Conversions, Density, Sig Figs

1. Why study chemistry? 
1. Energy, find alternative fuels, improve efficiency, save environment, understand climate change
2. Medicine, improve scanning methods
3. Food safety, food additives, food coloring, preserves
4. Soap, perfume, cleaners, 
5. computer chips
6. Scientific Method used to understand things around us, to improve things, to question things
1. Question something
2. Devise and carry out experiments
3. Observations
4. Make a hypothesis (repeats back to step one)
5. Finally explain what is currently believed in a theory
2. Elements (about 118 right now known) 
1. An element is a substance made of only one type of atom.
2. About 24 elements are not natural - people made them in particle accelerators
3. You will need to learn the following elements symbols and their names: (Important) H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Kr, Sr, Ag, Sn, I, Ba, Au, Hg, Pb and U (look at the inside cover of your text)  
3. Periodic Table  An interactive table
1. You should know where to find the following on the Periodic Table
1. Alkali Metals (1A) Go to Activities, click on sodium and potassium in water.  Shiny, soft, super reactive solid metals. Can't find in nature - they've already all reacted.  Found often in salts:  NaCl
2. Alkaline Earth Metals (2A) Shiny reactive solid metals. Can't find in nature - they've already all reacted.  Found often in salts:  CaCl₂
3. Transition Metals - Medium soft to really hard solid metals except for mercury that is liquid. Fairly reactive to hardly reactive. Used in construction, coins, jewelry.
4. Lanthanides
5. Actinides
6. Noble Gases (8A) - All non-metal gases. (shocking I know ) Non reactive, don't make compounds naturally, stable.
7. Halogens (7A) - Fluorine and Chlorine are gases, bromine is a liquid, and iodine is a solid. All non-metals.
8. Chalcogens (6A) - Oxygen is a non-metal gas, S and Se are non-metals solids, Te is a solid metalloid, Po is a solid metal.
9. N Column (5A)
10. C Column (4A)
11. B Column (3A)
12. Metals - shiny, silver, malleable (can pound it flat), ductile (can make wires), conductors
13. Metalloids - solids, silver, brittle, semiconductors, all solids except Hg
14. Non-metals - insulators, brittle, different colors, 11 gases, 1 liquid, 5 solids
15. Hydrogen is really its own group.  It is unique.  It is a nonmetallic gas. 
16. Go to Activities, click on Interactive periodic table
17. Go to Activities, click on Periodic Table Groups
18. Groups are columns and have similar (not the same) chemical properties, Periods are rows
19. GAME: I can point at an element on the Periodic Table and you should be able to tell me:(Important)
1. Solid, liquid or gas
2. name if on the list above
3. group name
4. metal, metalloid or non-metal
20. 
4. Properties
1. Intensive - DOES NOT depend on size:  temperature, color, density, melting point (mp), boiling point (bp), hardness
2. Extensive - DOES depend on size:  mass, volume, heat, length, width, height, surface area
3. Physical - color, taste, smell, mp, bp, soft, hard
4. Chemical - flammable, rusts easily, corrosive, explosive, stable, non reactive, reactive
5. States of Matter
1. Solid - atoms in pattern but they still move a little (vibrate) 
2. Liquid - atoms touching and rolling around each other
3. Gas - atoms far apart, collide into each other and bounce apart
6. Changes:  Chemical vs Physical
1. Physical - just changing state (solid, liquid, gas) Freezing, boiling, melting, evaporating, dissolving, subliming, depositing.  There is not molecular level change, the substance is the same.
2. Chemical - rusting, fire, digestion , photosynthesis, battery reaction, getting high. There IS a molecular level change, the substance is not longer the same. 
5. Measurement
