1. .
CHAPTER 2: CHEMISTRY

2. Composition of Matter 2-1

3. Matter EVERYTHING IS MADE OF MATTER
Matter: anything that occupies space and has mass
Mass: quantity of matter an object has
Mass is NOT the same as weight
Weight: the pull of gravity on an object

4. Elements
Pure substances that cannot be broken down chemically into simpler kinds of matter
About 100 elements
Only 30 crucial to living things
Almost 90% mass of all living things made from combinations of only 4 elements!
Oxygen (O)
Carbon (C)
Hydrogen (H)
Nitrogen (N)

5. What we are made of…..

6. Elements Each element has chemical symbols Consists of 1 or 2 letters
Most cases symbol derives from first letters in name of element
Some come from Latin words for elements
Example: Symbol for sodium = Na from word natrium (Latin)
Atomic Number
Atomic Mass
Element Symbol
Element Name

7. Atoms
Simplest particle of an element that has all the properties of that element
So small cannot be observed
Scientists therefore make models describing the structure/properties of atoms
Two main parts:
Nucleus
Electron shell

8. Nucleus Central core of atom Made up of two particles:
PROTONS NEUTRONS
Positively charged Neutral
+ 0

9. Electrons High-energy particles with little mass.
Move around nucleus at very high speed
Move within different energy levels
Electrons in outermost energy levels have the most energy
Each energy level can hold a certain number of electrons
First energy level holds 2
Second energy level holds 8

10. Electron orbits: Example Carbon

11. Compounds Pure substance made up of atoms of two or more elements
The amount of atoms in the compound are fixed
Example: Water, H2O indicates that atoms always combine in a proportion of two hydrogen atoms to one oxygen atom
Physical and chemical properties of a compound differ from the physical and chemical properties of individual elements that compose it

12. How do elements form compounds?
Most atoms are not stable as individual atoms
Depends on the number and arrangement of electrons in the atoms of elements
Atoms are stable when the outermost energy level is filled
Most atoms are not stable in their natural state  therefore tend to react with other atoms  in ways that make the atoms more stable (atoms react to make themselves more stable)
These reactions = chemical reactions

13. Chemical Reactions What does a chemical reaction consist of?
chemical bonds are broken
Atoms are rearranged
New chemical bonds—attachments—are formed

14. Chemical Vs. Physical Change
This is only a change in the state of the matter:
Solid  liquid; Solid gas
Gas solid; Gas liquid
Liquid solid; Liquid  gas
This is a change in the composition of matter

15. Why do atoms form bonds? TO BECOME MORE STABLE
Ionic Bonds
Forms when atoms gain or lose electrons
-Has 7e-
-Wants 8e-
-Has 3e-
-Wants 2e-
Why do atoms form bonds? TO BECOME MORE STABLE

16. Why do atoms form bonds? TO BECOME MORE STABLE
Covalent Bonds
Forms when two atoms share one or more electrons
-Hydrogen has 1e- in the outer electron shell
-oxygen has 6e- in the outer electron shell
-hydrogen wants 2e-
-oxygen wants 8e-
-they share to make each other happy
Why do atoms form bonds? TO BECOME MORE STABLE

17. Ionic or Covalent Bond? Metals Nonmetals Ionic: metal + nonmetal
Ex. NaCl
Covalent: nonmetal + nonmetal
Ex. HCl

19. Review Questions Define element, atom, compound, molecule.
How are particles arranged in the atom?
How can we predict which elements are stable under natural conditions and which elements tend to undergo chemical reactions?
How does an ionic bond differ from a covalent bond?
Neon seldom, if ever, combines with other elements to form compounds. Why is this so?
In the early 1900’s, hydrogen gas was used to inflate airships. After one large airship crashed and caught on fire, helium gas began to be used to inflate airships. Why was helium preferred over hydrogen?

