Presentation on theme: "Unit 1 Introduction to Chemistry Internet web site:"— Presentation transcript:
Unit 1 Introduction to Chemistry Internet web site:
Material Safety Data Sheet (MSDS) gives information about a chemical -- lists “Dos” and “Don’ts;” emergency procedures --
Chemical Exposure a one-time exposure that causes damage acute exposure vs.chronic exposure damage occurs after repeated exposure reaction to drugs or medication e.g. smoking, asbestos
How Toxic is “Toxic?” Flammable Explosive Radioactive Corrosive Irritant Carcinogenic Mutagenic Teratogenic Chemicals may cause harm in many different ways:
the lethal dosage for 50% of the animals on which the chemical is tested LD 50 There are various ways an LD 50 can be expressed. For example, acetone has the following LD 50 s: ORL-RAT LD 50 : 5,800 mg/kg IHL-RAT LD 50 : 50,100 mg/m 3 h SKN-RBT LD 50 : 20 g/kg
LD 50 Example Which is more toxic? Chemical A is more toxic because LESS is necessary to kill half of a given population Chemical A: LD 50 = 3.2 mg/kg Chemical B: LD 50 = 48 mg/kg
The Functions of Science pure science applied science the search for knowledge; facts using knowledge in a practical way e.g., properties of aluminum strong lightweight good conductor
Corning Glass Corning Glass Company FAILED…but SUCCEEDED at making great cookware that can withstand extremes in temperature. Design a face shield to protect and provide clear vision.
Aluminum Mining 1850s: aluminum sold for $500 / lb Charles Martin Hall Developed method to extract aluminum from bauxite Hall’s method –As a result, $0.30/lb 4-6 pounds bauxite current1 lb Al + =
Science attempts to establish cause/effect relationships Science can NEVER prove a cause/effect relationship, only make a correlation…
risk-benefit analysis weigh pros and cons before deciding Because there are many considerations for each case, “black/white thinking” rarely applies. It is usually shades of grey.
How does scientific knowledge advance? 1. curiosity 2. determination 3. persistence 4. good observations
The Scientific Method
** Key: Be a good observer. observationinference involves a judgment or an assumption uses the five senses
Types of Data Observations are also called data. qualitative data quantitative data colorless liquid e.g.,e.g., descriptionsmeasurements 17 mL; 83 o C (vs. clear liquid)
Candle Observation Activity
A Description of a Burning Candle A photograph of a burning candle is shown 1 in the upper right corner. The candle is cylindrical 2 and has a diameter 3 of about 3 cm. The length of the candle was initially about 16 centimeters 4, and it changed slowly 5 during observation, decreasing about 1 cm in one hour 6. The candle is made of a translucent 7, white 8 solid 9 which has a slight odor 10 and no taste 11. It is soft enough to be scratched with the fingernail 12. There is a wick 13 which extends from top to bottom 14 of the candle along its central axis 15 and protrudes about 5 mm above the top of the candle 16. The wick is made of three strands of string braided together 17. A candle is lit by holding a source of flame close to the wick for a few seconds. Thereafter the source of flame can be removed and the flame sustains itself at the wick 18. The burning candle makes no sound 19. While burning, the body of the candle remains cool to the touch 20 except near the top. Within about 1.5 cm of the top the candle is warm 21 (but not hot) and sufficiently soft to mold easily 22. The flame flickers in response to air currents 23 and tends to become quite smoky while flickering 24. In the absence of air currents, the flame is of the form shown in the photograph, though it retains some movement at all times 25. The flame begins about 2 mm above the top of the candle 26, and at its base the flame has a blue tint 27. Immediately around the wick in a region about 2 mm wide and extending about 5 mm above the top of the wick 28 the flame is dark 29. This dark region is roughly conical in shape 30. Around this zone and extending about 1 cm above the dark zone is a region which emits yellow light 31, bright but not blinding 32. The flame has rather sharply defined sides 33 but a ragged top 34. The wick is white where it emerges from the candle 35, but from the base of the flame to the end of the wick 36 it is black, appearing burnt, except for the last 0,5 cm, where it glows red 37. The wick curls over about 3 mm from its end 38. As the candle becomes shorter, the wick shortens too, so as to extend roughly a constant length above the top of the candle 39. Heat is emitted by the flame 40, enough so that it becomes uncomfortable in 10 to 20 seconds if one holds his finger 10 cm to the side of the quiet flame 41 or 10 – 12 cm above the flame 42.