1. SI Units (systeme internationale) - basically the metric system which everyone but the US uses
1. mass - kilogram (kg)
2. length - meter (m)
3. temperature - Kelvin (K)
4. time - second (s)
2. Metric Prefixes (Important)- used to make base units bigger or smaller, always differ by multiples of ten (which is great because in the English system this sucks, I mean how many teaspoons are in a gallon?  how many inches in a mile?  how many ounces in a ton?)
1. Base units we'll use in this class: 
1. meter for length (m) ~ 39 inches or 1 yard 3 inches
2. liter for volume (L) ~ three 12 oz cans, 1/2 of a 2 liter bottle
3. gram for mass (g) ~ paperclip (funny how American drug dealers use the metric system)
2. Bigger than base unit
1. Giga (billion times bigger), 1Gm = 10⁹ m,   ratios used in calculations are (Gm / 10⁹ m)  or (10⁹ m / Gm) depending on what is canceling out
2. Mega (million times bigger), 1 Mm = 10⁶ m
3. Kilo (thousand times bigger), 1 km = 1000 m
4. For fun what is bigger than Giga???  Yep, it's Tera (trillion times bigger) like Terabyte
3. Smaller than base unit
1. centi (hundred times smaller), 100 cm = 1 m, ratios are (1 m / 100 cm)  or  (100 cm / 1 m)
2. milli (thousand times smaller), 1000 mm = 1 m
3. micro (million times smaller), 10⁶ mm = 1 m
4. nano (billion times smaller), 10⁹ nm = 1m
5. Hum, how do you put 10⁹ into your calculator???  Well you have to put it in as "1 EE 9"  NOT 10 ^ 9.
3. Scientific Notation (Exponential Notation) (Important)
1. Used for really big and small numbers
1. 84,000,000,000 = 8.4 x 10¹⁰
2. 0.000000441 = 4.41 x 10^-7
3. 663 = 6.63 x 10²
4. 0.15 = 1.5 x 10¹
5. 9.9 = 9.9 x 10⁰
6. Need help - see Appendix A in your book
2. 8.4 x 10¹⁰ in your calculator is 8.4 EE 10
3. 4.41 x 10^-7 in your calculator is 4.41 EE -7
4. Measurements must have units or its wrong.
6. Mass
1. Mass = amount of matter
2. Matter = has volume and takes up space
3. Can you think of something that is not matter?  
7. Length
1. meter (m) is about 39 inches or 3 inches more than a yard
2. centimeter (cm) is about the width of a finger
3. millimeter (mm) is about the thickness of a dime
4. kilometer (km) is about 0.6 miles or a little more than 1/2 a mile
8. Temperature
1. Remember this is an intensive property
2. degrees Fahrenheit (^oF) - US uses this scale. 
3. degrees Celsius (^oC) - everyone else uses this scale
4. Kelvin (K) - scientists use this
5. Conversions - you must be able to convert between these different scales (Important)
1. ^oC + 273 = K
2. ^oF = (9/5) ^oC + 32
3. Try these:
1. Phoenix hit 118 ^oF this summer.  What is that in ^oC and K?
2. We have been able to get to 0.45K in lab. What is that in ^oC and ^oF?
4. Answers:
1. 48^oC and 321 K
2. -273^oC and -459^oF
9. Volume
1. Surface Area (SA) = length x width so units are something like m² or cm² or in² or miles²
2. Volume = length x width x height so units are something like m³ or cm³ or in³ or miles³
3. Note a cubic centimeter = cm³ which is a cc (medecine) which is a mL (Important)
4. Try this - what is the volume of a rectangle with sides measuring 3.2, 2.5, and 1.8 inches?  Answer:  14 in³
10. Density
1. An intensive property.  The density of water is the SAME whether you have a cup of water or a bathtub full of water as long as the temperature is the same.  
2. d = m / V  so units are (g/mL) unless otherwise specified.  Notice this is a ratio - ratios are conversions factors. (Important)
3. Which has more mass - 15 grams of solid gold or 15 grams of helium gas???  Hum.     Yep they have the same mass - 15 grams.  Did I get ya?  How about this - which is more dense???   Hum.   The gold - 15 g of gold will take up a lot less space than 15 g of gas.
4. In general:  d(s) > d(l) >> d(g)  Check out some values in Table 1.6.  Here are some more densities in g/mL 

