Download General Chemistry Lecture Notes and more Lecture notes Biochemistry in PDF only on Docsity!
INTRODUCTION
Chemistry is the study of matter, its structure, composition, properties, and the changes it undergoes. Chemistry if often called the central science, because a basic knowledge of chemistry is essential for the study of biology, physics, geology, ecology and many other fields. Here are some of the Branches of Chemistry: A. Pure Chemistry Analytical Chemistry Biochemistry Electrochemistry Environmental Chemistry Inorganic Chemistry Nuclear Chemistry Organic Chemistry Physical Chemistry Thermochemistry B. Applied Chemistry Chemical and Molecular Toxicology Chemical Kinetics Chemical Thermodynamics Food Chemistry Forensic Chemistry Industrial Chemistry Iodochemistry Medicinal Chemistry Photochemistry Phytochemistry Polymer Chemistry Quantum Chemistry Stereochemistry Synthetic Chemistry The Significance of Chemistry may vary according to its application: Health and Medicine Energy and the Environment Materials and Technology Food and Agriculture Technology is the application of science concepts; it is always associated with these terms: PRODUCT - PROCESS - EQUIPMENT Figure 1. The Japanese Character for chemistry literally means “change study”.
Scientific Method
- A logical approach to the solution of scientific problem.
- A systematical way of solving a scientific problem that is needed to be proven.
- Generally have five (5) steps: Problem, Observation, Hypothesis, Experiment, and Data and Conclusion Hypothesis:
- A tentative explanation or idea about how things work.
- A hypothesis guides you in further work to get a better answer. Example: "The moon is made of cheese" (note: this is the kind of hypothesis my wife would come up with). How could we test this hypothesis?
- Construct a rocket to go to the moon and return with samples
- Make a cheese pizza substituting the moon samples for the cheese
- Ask people (e.g. graduate students. No, wait, they aren't real people…) to eat the pizza and see if they can tell any difference from pizza made with real cheeseTM (from Wisconsin)
- Most likely conclusion: Hey, this pizza tastes like dirt New hypothesis (altered to include additional information from above experiment): The moon is not made of cheese, but is made of dirt, sort of like the Earth Theory:
- A theory is an explanation of the general principles of certain phenomena with considerable facts to support it.
- A theory remains valid only if every new piece of information supports it.
- If a single piece of available information does not support a theory, then the theory (as proposed) is disproved. Fact:
- An indisputable truth. Law:
- A summary of a whole array of observations on a particular subject.
- It describes a natural phenomenon without attempting to explain it.
- Can often be expressed by simple mathematical expressions or relationships. Other Examples:
- It is a fact that on June 30, 1908 in Tunguska, Siberia, an explosion equivalent to about 15 million tons of TNT occurred.
- It is a theory that this explosion was due to a natural, extra-terrestrial phenomenon and not to an activity associated with man.
- One hypothesis is that a comet collided with the Earth (a competing hypothesis is that a small black hole collided with the Earth)
ACCURACY AND PRECISION
Accuracy is the measure of how close a measurement comes to the actual or true value of whatever is measured. Precision is the measure of how close a series of measurements are to one another. SIGNIFICANT FIGURES
- Non- zero is all significant
- Zero: - Leading (less than one, on the left/before the non-zero) all are not significant
- Captive (in between non-zero) all are significant
- Trailing (more than one, on the right/after the non-zero)
- w/ decimal point, all are significant
- w/o decimal point, all are not significant
- Exact values are all significant SCIENTIFIC NOTATION n X 10 m n - stands for base (1 < n > 10) m - stands for exponent SIGNIFICANT FIGURES IN MATHEMATICAL OPERATIONS Addition and Subtraction least number of decimal place Multiplication and Division lowest number of significant figure SCIENTIFIC NOTATION IN MATHEMATICAL OPERATIONS Addition and Subtraction same exponents; proceed to the operation for the integers Multiplication add exponents; proceed to the operation for the integers Division sub exponents; proceed to the operation for the integers FACTOR LABEL METHOD OR DIMENSION ANALYSIS
Given Quantity X Conversion Factor = Desired Unit
- Dimensional analysis is used in numerical calculations, and in converting units
- Dimensional analysis can help us identify whether an equation is set up correctly (i.e. the resulting units should be as expected)
- Units are treated similarly to the associated numerical values, i.e. if a variable in an equation is supposed to be squared, and then the associated dimensions are squared, etc.
