CHEM 112 Chapter 1 notes
CHEM 112 Chapter 1 notes Chem 112
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This 5 page Class Notes was uploaded by Ale Guzman on Wednesday January 27, 2016. The Class Notes belongs to Chem 112 at University of Illinois at Chicago taught by Dr. Sherwin Montano in Winter 2016. Since its upload, it has received 108 views. For similar materials see General Chemistry in Chemistry at University of Illinois at Chicago.
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Date Created: 01/27/16
SPRING 2016 CHEM 112 MONTANO Chapter 1 Matter Properties of matter are determined by the properties of the molecules and/or atoms it is composed of o Ex. Water (H O) Hydrogen Peroxide (H O ) 2 2 2 Water is stable, drinkable, and if you boil it, it will just evaporate Hydrogen peroxide is not nearly as stable, NOT drinkable, and if you boil it, it might explode. These two molecules are one atom apart (one more oxygen is added to water to make hydrogen peroxide), but the properties of the molecules are completely different. Atoms & Molecules Atoms o Submicroscopic particles that constitute the fundamental building blocks of matter o Free standing atoms are usually rare in nature (but usually found in labs for experimental purposes), and they are usually combined with other atoms to make molecules Molecules o As said before, molecules are a combination of two or more atoms o Could be two of the same atoms, like O or2different atoms like H 2 Classification of Matter Solid o Atoms/molecules are packed, they don’t move o Fixed volume/rigid shape o Can be crystalline (definite shape, may be transparent like a crystal) or amorphous (lacking a physical form or shape) Liquid o Atoms/molecules are less packed together/can move around freely o Like water in a bottle, the water sticks together but if you move the bottle around, the water swishes around the bottom Gas o Atoms/molecules have a lot of space, can freely move around o Assumes shape of the container (unlike solids and liquids, gasses are able to take up the entire space of the container it is in) o Can be compressible (since there is so much space between the atoms/molecules) Within these states of matter, there are two different compositions: o Pure Subtances SPRING 2016 CHEM 112 MONTANO Element: one type of atom by it self ONE atom of oxygen Compound: a molecule, collection of two or more atoms bounded by a chemical bond A MOLECULE of oxygen, O 2 Water, H 2 o Mixtures Heterogeneous Mixture Not uniform in composition, you can tell there are different components to this mixture o Wet sand Homogenous Mixture Uniform throughout, but the molecules are not bonded chemically o Tea with sugar, the water in the tea has dissolved the sugar so it is the same throughout, however, the water, the tea, and the sugar are not bonded chemically so it is not a pure substance Separating Mixtures Homogenous mixtures can be separated by distillation o By boiling the mixture, the atom/molecule with the lowest boiling point will separate first, then followed by the next with the second lowest boiling point, and so forth Heterogeneous mixtures can be separated using filtration o If there is a insoluble solid in a liquid (like sand in water), filtering papers inside a funnel will trap the solid while the liquid seeps through the paper, thus separating them o A mixture like sulfur and iron (two solids) can be separated by using a magnet to catch the iron (since sulfur is not magnetic it will not be caught by the magnet) Chemical & Physical Physical changes o changes that alter appearance, but not composition o State changes are physical: if you boil water, it will turn into a gas, but it is still water Physical property o It is a property that a substance displays without changing the molecular composition Odor, taste, color, appearance, melting/boiling point, density Chemical changes o Things that alter the molecules chemical composition SPRING 2016 CHEM 112 MONTANO o When iron rusts, the Iron atoms turn into iron oxide, which is a completely different molecule Chemical properties o A property that a substance displays ONLY when it is in the process of changing its molecular composition Corrosiveness, acidity, flammability, toxicity Units of measurement The units of measurement most commonly used in science: o Meter (m) used for length o Gram (g) used for mass/weight o Liter (L) used for volume (liquid-based) o Second (s) used for time o Kelvin (K) used for temperature o Mole (mol) used for amount of substance (atoms and molecules) meters, grams, and liters have prefix multipliers to make it easier to specify how much of something you have o kilo- is 1000 m/g/L o milli- is 0.001 m/g/L Units of Kelvin can be derived from units Celsius and Celsius can be derived from Fahrenheit: o C = (F – 32)/1.8 o K = C + 273.15 Significant figures All certain numbers PLUS the first estimated number are significant. leading zeros (found in decimals) are not significant o i.e. : In the number 0.0045, the 0 in the ones place AND the two 0’s in the tenths and hundredths place (after the decimal point) are NOT significant. o This number (0.0045) has 2 significant figures. (4 & 5) trailing zeros WITH a decimal point are always significant. o i.e. : say you added an extra 0 to the end of the first example to make the number 0.00450. This number would have 3 significant figures INSTEAD of 2 because while the first three 0’s are not significant, the last 0 is because it is the estimated digit in this number (note in the first rule that estimated digits are significant). o Now say you added another 0, making the number 0.004500. This number will have 4 significant figures. (4, 5, and the 0 right after 5 are the certain numbers & the last 0 is the estimated digit) trailing zeros WITHOUT a decimal point are usually not significant. o While the number 0.004500 has 4 significant digits, the number SPRING 2016 CHEM 112 MONTANO 4500 only has 2. zeros in between non zero digits are significant. o The number 45001 has 5 significant figures. o The number 4050 has 3 significant figures. o The number 40.05 has 4 significant figures. o The number 40.050 has 5 significant figures. Significant figures in calculations Calculated numbers should not have more digits than measured numbers Do not include estimated numbers in calculations! Significant figures in multiplication & division: o round to the smallest amount of significant figures o i.e. : 1.4451 * 2.04 = 2.9684 ♒ 2.97 even though 2.9684 is the actual answer, 2.97 is the correct answer if we are using significant figures, since 2.04 has the smallest amount of significant figures (3). Significant figures in addition & subtraction: o look at the position after the decimal point and round to that position (use the number with the least amount of decimal places) o do NOT look at significant figures o 1.4451 + 2.0 = 3.4551 ♒ 2.5 2.0 is the limiting number in this case since it only shows up to the tenths place. Rules for Rounding if the last digit is GREATER THAN OR EQUAL TO 5, always round up. o 2.77 is rounded to 2.8 If the last digit is LESS THAN 5, always round down. o 2.73 is rounded to 2.7 Precision & Accuracy Accuracy: how closely the experimentally measured value agrees with the “right” known value o the values do not have to be close to one another as long as they average out to be the right value Precision: the experimentally measured values are very close to one another o The values do not have to be right to be precise o C = SPRING 2016 CHEM 112 MONTANO
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