Parts of the Scientific Method Identify an unknown. Make a hypothesis: a testable prediction Repeatedly experiment to test hypothesis. procedure: order of events in experiment variable: any factor that could influence the result (i.e., a recipe of what was done)
A Scientific Experiment conclusion: must be supported with evidence from the data collected Experiments must be controlled: Only one variable can change at a time Independent variable: Dependent variable: a variable you control and manipulate (x-axis) the variable you measure as you change I.V. (y-axis)
A Controlled Experiment?
Make observation Ask question Develop hypothesis Develop hypothesis Test hypothesis with an experiment Test hypothesis with an experiment Analyze data and draw conclusions Analyze data and draw conclusions Hypothesis IS supported Hypothesis IS supported Hypothesis is NOT supported Hypothesis is NOT supported Develop theory Develop theory Test hypothesis with further experiments Test hypothesis with further experiments Revise hypothesis Revise hypothesis Wysession, Frank, Yancopoulos, Physical Science Concepts in Action, 2004, page 8 Scientific Method
Scientific Law vs. Scientific Theory law: states what happens, i.e., a relationship between various quantities -- e.g., Newton’s law of gravity, --Laws are often written in the form of… an equation. laws of conservation
Theory of Gravity, Atomic Theory tries to explain WHY or HOW something happens theory: -- e.g., -- based on current evidence images of nickel atoms taken by an STM a scanning tunneling microscope (STM)
Phlogiston Theory of Burning 1. Flammable materials contain phlogiston 2. During burning, phlogiston is released into the air 3. Burning stops when… …object is out of phlogiston, or …the surrounding air contains too much phlogiston. (superceded by combustion theory of burning)
Rob L. Brown, Sr Tampa Avenue, Apt. J-432 Bloomington, Illinois Pay to the Order of $ ________________________________ Dollars Illinois State Bank CHICAGO, ILLINOIS Memo ________________ ___________________________ Date _________ : : Rob L. Brown, Sr. or Mary H. Brown 1007 Shady Lane Normal, Illinois Pay to the Order of $ ________________________________ Dollars NATIONAL CITY BANK OF MICHIGAN/ILLINOIS SPRINGFIELD, ILLINOIS Memo ________________ ___________________________ Date _________ : : Blank Checks
The Beginning The Greeks believed there were four elements Early practical chemistry: household goods, weapons, soap, wine, basic medicine earthwindfire water ~ ~ ___
Alchemy Allegedly, this substance would turn cheap metals into gold the quest for the Philosopher’s Stone (~500 – 1300 C.E.) (the elixir, the Sorcerer’s Stone) Alchemical symbols for substances… GOLDSILVERCOPPER IRONSAND
transmutation: we cannot transmute elements into different elements changing one substance into another COPPER GOLD Philosopher’s Stone In ordinary chemical reactions…
Alchemy was practiced in many regions of the world, including China and the Middle East. Alchemy arrived in western Europe around the year 500 C.E. Modern chemistry evolved from alchemy.
Contributions of alchemists: experimental techniques new glassware information about elements developed several alloys
What is chemistry? the study of matter and its changes
Areas of Chemistry organic physical inorganic biochemistry studies everything except carbon e.g., compounds containing metals the study of carbon containing compounds measuring physical properties of substances the chemistry of living things e.g., the melting point of gold
Careers in Chemistry research (new products) production (quality control) development (manufacturing) chemical sales software engineering teaching
The skills you will develop by an earnest study of chemistry will help you in any career field.