20. Review Questions: Answers
Define element, atom, compound, molecule. Elements are substances that cannot be broken down chemically into simpler chemical substances. An atom is the simplest part of an element that retains all of the properties of the element. A compound is a pure substance made up of two or more elements. A molecule is the simplest part of a substance that retains all of the properties of the substance and that can exist in a free state.
How are particles arranged in the atom? Protons and neutrons make up the nucleus of the atom. Electrons move around the nucleus

21. Review Questions: Answers
How can we predict which elements are stable under natural conditions and which elements tend to undergo chemical reactions? Stable elements have filled outermost energy levels. Elements with unfilled outmost energy levels tend to be reactive
How does an ionic bond differ from a covalent bond? In an ionic bond, ions with opposite electrical charges attract each other. In a covalent bond, the atoms share pairs of electrons
Neon seldom, if ever, combines with other elements to form compounds. Why is this so? Neon has the maximum number of electrons that its outermost energy levels can hold. Thus, neon is stable and tends not to react with other atoms.
In the early 1900’s, hydrogen gas was used to inflate airships. After one large airship crashed and caught on fire, helium gas began to be used to inflate airships. Why was helium preferred over hydrogen? Hydrogen is very reactive, while helium is relatively unreactive.

22. ENERGY Ch. 2-2

23. Energy & Matter The ability to do work or cause change.
Energy cannot be destroyed or created
Energy can be converted into another form
Ex. Light bulb: electrical energy  radiant energy (light)  thermal energy (heat)

24. States of Matter
All atoms & molecules in any substance are in constant motion
Rate which atoms or molecules move determines the state it is in:
Solid
Liquid
Gas

25. States of Matter Solid Liquid Gas Definite shape Definite volume
Not compressible
Tightly packed particles
Liquid
Indefinite shape
Medium packed particles
Gas
Indefinite volume
Compressible
Loosely packed particles
Solid
Liquid
Gas

26. Chemical Reactions CO2 + H2O  H2CO3
Living things undergo thousands of chem. Rxns during lifetime
Consist of:
Reactants: left side of equation
Products: right side of equation
CO2 + H2O  H2CO3
REACTANTS
PRODUCTS

27. Energy Transfer 1. We take in food
2. Sugars undergo series of chemical rxns
3. Sugar & substances are broken down to carbon dioxide & water (cellular respiration)
4. During this process, energy is released for use by body
Exergonic Reactions: release of energy
Endergonic Reactions: absorption of energy

28. Activation Energy
In order for exergonic & endergonic reactions to begin, energy must be added to the reactants
The amount of energy needed to start a chemical reaction = activation energy
Catalysts reduce the amount of activation energy needed to begin a reaction
Enzymes: crucial catalyst for living things
We have thousands, each made for specific reactions

29. Activation Energy Diagram

30. Reduction-Oxidation Reactions
Many chemical rxns that help transfer energy in living things involve the transfer of electrons
These known as reduction-oxidation rxns OR
redox rxns
Oxidation rxns: reactant loses one or more electrons becoming more positively charged
Reduction rxns: reactants gain one or more electrons becoming more negatively charged
Always occur together
OILRIG: Oxidation Is Loss Reduction Is Gain (of electrons)

31. Example: Redox Reaction
Formation of NaCl: Sodium Chloride
Sodium atom loses electron to achieve stability when it forms ionic bond  sodium atom undergoes oxidation
When a chlorine atom gains an electron  undergoes reduction
Na + Cl  NaCl

32. Review Questions What are the three states of matter?
How can a substance be changed from a liquid to a gas?
State the difference between endergonic and exergonic reactions
Explain how a catalyst affects a reaction
Why does a reduction reaction always accompany an oxidation reaction
Living things need a constant supply of energy, even though many of the chemical reactions they undergo release energy. Why is this true?

33. Review Questions: Answers
What are the three states of matter? Matter can exist as a solid, liquid or gas
How can a substance be changed from a liquid to a gas? A substance can be changed from a liquid into a gas by heating
State the difference between endergonic and exergonic reactions: Endergonic reactions involve a net absorption of free energy. Exergonic reactions involve a net release of free energy.
Explain how a catalyst affects a reaction: A catalyst lowers the amount of activation energy that is required for a chemical reaction to begin.
Why does a reduction reaction always accompany an oxidation reaction? If an atom is oxidized (loses electrons), then another atom must be reduced (accept those electrons that have been lost).
Living things need a constant supply of energy, even though many of the chemical reactions they undergo release energy. Why is this true? Even exergonic reactions need a small amount of energy—activation energy—to begin.

