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CHAPTER 1 & 2 CHEMISTRY IS EASY! Do you agree? Everything around you is chemistry - the desk you=re sitting at, the air you breathe, the food you eat. If you breathe and eat you have been doing chemistry. The two major classifications of everything we know is MATTER AND ENERGY. Matter is anything that occupies space and has mass (weight). Energy is the ability to change matter, either physically or chemically. Einstein gave an equation which showed a relationship between matter and energy : E = mc2 E stands for energy, m stands for mass and c stands for the speed of light. If we keep breaking down matter to its simplest stuff, we will finally get to atoms. How many kinds of atoms are there? The periodic chart lists them: approximately 90 naturally occurring atoms and the rest are man made radioactive atoms. ORGANIZATION OF MATTER ELEMENTS - Think of them as letters of the alphabet. The letter >a= can also be a word. Most of the time we put letters together and made words. The chemical symbols for the elements are given in the periodic chart. COMPOUNDS - Think of these as words. H2O is the formula for water. It has 2 hydrogen atoms and one oxygen atom. Every water molecule will have the same formula. There may be impurities in the water, but all water is H2O. Compounds are PURE SUBSTANCES, meaning that it has a fixed and definite composition. MIXTURES - Mixtures have several substances present and can vary from one sample to another. Salt dissolved in water can be a mixture. Two salt solutions can vary by the amount of salt dissolved in the water.
ENERGY Another definition of energy is the ability to do work. Energy can be divided into potential and kinetic energy. Potential energy is the energy by location or position. Kinetic energy is the stuff we see and feel that does the work. Some to the major kinds of energy are heat, electrical, light, radiant, mechanical, and chemical. Energy can affect matter. Too much heat energy can turn a steak into a clump of charcoal. Depending upon the substance heat is working on, the change can be either PHYSICAL or CHEMICAL CHANGES A physical change occurs without a change in composition. A chemical change changes the chemical composition. ICE, WATER, and STEAM are all made up of water H2O. The have the same formula but have different physical forms. This is the the stages of matter: solid, liquid, and gas. Ice is solid H2O. Water is liquid H2O. Steam is gas H2O.
Solid Liquid Gas
A solid has the atoms packed closely together. It has the least movement of the atoms. The liquid has more movement in its atoms and the gas has a great deal of movement. As you add heat to atoms, the atoms increase their movement. The more you heat them, the more they move. The gas has the greatest movement and the greatest volume. In this instance heat made a physical change on the substance. If you heated sugar enough to char it, you would get a chemical change. The product cannot be changed back to the original form. A physical change the substance has the same formula for the beginning and final product. With a chemical change the formula of the final product is different from the original product.
MEASUREMENTS AND THE METRIC SYSTEM A. Math Review
MEASUREMENTS A great deal of the research in chemistry depends upon measurement. We have little or no difficulty in dealing with measurement for every day occurrences. However, we tend to think of science measurement as different and difficult. We buy a pound of grapes, a gallon of milk or a yard of cloth effortlessly. Pounds, gallons and yards are the terms used in the English system. In scientific measurements the Metric system of kilograms, liters, and meters is used. There has been a push for American consumers to go to the metric system. We now have liter containers of drinks. The transition to the metric system is going very slowly simply because people are used to using the English system. Is the English system any better than the metric system? No! In fact the English system is much more difficult to use. Units of Length
Units of Volume
1 fluid ounce of water = 1 ounce of water * * For other liquids 1 fluid ounce is not the same as ounce, depending on the density of the liquid. This is covered in the section on density. Conversions 1 quart = 0.946 Liter (946 milliliters)
Units of Weight (Mass)
MILLI, MICRO, NANO, PICO - 3, 6, 9, 12 In chemistry we will be working with the metric system.
Deci = -1 1 dg = 1 x 10-1 g 1 x 101 dg = 1 g 1 x 103 mg 1 g Kilo = 103 = 1000 1000 g = 1 Kg 1 x 103 m = 1 Km Write the conversion equations for micrograms, nanograms, and picograms with grams.
HOW TO DO CONVERSION PROBLEMS - DIMENSIONAL ANALYSIS Relax! The Jackson approach to math is to use it as a tool to get at something else. It is not a philosophical approach. It is one of pigeon holes and formulas. Stuff >em in or plug >em in. In math generally you are given something and asked to find something else from what you were given. To set up a problem we divide it into two sections: WHAT YOU HAVE and WHAT YOU ARE LOOKING FOR Problem: How many milligrams are in 8.6 grams? A) Write what you have
B) Write what you are looking for
C) Scan your mind to see if you have anything relating to grams and milligrams. (Hint: milli, micro, nano, pico)
D) Write down the conversion factors for mg and g.