gasoline	0.70	U	18.9	Pt	21.45
Hg	13.546	Nitrogen gas	0.001251	diamond	3.53
Fe	7.86	Carbon monoxide	0.00125	manure	0.4

5. Water is weird in that ice floats in water.  Most solids sink in their liquids.  Thank goodness ice floats on water or when it gets cold lakes and oceans would freeze from the bottom up this life would die and we would not be here! 
6. When you heat something up matter expands (ice excepted).  Does that mean the atoms get bigger???  No, the atoms move faster and push apart a little bit thus taking up more space.  When you cool something down matter contracts.  Do the atoms get smaller???  No, the atoms move less and don't bump each other apart as much. Check it out here.
7. Try these problems:
1. Nurse Chapel's diamond fell off her ring into a syringe of saline solution and she noticed the water level rose by 1.4 cc.  How much does her diamond mass?
2. How much space would 15 grams of carbon monoxide occupy in liters?
8. Answers: (but try them first before looking!!!)
1. 1.4 mL (3.53 g / mL) = 5.0 grams
2. 15 g CO ( mL / 0.00125 g)( L / 1000 mL)  = 12 L
10. Accuracy, Precision, and XII. Significant Digits or Figures (sig dig)
1. accuracy = close to the real value, or the average is close to the real value.  Weighing a paperclip on a bathroom scale would not be very accurate as it would barely move and you could not get a good reading in pounds.   
2. precision = values close to each other, the machine or device measures the same way every time but not sure if it is right.  Like the bathroom scale that is always off by 5 pounds - consistent, but wrong
3. Both is best - accurate and precise.  

accurate	precise	accurate and precise

4. In lab and in the real world you should measure everything as accurately as possible PLUS estimate one more digit.
5. Significant Digit rules and examples. Go to chm 151 and click on sig dig (Super Important)
6. What if all digist in 1200 are significant?  How do you express that?  Well you write in scientific notation.  1200 has 2 sig dig while 1.200 x 10³ has 4 sig dig.
11. Sig figs discussed above
12. Rounding 
1. 5 round up, 4 stays the same (keep it simple)
2. Let's say you are calculating density by dividing 3.4 grams by 1.3 mL and the calculator says 2.615384.  Hum.  Wow that answer has a lot of digits considering our original measurements only had two each.  Well your calculator is stupid - you must determine that the answer can only have 2 sig dig as well and must round.  The answer is really 2.6 g/mL.
3. Answers can NOT be more significant than the measurements in the problem.
4. Multiplication and Division - answer must have same sig dig as the least significant number in the problem
5. Addition and subtraction - answer must have same decimal places as the least decimal places number in the problem
6. Examples of calculations Go to chm 151 and click on sig dig
7. Remember to never round until your FINAL answer or you'll get rounding errors for rounding at each step.
13. Conversions  (Super Important)
1. Use ratios as conversion factors.  (This is called dimensional analysis - fancy smancy name) Example - you know there are 3 feet in 1 yard so the ratios are ( 3 ft / 1 yd)  or  (1 yd / 3 ft). 
2. English to Metric and vice versa.  We will give you conversions for English to metric units like 1 meter = 1.61 km,  1 inch = 2.54 cm,  and 1 kg = 2.20 pounds.  
1. How many yards are in 789 cm?  With the conversions given above I'd set this problem up like 789 cm ( 1 in / 2.54 cm)(1 ft / 12 in)( 1 yd / 3 ft) = 8.63 yards
2. More examples here. Go to chm 151 and click on conversions
3. Metric to Metric units.  We will NOT give you conversions - you must know your metric prefixes listed above. Always go to the base unit first.
1. 87.24 mm = ? Mm   Hum.  Try it before looking further.  You must be able to do these on your own, not just follow me along. Also go to meters first before megameters.  OK the answer - 87.24 mm ( 1 m / 1000 mm)( 1 Mm / 10⁶ m) = 8.724 x 10^-8 Mm
2. More examples here. Go to chm 151 and click on conversions
4. Common sense - don't leave it behind!  Make sure your answers make sense.  For example -3.4 K makes no sense because Kelvin's lowest temperature is zero!  Saying a truck weighs 0.425 grams makes no sense.  Saying a molecule ways 2.5 kg makes no sense.
5. In solving all problems, look at what you are given.  Decide what information is useful.  Look for conversions.  Identify your given units and the units you need.  Find a way to get from the given units to the needed units.  It's all about the units.