, I, N, S, Ca, Fe, and Mg.

6. The Periodic Table of the Elements

7. Atomic Structure Atoms are composed of: The atomic nucleus Electrons:
Protons - positively charged
Atomic number - the number of protons
All atoms of the same element have the same number of protons.
Neutrons – no charge
Electrons:
Orbit the nucleus in energy levels.
Are constantly in motion.

8. Atomic Structure

9. Elements
Atoms of the same element have equal numbers of electrons and protons.
Thus, they have a neutral charge.
Isotopes
Atoms of the same element that have different numbers of neutrons
Atomic weight - the average of all of the isotopes in a mixture
Mass number
The sum of protons and neutrons in the nucleus

10. Isotopes of Hydrogen

11. Electrons Electrons occupy specific energy levels around the nucleus.
Electrons closest to the nucleus have the lowest energy.
Energy levels hold specific numbers of electrons.
The first energy level can have up to 2 electrons.
All other energy levels can have up to 8 electrons.
Atoms seek to have a full outer energy level.
Atoms that have full outer energy levels are inert.
Other atoms seek to fill their outer energy levels through chemical bonds.

12. Electrons

13. The Formation of Molecules
Molecules consist of two or more atoms joined by a chemical bond.
A compound is a chemical substance made of two or more elements combined in chemical bonds.
The formula of a compound describes the nature and proportions of the elements that comprise the compound.
H2O

14. Molecules and Kinetic Energy
Molecules are constantly in motion.
Temperature is a measure of the average speed of the molecules in a substance.
The greater the speed, the higher the temperature.
Measured in Fahrenheit or Celsius
Heat is a measure of the total kinetic energy of molecules.
Measured in calories (amount of heat that will raise 1g of water 1 degree Celsius).
Heat and temperature are related.
Add heat energy to a substance and the molecules will speed up, and the temperature will rise.

15. Kinetic Energy, Physical Changes, and Phases of Matter
Three phases of matter:
Solid
Liquid
Gas
The phase in which a substance exists depends on its kinetic energy and the strength of its attractive forces.
Solids-strong attractive forces, low kinetic energy, little to no molecular movement
Liquid-enough kinetic energy to overcome the attractive forces; more molecular movement
Gas-high kinetic energy, little to no attractive forces; maximum movement

16. Chemical Changes—Forming New Kinds of Matter
Chemical reactions
Creating different chemical substances by forming and breaking chemical bonds
Remember: Atoms form chemical bonds to fill their outermost electron energy levels, achieving stability.
There are several types of chemical bonds.
We will discuss:
Ionic bonds
Covalent bonds

17. Ionic Bonds
Atoms can gain or lose electrons to achieve a full outermost energy level.
Atoms with charge are called ions.
When an atom gives away an electron, it ends up with more protons than electrons and gains a positive charge; cation.
When an atom accepts an electron, it ends up with more electrons than protons and gains a negative charge; anion.
This process is called ionization.
An ionic bond
The attraction between oppositely charged ions
Example: NaCl
Sodium (Na) has one electron in its outer energy level.
Chloride has seven electrons in its outer energy level.
Sodium donates an electron to chloride, each achieving stability.
The positively charged sodium is attracted to the negatively charged chloride.

18. Ion Formation

19. Covalent Bonds
Atoms can achieve full outermost energy levels by sharing electrons instead of exchanging them.
A covalent bond is formed by the sharing of electrons.
The atoms sharing electrons sit close enough together so that their outer energy levels overlap.
Single covalent bond- one pair of electrons is shared. H2
Double covalent bond- two pairs of electrons are shared.
ethylene
Triple covalent bond- three pairs of electrons are shared. N2

20. Covalent Bonds

21. Hydrogen Bonds
The positive hydrogen end of one polar molecule is attracted to the negative end of another polar molecule.
This attraction is a hydrogen bond.
Hydrogen bonds hold molecules together.
Since they do not hold atoms together, they are not considered true chemical bonds.
Hydrogen bonds are very important in biology.
They stabilize the structure of DNA and proteins.
Water molecules can “stick” together with hydrogen bonds.

22. Water: The Essence of Life
Water has special properties that make it an essential molecule for life.
H2O
Electrons are shared unequally by hydrogen and oxygen.
This is a polar covalent bond.
Oxygen has more protons than hydrogen.
The electrons spend more time around oxygen than around hydrogen.
The oxygen end of water is more negative.
The hydrogen end of water is more positive.

23. Hydrogen Bonds

24. Mixtures and Solutions
A mixture
Matter that contains two or more substances that are not in set proportions
A solution is a homogeneous mixture of ions or molecules of two or more substances.
Components are distributed equally throughout.
The process of making a solution is called dissolving.
The solvent is the substance present in the largest amount.
Frequently the solvent is a liquid.
The solutes are the substances present in smaller amounts.
Aqueous solutions are solids, liquids, or gases dissolved in water.