The Scope of Chemistry pharmaceuticals nylon, polyester, rayon bulk chemical manufacturing petroleum products synthetic fibers acids, bases, fertilizers fuels, oils, greases, asphalt 1 in 10,000 new drugs gets FDA approval spandex, **sulfuric acid (H 2 SO 4 ) = #1 chemical
Colloidal Silver Used to treat fungal infections, skin rashes, Lyme disease, HIV/Aids and food poisoning
OK Supplements Calcium, Cranberry, Fish Oil, Vitamin D, Lactobacilius
Chemistry impacts: everyone all fields of endeavor
Government Regulation of Chemicals The various levels of government regulate chemicals to protect the: OSHA worker FDA USDA CPSC consumer EPA environment
Manipulating Numerical Data
Bar Graph shows how many of something are in each category # of students
Pie Graph shows how a whole is broken into parts Percentage of Weekly Income
Line Graph shows continuous change Stock Price over Time you will always use a line graph. In chemistry…
Elements of a “good” line graph 2. axes labeled, with units 4. use the available space 1. title 3. neat
Graphing HW Time Total Dist. cycled (km) 8 a.m.0 9 a.m a.m a.m.33 noon42 1 p.m.50 2 p.m.57 3 p.m.63 4 p.m.68 Time (h) Distance Cycled (km) Extrapolation: predicting a pattern outside of a data set using the graph Interpolation: estimating a data point within the set of data using the pattern of the graph
Essential Math of Chemistry
Scientific Notation …used to express very large or very small numbers. Also used to maintain correct SF. Form:(# from 1 to 9.999) x 10 exponent 800= 8 x 10 x 10 = 8 x = x 10 x 10 x 10 = x = = 1.4 x 10 –3 (-) exponent = number < 1 (+) exponent = number > 1
Put in standard form 1.87 x 10 –5 = x 10 8 = 370,000, x 10 1 = x 10 –2 = Change to scientific notation 12,340 = x = 3.69 x 10 – = 8 x 10 –3 1,000,000,000 = 1 x x = 602,000,000,000,000,000,000,000
Using the Exponent Key EXPEE
The EE or EXP or E key means “times 10 to the…” How to type out 6.02 x : 6EE y x x EE320y x 32 x not… or… and not… How to type out 6.02 x : 6EE WRONG! TOO MUCH WORK.
Also, know when to hit your (–) sign. (before the number, after the number, or either one)
4.3 x 10 – E –15or 1.2 x x But instead is written… = 1. 2EE Type this calculation in like this: This is NOT written…4.3 – –15 Calculator gives… E–15 or…
–6.5 x 10 – x 10 3 or x x 10 –6 (–8.7 x 10 –14 ) = 4.35 x 10 6 (1.23 x 10 –3 ) = 5.76 x 10 – x 10 –4 = 8.8 x x 3.3 x = 5.84 x 10 –13
All numerical data are the result of uncertain measurements. 8 m Accuracy and Precision precision: a measure of the degree of fineness of a measurement; it depends on the extent to which the instrument is calibrated e.g.,vs mvs m
0.653 m When repeated, precise measurements yield similar answers each time. e.g., precise… imprecise… m m 0.7 m 0.8 m 0.6 m A good rule of thumb is… It is the % difference that is important.
accuracy:how close a measured value is to the true value Three types of error can affect accuracy. human error: method error: instrument error: -- minimize with repeated measurements e.g., parallax in measuring with a meter stick e.g., bathroom scale that always reads 5 lbs. too heavy mistake in reading instrument or recording results measuring device is improperly calibrated using measuring instrument improperly
Significant Figures A student is combining separate water samples, all of differing volumes, into one large bucket. Samples A, B and C are 25.5 mL, mL and 51 mL, respectively. Once combined, what is the total volume of all the samples? mL NO! Because the samples were each measured with a different level of precision, we must factor that into our calculations by identifying what are called significant figures. about…
Measurement and Precision The last digit of any measured number is assumed to be an estimate (uncertain) The second to last digit is assumed to be known with certainty A (25.5 mL)B (16.37 mL)C (51 mL) (think dashes…)
Identifying Significant Figures Counting SF in a number Non-zero numbers: ALWAYS count as SF Zeroes Left: NEVER count as SF ( ) Middle: ALWAYS count as SF (5001) Right: sometimes… w/ decimal point: count as SF (25.10) w/o decimal point: DO NOT count as SF (8200) Exact Numbers: IGNORE SF (assumed to have an infinite number of SF) Counts (28 students in this class) Constants (1 mol = x ) Conversions (1 in = 2.54 cm) Relative to the non-zero numbers
How many Sig Figs? Measurement Number of SF 25 g kg x 10 6 mg 6 x 10 4 sec g cm m 0.12 kg cm kg 6.00 x 10 6 kg 409 cm dm g Now, determine the # of SF in Part A and B of the Sci. Not. HW (5 min)
Sig Figs with Calculations Note: For any calculations, always perform the entire calculation without rounding, and then round the final answer. Addition/Subtraction Round the answer to the LEAST number of decimal places found (least precise) = Multiplication/Division Round the answer to the smallest number of SF found x 3.42 = → rounded to 48.7 → rounded to 18.1 (3.42 only has 3 SF)
Back to the original question… A student is combining separate water samples, all of differing volumes, into one large bucket. Samples A, B and C are 25.5 mL, mL and 51 mL, respectively. Once combined, what is the total volume of all the samples? 25.5 mL mL + 51 mL = mL 93 mL Could I write that as 93.0? NO!
