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CHEMISTRY

CHEMISTRY. It matters. Scientific Notation. Conventions: The coefficient “N”(number before the decimal) must be greater or equal to 1 and less than 10.  1<= N <10 If the exponent (e) is positive, move the decimal to the left (e) times.

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CHEMISTRY

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  1. CHEMISTRY It matters

  2. Scientific Notation • Conventions: • The coefficient “N”(number before the decimal) must be greater or equal to 1 and less than 10. •  1<= N <10 • If the exponent (e) is positive, move the decimal to the left (e) times. •  Given 6.022 X 10^23, move the decimal to the left 23 times • -If the exponent (e) is negative, move the decimal to the right (e) times • Given 7.63X 10^-5, move the decimal to the right 5 times

  3. Operations involving numbers in scientific notation Addition/Subtraction Make the exponents similar by moving the decimal point, add/subtract the coefficients and retain the exponent. Move the decimal and adjust the coefficient if necessary. Example: 8.52 X 10 ^16 + 9.7 X 10^15 85.2 X 10^15 + 9.7 X 10^15 = (85.2+9.7) X 10^15 85.2 X 10^15 + 9.7 X 10^15 = 94.9 X 10^15 85.2 X 10^15 + 9.7 X 10^15 = 9.5 X 10 ^16

  4. Operations involving numbers in scientific notation Multiplication Multiply the coefficients and then add the exponents. Move the decimal point and adjust the coefficient if necessary. Example: (1.74 X 10^5) X (2.89 X 10^6) (1.74 X 10^5) X (2.89 X 10^6)= (1.74 X 2.89) X 10^(6+5) (1.74 X 10^5) X (2.89 X 10^6)= 5.0286 X 10^11 (1.74 X 10^5) X (2.89 X 10^6) = 5.03 X 10^11

  5. Operations involving numbers in scientific notation Division Divide the coefficients and then subtract the exponents. Move the decimal point and adjust the coefficient if necessary. Example: (8.6 X 10^7) / (3.5 X 10^2) (8.6 X 10^7) / (3.5 X 10^2) = (8.6/3.5) X 10^(7-2) (8.6 X 10^7) / (3.5 X 10^2) = 2.45714286 X 10^5 (8.6 X 10^7) / (3.5 X 10^2) = 2.5 X 10^5

  6. Dimensional Analysis This is considered as a powerful method in understanding basic Chemistry and is an alternative to memorizing loads of formulas and techniques. The idea is to find a way to multiply, divide, or derive a quantity whose units is consistent with the unknown. Example: You don’t know how to solve for the density of an object but you know that its unit is ml/g. Because of its unit, you can try dividing the volume of the object by its mass.

  7. International System of Units (S.I. Units)

  8. States of Matter

  9. Properties of Matter Physical vs Chemical Physical: can be measured without changing the identity and composition of matter *temperature, color, length Chemical: can be measured only when composition of matter is changed; these properties measure the way substance may change or react with other substances *reactivity, combustibility

  10. Properties of Matter Intensive vs Extensive Intensive/Intrinsic: properties that depend on the quality and kind of matter but NOT on the amount of matter *amount-independent properties: temperature, density Extensive/Extrinsic: properties that change when the amount of matter is changed *amount-dependent properties: mass, volume, length

  11. Changes in Matter Physical: change in physical state/dimension of a substance, but not its composition *freezing water, cutting paper Chemical: change in the composition of a substance forming a new substance with different properties *spoilage of food, burning of wood, rusting of iron ** Law of Conservation of Mass: There is no detectable change in the mass of a substance during a chemical reaction

  12. Changes in Matter Nuclear: transformation of the nucleus of an atom resulting to a new atom -Nuclear Fission: splitting of a large/heavy nucleus -Nuclear Fusion: combination of two light nuclei -Radioactive decay: spontaneous breakdown of unstable atomic nuclei releasingalpha, beta, or gamma particles Note: In a chemical reaction, the composition of substances may be changed but the identity of individual atoms remain the same from reactant to products. The identity of individual atoms is changed; hence, new atoms are normally formed.

  13. Energy Changes in Matter Enthalpy/ Enthalpy Change (∆H) – heat content of matter * ∆H reaction or ∆H rxn = ∆H products - ∆H reactants * ∆H = ∆H final - ∆H initial Endothermic Reaction – energy is absorbed by the system, energy gain * +∆Hrxn, photosynthesis Exothermic reaction – energy is released by the system, energy loss * - ∆H rxn, combustion of fuel Activation Energy (Ea) – minimum amount of energy needed to convert reactants to products Catalyst – substance that speeds up a reaction

  14. Classification of Matter Matter Pure substance Mixture Element Homogenous Heterogeneous Compound Law of Definite Composition A pure compound always consists of the same elements that combine in the same proportions by mass Law of Multiple Proportions If elements A and B form more than one compound, the amounts of A that are combined in these compounds, with a fixed amount of B, stand in a small, whole number ratio.

  15. Classifications of Compounds Binary (2 elements) vs Ternary (3 elements) Organic (has carbon, except for CO2, CO3, and CO3-2) vs Inorganic (CO2, CO3, CO3-2 , and anything without carbon) Acids vs Bases vs Salt

  16. Acids, Bases, Salts Acids - proton (H+) donor - blue litmus paper to red - pH < 7 Bases -proton acceptors, produces hydroxide ion (OH-) - red litmus paper to blue -pH > 7 Salts -neutralized product of an acid and a base **Phenolphthalein = a liquid that is colorless but turns pink when it is mixed with a base/ basic solution

  17. Power of Hydrogen The pH determines the acidity/alkalinity of a compound pH = - log [H+] *[H+] = 1.00 x 10 ^-pH in aqueous systems *[H+] is the concentration (in Molarity or mol/L) of hydrogen ions pOH = - log [OH-] *[OH-] = 1.00 x 10 ^-pOH in aqueous systems *[OH-] is the concentration (in Molarity or mol/L) of hydroxide ions

  18. Mixtures Homogenous • One phase mixture • Also “solution”, mixture of two substances that is uniform all throughout • Colligative properties depend on the relative amount of solute and solvent in a solution. As the amount of solute in a solution increases, there is freezing point depression, boiling point elevation, and vapor pressure lowering. *air, vinegar, soy sauce, steel

  19. Mixtures Heterogeneous • Two or more phases • Suspension: relatively large particles *oil and water, sand in water • Colloid: small, insoluble particles, exhibits Tyndall effect • Tyndall effect: when light passes through the mixture, you can see its particles *milk, mayonnaise

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