Which one are you going to pick? If you pick the first one, nothing cancels out on the left and you have g2/mg so g2/mg does not equal mg on the right. If you pick the second one, the grams cancel out and you have - mg = mg Problem: How many nanograms are present in 5.2 milligrams? A) 5.2 mg B) 5.2 mg = __________ng C) Mind scan 1 g 1 x 103 mg
1 g 1 x 109 ng MORE PROBLEMS Convert: 1) 35 mg to pg 2) 7.2 kg to mg 3) 86 pg to ug 4) 18 dl to mL 5) 32 mg to g 6) 63 mL to L 7) 13 kg to mg 8) 2.5 x 104 ug to pg 9) 62 L to mL 10) 5.7 x 10-2 uL to L 11) 6.7 x 10-4mg to g
12) The yellow light given off by a sodium lamp has a wavelength of 589 nm. Express than in a) Angstroms and b) meters. ( 1 x 1010 Angstroms = 1 meter)
13) The radius of a sodium atom (Na) is 1.23 Angstroms. Express that in meters.
14) A 5 mL sample of water has a mass of 5 grams. What is the mass of 1 liter of water?
15) Challenge! A speed limit is 40 km./hr. What is that in feet per second? (ft/sec) Temperature Fahrenheit: Water boils at 212oF. Water freezes at 32oF. Celsius: Water boils at 100oC. Water freezes at 0oC. (centigrade) Kelvin: Water boils at 373oK. Water freezes at 273oK. OoK is absolute zero - as cold as you can go. No molecular activity at OoK. Formulas: oK = oC + 273o 1.8C = Fo - 32 NOTE: Always do the math of the brackets first. Problems: 1. In the lab a reaction took place at -20oC. What was that on the Kelvin scale?
2. 200oK = ________________oC
3. 98.6oF = _______________oC
4. 54oC = _________________oF
Density D = M/V D = density (g/ml) Density is a relative term, meaning how "heavy" per unit size something is. Example: Two people weigh 185 pounds. One is "solid" a football player. His weight is in muscle. His volume is not all that big. Another is "sloppy" heavy. His weight is in a gut. His volume is greater.
Problems: 1. An object has a mass of 100 g and a volume of 50 cm3 (think of cm3 as ml). What is the density?
2. The density of an object is 4.0 g/ml and it weighs 1.00 kg. What is its volume? (convert kg to g first)
3. A steel ball has a density 7.2 g/cm3 and a volume of 5.0 liters. What is its weight? (Convert liters to mL first)
How can we measure volumes? In a graduated cylinder that has 50 ml water, we put a steel ball in, the water now goes up to 60 ml.
The volume of the steel ball is 10 ml.
Specific Gravity Def: The ratio of the density of a particular substance compared to water at 4oC. 1 g water has a volume of 1 cm3 (1 ml)
Specific gravity does not have units - it is a ratio. The density of water is 1 g/ml. The specific gravity of water is 1.
Problems: 1. An object has a density of 7.2 g/ml, determine its specific gravity.
Sp. gravity = Density of unknown Density of water2. The specific gravity of water is 1. What volume is occupied by 500 g? (Since sp. gravity H2O = 1, density = 1.0 g/ml) D = M/V 3. An object weighing 250 g has a volume of 200 ml. Calculate its specific gravity.
CALORIES A calorie is a unit of heat energy. One calorie is the amount of energy required to heat 1 gram of water 1oC. A kilocalorie is 1000 calories. A kilocalorie is represented by a capital >C=. The calorie people use when referring to food calories, it is a kilocalorie.
Specific heat is the amount of heat required to raise 1 gram of a substance 1E Celsius. This can be given for either calories or joules in charts.. Specific heat of water 1 cal/gEC The lower the value for specific heat, the easier for the substance to heat up. Insulators will have high specific heats. calories = (mass) (Δ temperature) (SpH) Δ means change SpH means specific heat temperature is given in Celsius
The specific heat of aluminum is 0.217 cal/gEC. Calculate the amount of heat in calories required to raise the temperature of 10 g of aluminum by 13EC.
How many calories does it take to heat 50 grams of water from 32EC to 50EC?
HEAT OF FUSION It takes energy for matter to changes phases. For a solid to change to a liquid, it takes heat energy, either referred to as calories or joules. These values are given in charts. calories = (mass) (ΔHfus)
Heat of fusion for water ΔHfus = 80 cal/g HEAT OF VAPORIZATION To go from the liquid to the gas phase, it requires energy. This is referred to as the heat of vaporation. calories = (mass) (Δ Hvap) Heat of vaporation of water ΔHvap = 540 cal/g Given: Specific heat of ice = 0.5 cal/gE Specific heat of water = 1.0 cal/gE ΔHfus H2O = 80 cal/gE ΔHvap H2O = 540 cal/gE How many calories are required for 5.0 grams of ice at -5EC to go to steam at 100EC? 1) -5EC ice to 0EC ice 2) 0E C ice to 0E C water 3) 0EC water to 100EC water 4) 100EC water to 100EC steam | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Thursday, January 03, 2008 09:48:35 AM |