Round to the correct number of significant figures. Calculator says… 2 sig. figs.3 sig. figs.5 sig. figs E * x ,000390, x 10 – x 10 3 * 4.20 x , x 10 – x 10 –4 * = requires scientific notation
Units must be carried into the answer, unless they cancel kg*m s2s2 5.2 kg (2.9 m) (18 s)(1.3 s) = 4.8 g (23 s) (18 s)(37 s) = 0.17 g s
Solve for x. x + y = z – y x = z – y x and y are connected by addition. Separate them using subtraction. In general, use opposing functions to separate things. The +y and –y cancel on the left, leaving us with…
Solve for x. x – 24 = x = 37 x and 24 are connected by subtraction. Separate them using the opposite function: addition. The –24 and +24 cancel on the left, leaving us with… Numerical Example
Solve for x. F = k x kk x = F k __ x and k are connected by multiplication. Separate them using the opposite function: division. () __1 k F = k x () __1 k (or) The two k’s cancel on the right, leaving us with…
Numerical Example Solve for x. 8 = 7 x 77 x and 7 are connected by multiplication. Separate them using the opposite function: division. () __1 7 8 = 7 x () __1 7 (or) The two 7’s cancel on the right, leaving us with… x = 8 7 __
Solve for x. ___ x BA = TR H ___ BAH = xTR One way to solve this is to cross-multiply. BAH = xTR Then, divide both sides by TR. The answer is… ___ BAH TR x = 1 TR () ___1 TR () ___
Solve for T 2, where… P 1 = 1.08 atm P 2 = 0.86 atm V 1 = 3.22 L V 2 = 1.43 L T 1 = 373 K P 1 V 1 T 2 = P 2 V 2 T 1 ____ T1T1 P1V1P1V1 = P2V2P2V2 T2T2 1 P1V1P1V1 () 1 P1V1P1V1 () T 2 = P1V1P1V1 ______ P2V2T1P2V2T1 130 T 2 = (1.08 atm)(3.22 L) _____________________ (0.86 atm)(1.43 L)(373 K) = K
SI Prefixes kilo-(k) 1000 deci-(d) 1 / 10 centi-(c) 1 / 100 milli-(m) 1 / 1000 Also, 1 mL = 1 cm 3 and 1 L = 1 dm 3 You will be responsible for knowing these!
Conversion Factors and Unit Cancellation
How many cm are in 1.32 meters? conversion factors: equality: or 1.32 m = 132 cm 1 m = 100 cm ______1 m 100 cm We use the idea of unit cancellation to decide upon which one of the two conversion factors we choose. ______ 1 m 100 cm 1 m 100 cm (or 0.01 m = 1 cm)
How many m is 8.72 cm? conversion factors: equality: or 8.72 cm = m 1 m = 100 cm ______1 m 100 cm Again, the units must cancel. ______ 1 m 100 cm 1 m 100 cm
How many kilometers is 15,000 decimeters? 15,000 dm = 1.5 km 1,000 m 1 km 10 dm 1 m
How many seconds is 4.38 days? = 378,432 s 1 h 60 min24 h 1 d1 min 60 s ____ ()() () _____ 4.38 d 3.78 x 10 5 s If we are accounting for significant figures, we would change this to…
4. Convert 41.2 cm 2 to mm cm 2 Recall that…1 cm = 10 mm =4,120 mm 2 1 cm mm 2 ( ) 2
SI-US Conversion Factors EqualityConversion Factors Length Volume Mass 2.54 cm = 1 in. 1 m = 39.4 in. 946 mL = 1 qt 1 L = 1.06 qt g = 1 lb 1 kg = 2.20 lb 1 in 2.54 cm 39.4 in 1 m 39.4 in. 946 mL 1 qt 946 mL 1.06 qt 1 L 1.06 qt g 1 lb g 2.20 lb 1 kg 2.20 lb 2.54 cm 1 in and
Simple Math with Conversion Factors
Find area of rectangle. A = L. W = (4.6 cm)(9.1 cm) 9.1 cm = 42cm 2. cm 4.6 cm Convert to m cm 2 () ______ 100 cm 1 m 2 = m 2 Convert to mm cm 2 () ______ 1 cm 10 mm 2 = 4200 mm 2 cm. cm
For the rectangular solid: Find volume. Length = 14.2 cm Width = 8.6 cm Height = 21.5 cm V = L. W. H = (14.2 cm)(8.6 cm)(21.5 cm) =2600cm 3
Convert to mm cm 3 () ______ 1 cm 10 mm 3 = 2,600,000 mm 3 = 2.6 x 10 6 mm 3 mm and cm differ by a factor of………. mm 2 “ cm 2 “ “ “ “ “ ………. mm 3 “ cm 3 “ “ “ “ “ ………
Density how tightly packed the particles are Density = Typical units: g/cm 3 for solids g/mL for fluids m V D liquids and gases Glass: liquid or solid?