34. SOLUTIONS Ch. 2-3

35. Describing Solutions
Mixture which one or more substances are uniformly distributed in another substance.
Solute: substance dissolved in the solution
Solvent: substance in which the solute is dissolved
EXAMPLE: sugar water
Sugar = solute
Water = solvent
Concentration of solution is measurement of the amount of solute dissolved in fixed amount of solution
The more solute dissolved, the greater the concentration of solution
Aqueous solutions: water is solvent
Crucial for living things

36. Mixture Two main kinds: Homogeneous: uniformly mixed throughout
Ex. Sugar water
Heterogeneous: not uniformly mixed throughout
Ex. Oil & vinegar salad dressing

37. Acids & Bases
One of the most important aspects of a living system is the degree of its acidity or alkalinity
Alkaline = Base

38. Acids
If the number of hydronium (H3O+) ions in solution is greater than the number of hydroxide (OH-) ions in solution = acid
Ex. of Acidic solutions: Orange juice, Vinegar
Ex. of common acid: hydrochloric acid (HCl)
How does it affect our everyday lives?
Sulfur dioxide (SO2): produced by burning fossil fuels, reacts with water in the atmosphere to produce acid rain
Acid rain: can make lakes too acidic to support life

39. Bases
If the number of hydroxide (OH-) ions in solution is greater than the number of hydronium (H3O+) ions in solution = basic
Ex. of common basic solutions:
Cleaning agents
Soaps
Ex. of common base: sodium hydroxide (NaOH)

40. Neutral
If the number of hydronium ions equals the number of hydroxide ions in solution
Example: Pure water
**Hydronium ion = H3O+
**Hydroxide ion = OH-

41. pH Scale
Scale for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution
pH of 0-7 = Acidic
pH of 0 is VERY acidic
pH of 8-14 = Basic
pH of 14 is VERY basic
pH of 7 = Neutral
pH of solution is measured with Litmus Paper

42. pH Scale
A solution with a pH of 3 compared to a solution with a pH of 5
pH of 3 is 100X more acidic than pH of 5
pH of 3 is 10X more acidic than pH of 4
pH of 1 is 1000X more acidic than pH of 4
pH of 13 is 10X more basic than pH of 12
**there is a 10X difference between each number in the pH scale

43. What does the pH scale look like?
BASE
ACID
NEUTRAL

44. Buffers
Chemical substances that neutralize small amounts of either an acid or base added to a solution
We have complex buffering systems keeping our body fluids at safe levels
Ex. Stomach acid & urine are acidic
Ex. Intestinal fluid & blood are basic

45. Review Questions What is a solution?
Describe the dissociation of water.
What pH value is neutral?
Define acid and base.
What is a buffer?
The active ingredient in aspirin is acetylsalicylic acid. Why would doctors recommend buffered aspirin for some people, especially those who have a “sensitive” stomach?

46. Review Questions: Answers
What is a solution? A solution is a mixture in which one or more substances are uniformly distributed in another substance
Describe the dissociation of water: The oxygen atom of one water molecule removes the hydrogen atom of another water molecule. This results in one hydronium ion (H3O+) and one hydroxide ion (OH-)
What pH value is neutral? A pH value of 7 is neutral.
Define acid and base: An acid is a solution that contains more hydronium ions than hydroxide ions. A base contains more hydroxide ions than hydronium ions.
What is a buffer? A buffer is a chemical substance that neutralizes small amounts of acids or bases added to a solution.
The active ingredient in aspirin is acetylsalicylic acid. Why would doctors recommend buffered aspirin for some people, especially those who have a “sensitive” stomach? The buffer reduces the acidity of the aspirin and thus is less irritating to the stomach.