University:
Emory University
Course:
CHEM 141 | General Chemistry I
Academic year:

2021
Views:

162

Pages:

3
Author:

Aiden F.

Intro to Chem Lecture: 01.28.21 Chemistry is the branch of science that deals with the nature of matter and energy Macroscopic chemistry world: Objects we can see/touch/deal with daily Microscopic chemistry world: involves atoms and molecules Scientific Methods: - Observations are made and information is collected Hypothesis Formulated to provide a tentative explanation of the facts Law: A large amount of data related to a certain phenomenon have been collected Theory: A unifying principle that explains a large body of facts • Combustion The word "chemistry" can be applied to a wide variety of ideas: Rusting Absorption /Emission of energy Phase changes Formation of Atoms/Molecules Nuclear Reactors Chemistry is the study of change. The principles of Chemistry are used to: Describe WHAT Changed Describe WHAT happened to cause this change Describe WHY the sample has exhibited a specific change A number without a unit is meaningless → 200 (200 what?) To avoid confusion scientists have agreed on a standard set of units → SI Scientists use SI or the closely related metric units Important Measurements we'll use the most 1 kilogram (1 kg) = 1,000 gram (1 g) = 1000 g 1 centigram (1 cg) = 0.01 gram 1 milligram (1 mg) = 0.001 gram = 0.001 g 1 microgram (1 ug) = 0.000001 gram = 0.000001 g Mass: How much stuff is there Weight: Gravitational pull Volume: Space Three Phases of Matter: Solid, Liquid, Gas Scientific Notation: Is a convenient way to write a very small or a very large number. → Example: 215 is written in scientific notation as: 215 = 2.15 x 100 = 2.15 x (10 x 10) = 2.15 x 10^2 → Example: 215. = 2.15 x 10^2 Decimal point is moved two places to the left, so exponent is 2. 0.002 15 = 2.15 x 1/1000 = 2.15 x 1/(10 x 10 x 10) = 2.15 x 1/10^3 = 2.15 x 10^-3 Temperature Conversion: F = (C * 1.8) + 32 C = (F - 32) / 1.8 50 C in F: F = (1.8 * 50) + 32 = 132 Density relates the mass of an object to its volume. Density is usually expressed as: D = m / v (mass / volume) g/mL or g/cm^3 Units: grams per cubic centimeter (g/cm^3) for solids grams per milliliter (g/mL) for liquids Problems (Sig Figs) Sig Fig Rules 1, 2 42.423 -> 5 sig fig 39872347 -> 7 sig fig 911 -> 3 sig fig Sig Fig Rules 3, 4, 5 8000 -> 1 sig fig 40004 -> 5 sig fig 30300 -> 5 sig fig -> 4 sig fig 8000 apples -> 4 sig fig 85 x 10^100 -> 2 sig fig 85 x 10^0 -> 2 sig fig 14.00 -> 4 sig fig