25. Mixtures vs. Pure Substances

26. Water and Life
The following properties of water make it essential for life:
High surface tension
Water molecules stick to each other via hydrogen bonds.
Capillary action moves water through streams, soil, animals, and plants.
High heat of vaporization
A lot of heat is required to break the hydrogen bonds holding water together.
Large bodies of water absorb a lot of heat.
Temperate climates
Evaporative cooling

27. Water and Life Unusual density properties The universal solvent
Ice is less dense than water, so ice floats.
Allows aquatic life to survive in cold climates.
The universal solvent
Water can form hydrogen bonds with any polar or ionic compound.
Therefore, many things can be dissolved in water.

28. Chemical Reactions A chemical change:
When the bonds of compounds are made or broken, new materials with new properties are produced.
Happens via chemical reactions.
In a chemical reaction the elements remain the same, but the compounds they form and their properties are different.

29. Chemical Reactions and Energy
Chemical reactions produce new compounds with less or more potential energy.
Energy is released when compounds are made with less potential energy.
Energy is used to make compounds with more potential energy.

30. Chemical Equations
A chemical equation is a method of describing what happens in a chemical reaction.
For example, photosynthesis is described by the following equation:
Energy + 6CO2 + 6H2O → C6H12O6 + 6H2O
Reactants-substances that are changed, usually on the left side of the equation
Products-new chemical substances formed, usually on the right side of the equation

31. Five Important Chemical Reactions in Biology
Oxidation–reduction
Dehydration synthesis
Hydrolysis
Phosphorylation
Acid–base reactions

32. Oxidation-Reduction Reactions
Reactions in which electrons (and their energy) are transferred from one atom to another.
Oxidation
An atom loses an electron.
Reduction
An atom gains an electron.
For oxidation to occur, reduction must also occur.
Example:
Respiration
Sugar is oxidized to form carbon dioxide and oxygen is reduced to form water.
Energy is released in the process.
C6H12O6 + 6O2 → 6H2O + 6CO2 + Energy
Sugar + oxygen → water + carbon dioxide + energy

33. Dehydration Synthesis Reaction
When two small molecules are joined to form a larger molecule,
A molecule of water is released.
Example:
Joining amino acids to form proteins
NH2CH2CO-OH + H-NH CH2CO-OH  NH2CH2CO-NH CH2CO-OH + H-OH
amino acid amino acid = protein water

34. Hydrolysis Reactions
When a larger molecule is broken down into smaller parts:
A water molecule is split
Opposite of a dehydration synthesis
Example:
Digesting proteins into amino acids.
NH2CH2CO-NH CH2CO-OH + H-OH  NH2CH2CO-OH + H-NH CH2CO-OH
Protein water = amino acid amino acid 2

35. Phosphorylation Reactions
When phosphate groups are added to other molecules,
Phosphate groups are clusters of oxygen and phosphate atoms.
Bonds between phosphate groups and other molecules contain high potential energy.
When these bonds are broken, the energy that is released can be used by the cell to do work.
Phosphorylation reactions are commonly used to transfer potential energy.
Q-P + Z  Q + Z-P

36. Acid-Base Reactions
Occurs when ions from an acid interact with ions from a base
This type of reaction allows harmful acids and bases to neutralize one another.
H+Cl Na+OH- → Na+Cl- + H+OH-
Hydrocloric + Sodium Sodium Water
acid hydroxide chloride

37. Acids, Bases, and Salts An acid A base
Ionic compounds that release hydrogen ions (H+) into a solution
Phosphoric acid, hydrochloric acid
A base
Compounds that release hydroxide ions (OH-) into a solution
Sodium hydroxide, ammonia
Because bases are negatively charged, they will react with a positively charged hydrogen in solution.
The strength of an acid or base is determined by how completely it will dissociate in water.
Strong acids release almost all of their hydrogen ions into water.
Strong bases release almost all of their hydroxide ions into water.

38. Some Common Acids, Bases, and Salts

39. Salts Neither acids nor bases
Usually formed when acids and bases react
The dissociated hydrogen ions and hydroxide ions join to form water.
The remaining ions form ionic bonds, creating a salt.
This is an example of neutralization:
H+Cl Na+OH- → Na+Cl- + H+OH-
Hydrocloric Sodium Sodium Water
acid hydroxide chloride

40. pH A measure of hydrogen ion concentration
Solutions with high hydrogen ion concentrations
Have low pH
Are acidic
Solutions with low hydrogen ion concentrations
Have a high pH
Are basic
There is a 10-fold difference in hydrogen ion concentration between solutions that differ by one pH unit.
A solution with pH 4 has ten times as many hydrogen ions as a solution with pH 5.

41. The pH Scale

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