COMMON METRIC-METRIC CONVERSION AND ENGLISH-METRIC CONVERSION
VOLUME
1 ml = 1 cm^3 1 L = 10^3 ml = 10-^3 m^3 = 0.03531 ft^3 = 61.02 in^3 = 1.057 qt = 0.264 gal 1 m^3 = 10^3 L = 35.31 ft^3 1 ft^3 = 0.02832 m^3 = 28.32 L = 7.477 gal 1 gal = 3.788 L = 231in^3 1 pt = 16 oz 1 qt = 2 pt 1 gal = 4 qt LENGTH 1 km = 10^3 m = 0.6214 mi 1 m = 10^2 cm = 3.281 ft = 39.37 in 1 cm = 0.3937 in 1 in = 2.540 cm 1 ft = 12 in = 30.48 cm 1 yd = 3 ft = 91.44 cm 1 mi = 1760 yd = 5280 ft = 1.609 km 1 Ǻ = 10-^10 m = 10-^8 cm = 10-^1 nm 1 nautical mile = 6080 ft 1 light year = 9.461 x 10^15 m
MASS
1 kg = 10^3 g = 0.0685 slug 1 kg = 2.205 lb when g = 9.80 m/s^2 1 g = 6.85 x 10-^5 slug 1 slug = 14.59 kg 1 u = 1.661 x 10-^27 kg 1 ton = 2000 lbs 1 lb = 16 oz 1 oz = 28.35 g TIME 1 min = 60 s 1 hr = 60 min = 3600 s 1 day = 24 hrs = 86,400 s 1 wk = 7 days 1 month = 4 wk 1 yr = 12 mo = 365.24 d= 3.156 x 10^7 s 1 leap year = 366 days 1 decade = 10 yrs 1 century = 100 yrs 1 millennium = 1000 yrs
TEMPERATURE
ºC = (ºF – 32) /1.
ºF = (1.8 ºC) + 32
K (kelvin) = ºC + 273. R (rankin) = ºF + 460
I. Pure Substance is a form of matter that has a definite or constant composition and distinct properties. a. Element is a substance that cannot be separated into simpler substances by chemical means. 3 categories of elements: b. Compound is a substance composed of atoms of two or more elements chemically united in fixed proportions. II. Mixture is a physical combination of two or more substances in which the substances retain their identity. a. Homogeneous mixture – the composition of the mixture is the same throughout the solution (have only one phase). Solution is a homogenous mixture of two or more substances. It has two components:
1. Solvent – the dissolving medium of a solution; present in larger amount 2. Solute – a substance dissolved in a solvent to form a solution; present in smaller amount Metal Non-metal Metalloid ➢Hard and dense ➢solid (except mercury) ➢lustrous ➢good conductor of heat and electricity ➢malleable and ductile ➢high melting point and high tensile strength ➢ some are gases, liquids and solids ➢ less dense ➢ low melting point and tensile strength ➢ poor conductor of heat and electricity (insulator) ➢ brittle and soft ➢ dull ➢has properties that fall between metal and non-metals Acid Base Salt ➢yields hydrogen ions (H+) when dissolved in water ➢has a pH of less than 7 ➢turns blue litmus paper to red ➢sour taste ➢electron-pair acceptor (Lewis acid) ➢proton donator (Brønsted acid) ➢yields hydroxide ions (OH-) when dissolved in water ➢has a pH of greater than 7 ➢turns red litmus paper to blue ➢bitter taste ➢generally feels soapy or slimy ➢electron-pair donator (Lewis base) ➢proton acceptor (Brønsted base) ➢ionic compound made up of a cation other than H+^ and an anion other than OH- (neutral) Types of Solution Solute Solvent Example
- Gaseous Solution Gas Gas Air
- Liquid Solution Gas Liquid Carbonated Drinks Liquid Liquid Vinegar Solid Liquid Brine
- Solid Solution Gas Solid H 2 in Pd metal
b. Heterogeneous mixture – characterized by the presence of two or more distinct phases, which have different properties. Suspension – heterogeneous mixture in which its individual components remain physically separated and can be seen as separate components. Colloids – heterogeneous mixture which exhibits Tyndall effect (scattering of light by particles in the colloid). PROPERTIES OF MATTER a. Physical Properties – properties that can be measured and observed without changing the composition or identity of a substance Color Brittleness Freezing point Magnetic property Odor Mass Melting point Malleability Density Volume Boiling point Ductility Texture Temperature Solubility Conductivity Hardness Specific heat Elasticity b. Chemical properties – properties that can be only be observed if the material undergoes a change that results to an alteration in its