To find volume, use… 1. a formula water displacement V = l ∙ w ∙ h V = ∙ r 2 ∙ h V = ? V final V initial V object = V final – V initial 2.
** Density of water = The density of a liquid or solid is nearly constant, no matter what the sample’s temperature 1.0 g/mL = 1.0 g/cm 3 Things that are “less dense” float in things that are “more dense.” D < 1 g/cm 3 Density of gases is highly dependent on temperature D < 1 g/cm 3 D > 1 g/cm 3 D < 1 g/cm 3 (And things that are “more dense” sink in things that are “less dense.”
Ironwood Trees Several different varieties of hardwood trees, having densities between 1.34 and 1.49 g/cm 3 Most dense species is South African Ironwood (black ironwood) Olea laurifolia Found in Florida and West Indies D = 1.49 g/cm 3
Will Bowling Balls sink or float in H 2 O? 21.6 cm in diameter V sphere = 4/3 r 3 V = 4/3 (10.8 cm) 3 V = 5,276.7 cm 3 If D BB > 1, it will sink If D BB < 1, it will float Since the mass of a BB varies, let’s figure out at what mass it will sink v. float m = (1.00 g/cm 3 )( cm 3 ) m V D m = g m = D V …or 11.6 lbs
Density Calculations 1. A sample of lead (Pb) has mass g and volume cm 3. Find sample’s density. m V D 2. Another sample of lead occupies 16.2 cm 3 of space. Find sample’s mass. m = D V= 184 = g V
Indiana Jones Density Watch the famous opening scene to Indiana Jones and the Raiders of the Lost Ark The “pure gold” idol has a density of 19.3 g/cm 3. How much would it mass? Indy replaces the idol with a bag of sand (density = 2.5 g/cm 3 ). Why did he activate the booby trap? How much sand should he have used? Did you see that toss at the end!? How much would the idol weigh in lbs? (2.2 lb per kg) 19,300 g 7,720 cm 3 or 7.72 L! 42.5 lbs!
3. A 119 g solid cylinder has radius 1.80 cm and height 1.50 cm. Find sample’s density. 1.5 cm 1.8 cm m V D m V = r 2 h = (1.8 cm) 2 (1.5 cm) = = 7.79 cm 3
4. A 153 g rectangular solid has edge lengths 8.20 cm, 5.10 cm, and 4.70 cm. Will this object sink in water? 8.2 cm 5.1 cm 4.7 cm m V D (Find the object’s density and compare it to water’s density.) m V = l w h = 8.20 cm (5.10 cm)(4.70 cm) = = cm 3 < 1 No; it floats.
Galilean Thermometer Problem On a cold morning, a teacher walks into a cold classroom and notices that all bulbs in the Galilean thermometer are huddled in a group. Where are the bulbs? At the top of the thermometer, at the bottom or elsewhere? 1. Bulbs have essentially fixed masses and volumes. Therefore, each bulb has a fixed density. 2. The surrounding liquid has a fixed mass, but its volume is extremely temperature-dependent. D1D1 D2D2 D3D3 D4D4 D5D5
D1D1 D2D2 D3D3 D4D4 D5D5 3. The density of the liquid can be written as… so… …if the liquid is cold:…but if it’s hot: m liq = On a cold morning, where are the bulbs? AT THE TOP V liq m liq D liq = V liq D liq
Osmium 76 Os
Basic Concepts in Chemistry
chemical: any substance that takes part in, or occurs as a result of, a chemical reaction *All matter can be considered to be chemicals or mixtures of chemicals. chemical reaction: a rearrangement of atoms such that… “what you started with” differs from “what you end up with” products reactants
Law of Conservation of Mass: total mass of productsof reactants P mass = R mass = 2 Cu + H 2 O + CO 2 + O 2 CuCO 3 + Cu(OH) 2 Copper “patina” is a mixture of copper(II) carbonate and copper(II) hydroxide. It has a characteristic green color.
Losing weight? Keeping the Law of onservation of mass in mind… When you lose weight, where does it go? Three ways, all of which involve excretion
synthesis: putting simpler substances together, usually in many steps, to make something more complex A proposed organic synthesis of tetrahydrocannabinol (THC)