composition. Examples: Flammability, Corrosiveness , Combustibility, Oxidation or Reduction c. Extensive (Extrinsic) properties – properties that depends on how much matter is being considered. Examples: Mass, Length, Width, Height, Volume, Weight, Surface Area d. Intensive (Intrinsic) properties – properties that does not depend on how much matter is being considered. Examples: Boiling point, Melting point, Density, Hardness, Color, Taste CHANGES IN MATTER a. Physical Change – involves a change in phase, size and shape and other physical characteristics of matter but there is certainly no alteration in its composition. Liquid Solid Amalgam (Hg & Ag) Solid Solid Brass (Zn & Cu) Steel (C & Fe) Phase Change
“Mass cannot be created nor destroyed, the total mass remains the same.” During a physical or chemical change, the total mass of all substances before and the total mass of all substances after the change are the same. ENDOTHERMIC AND EXOTHERMIC PROCESS a. Endothermic process – any chemical process that involves heat absorption. b. Exothermic process – any chemical process that involves heat release.
UNIT 2: ATOMS
DEVELOPMENT OF ATOMIC STRUCTURE AND THEORIES
Chemists make their observations in the macroscopic world and seek to understand the fundamental properties of matter at the level of the microscopic world (i.e. molecules and atoms). The reason why certain chemicals react the way they do is a direct consequence of their atomic structure.
- Thales and Leucippus
- Democritus – a Greek philosopher who believed that there is an indivisible particle called “atomos”.
- John Dalton – proposed the "Atomic Theory" Dalton Atomic Theory states that:
- All matter is composed of very small particles called atoms.
- All atoms of an element are the same in properties and different from the atom of any other element.
- Atoms unite and lose its properties when combination occurs in chemical change to form compounds.
- The atom is not entirely altered in the formation of a compound, and its weight remains constant. Behavior of moving charge in magnetic field ✓ A charged particle moving though a magnetic field will feel a force perpendicular to the plane described by the velocity vector and magnetic field vector
2H 2 + O 2 → 2H 2 O
4g + 32g = 36g 36g = 36g
✓ This deflects the moving charged particle according to the " right hand rule " (based on a positive charge) ✓ A negative charge will be deflected in the opposite direction
- J. J. Thomson – proposed the “Plum Pudding" model ; the atom is composed of a positively charged material with the negatively charged electrons scattered through it. *Eugene Goldstein – discovered the positively charged particles called proton.
- Ernest Rutherford – proposed the “Nuclear Model” ; the atom is mostly empty space. There is a small, positive nucleus with the negative electrons scattered around the outside edge. *Sir James Chadwick – discovered the neutral-charged particles called neutron.
- Niels Bohr – proposed the Planetary Model : Electrons move in definite orbits around the nucleus, like planets moving around the nucleus. Bohr proposed that each electron moves in a specific energy level.
Atomic Number (Z) – equal to the number of protons in the nucleus of an atom; and also equal to the number of electrons in a neutral atom Atomic Mass or Mass Number (A ) – equal to the number of protons and neutrons in the nucleus of an atom Ions – a charged particle formed when neutral atom or group of atoms gain or lose one or more electrons Cation – a positively-charged particle; lose electrons (e.g. Mg+2) Anion – a negatively-charged particle; gain electrons (e.g. O-^2 ) Polyatomic ions – group of atoms that carry a charge (e.g. ClO 4 - ) Molecule – the smallest particles or units of a compound made up of atoms held together by special forces. Isotopes – atoms having the same atomic number but different mass numbers.
Allotrope – two or more forms of the same element that differ significantly in chemical and physical properties. For example, Graphite & Diamond Average Atomic Mass *note: %abundance should be in decimal EXAMPLE Mass No. Isotopic Mass % Abundance Ave. Atomic Mass Chlorine 35 34.969 u 75.53 % 37 36.966 u 24.47% 35.458 u Chlorine Average Atomic Mass = (34.969 X 0.7553) + (36.966 X 0.2447) = 35.458 u QUANTUM NUMBERS Orbital - space or region outside the nucleus where electrons are most probably located Energy Level- space or region where electrons stay or move (also referred to shell) Quantum Number - gives the probability of finding the electrons in an orbital of given energy. It also describes the distribution of electrons in hydrogen and other atom. FOUR QUANTUM NUMBERS Principal Quantum number (n) Azimuthal / Secondary Quantum number (ℓ) Magnetic Quantum number (mℓ) Electron-spin Quantum number (ms) Definitions also known as energy level or shells; refers to the average distance of the orbital from the nucleus n = 1, 2, 3… refers to the shape of the orbitals; ℓ = n – 1 s-orbital (0) spherical p-orbital (1) dumbbell d-orbital (2) lobe f-orbital (3) complex shapes refers to the 3D
- space orientation; ml = 2ℓ + 1 s = 1 p = 3 d = 5 f = 7 refers to the spin of two possible electrons in one orbital, opposite in direction ms = +½ or - ½ 1 0 0
Ave. AtomicMass=(isotopic mass 1 %abundance s-orbital ( sharp 1 ) ) +(isotopic mass 2 %abundance 2 )+ ...
2 20 Ca: Ar 4s
Ground-state Electron Configuration: Noble Gas Notation/ Abbreviated Electron Configuration: Electron Configuration for Ions Orbital Diagram Valence electrons (Electrons in the outermost energy level) Valence Orbital
20 Ca:1s 2s 2p 3s 3p 4s
Cation: Anion: Excited Electron Configuration Electronic Configuration and Quantum Numbers
UNIT 3: THE BASICS OF MODERN PERIODIC TABLE
DEVELOPMENT OF THE PERIODIC TABLE
- Johann Dobereiner – law of triads
- John Newlands – law of octaves
- Lothar Meyer – classification of the elements into table that accounted for the periodic variations in properties
- Dmitri Mendeleev – increasing atomic weight
- Henry Moseley – increasing atomic number CLASSIFICATION OF ELEMENTS
- Metals (everything on the left and middle region) ✓ Most metals are malleable (can be pounded into thin sheets; a sugar cube chunk of gold can be pounded into a thin sheet which will cover a football field), and ductile (can be drawn out into a thin wire). n ℓ mℓ ms ( 3, 1, 1, +½ ) 2 2 2 6 2 6 20 Ca : 1s 2s 2p 3s 3p
-1 2 2 6 2 6 19 Cl : 1s 2s 2p 3s 3p Isoelectronic promoted electron 2 2 6 2 3 1 16 S:1s 2s 2p 3s 3p 4s 2 2 6 2 5 19 Cl: 1s 2s 2p 3s 3p
- Metaloids (atoms in the boundary between the metals and metaloids: Boron (B), Silicon (Si), Germainium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), and Astatine (At)). These are some of the more useful materials for semi-conductors. ARRANGEMENTS OF ELEMENTS IN THE PERIODIC TABLE
- Period/Series – horizontal rows
- Family/Group – vertical columns
- Block – refers to valence orbitals of an element that are being filled PERIODIC PROPERTIES AND TRENDS Properties Trends Left to Right Top to Bottom Metallic Properties
- refers to the physical and chemical properties of metals Decrease Increase Atomic Radius
- refers to the radius or size of a neutral atom Ionic Radius
- refers to the radius or size of an atom when it carries a charge Cations are always smaller than neutral atom while anions are always larger than neutral atom. Ionization energy
- energy required to remove an electron Increase Decrease Electron Affinity
- energy change that occurs when an atom tend to gain an electron Electronegativity
- measure of the ability of an atom that is bonded to another atom to attract electrons to itself
UNIT 4: BASIC CONCEPTS OF CHEMICAL BONDING
Valence Electrons are the electrons in the highest occupied energy level of an element’s atom. It largely determines the chemical properties of an element. Lewis Electron Dot Formula – consists of chemical symbol of an element surrounded by a number of dots representing the number of valence electrons
Octet Rule – atoms are stable if their outermost shell is completely-filed with electrons (8 valence electrons). Exemption to the Octet Rule:
- Expanded Octet
- Less-octet
- Odd-number electron Chemical Bonds are the forces of attraction that holds together the atoms or ions when they combine to form a molecule or ion pairs in a given compound. TYPES OF CHEMICAL BOND Ionic Bond – a bond formed between oppositely charged ions by transfer of one or more electrons
