Unit 1 Introduction to Chemistry Internet web site: http://old.unit5.org/roller/

Material Safety Data Sheet (MSDS) -- gives information about a chemical -- lists “Dos” and “Don’ts;” emergency procedures

a one-time exposure that causes damage Chemical Exposure acute exposure vs. chronic exposure a one-time exposure that causes damage damage occurs after repeated exposure e.g. reaction to drugs or medication e.g. smoking, asbestos

How Toxic is “Toxic?” Chemicals may cause harm in many different ways: Flammable Explosive Radioactive Corrosive Irritant Carcinogenic Mutagenic Teratogenic

LD50 the lethal dosage for 50% of the animals on which the chemical is tested There are various ways an LD50 can be expressed. For example, acetone has the following LD50s: ORL-RAT LD50: 5,800 mg/kg IHL-RAT LD50: 50,100 mg/m3h SKN-RBT LD50: 20 g/kg

LD50 Example Chemical A: LD50 = 3.2 mg/kg Chemical B: LD50 = 48 mg/kg Which is more toxic? Chemical A is more toxic because LESS is necessary to kill half of a given population

Science

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 NASA’s Problem Design a material Corning Glass Company that is clear and can with- stand extreme differences in temperature without fail- ing (cracking). Design a face shield to protect and provide clear vision. Corning Glass Company FAILED…but SUCCEEDED at making great cookware that can withstand extremes in temperature. Often times in science, great discoveries are made serendipitously or by accident. People set out with a goal in mind and discover something else, quite remarkably.

Aluminum Mining 1850s: aluminum sold for $500 / lb Charles Martin Hall 4-6 pounds bauxite current 1 lb Al + = 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 Charles Martin Hall (1863 - 1914) was motivated by a professor at Oberlin College who remarked that anyone discovering a cheap method of producing aluminum would become rich and famous. Hall's discovery, in his home laboratory within eight months of his graduation, was the foundation of the aluminum industry in the United States. Paul Heroult (1863 - 1914) a student of LeChatelier's, was, like Hall, 23 years old when he discovered the same method of producing aluminum. Heroult's discovery was the foundation of the aluminum industry in Europe. Earth's crust is ~8.3% by mass of aluminum. This makes aluminum the third most abundant element and the most abundant metal. Aluminum metal was not isolated until 1825, when Hans Oersted produced it in a pure form. It was considered a semi-precious metal (rare and expensive) in 1884 when an aluminum cap was placed on the Washington monument.

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. observation inference uses the five senses involves a judgment or an assumption

Observations are also called data. Types of Data Observations are also called data. qualitative data quantitative data -- descriptions -- measurements e.g., colorless liquid e.g., 17 mL; 83oC (vs. clear liquid)

Candle Observation Activity This cartoon is used the day after we perform the "Observations of a Burning Candle Lab" for a humorous set induction.

A Description of a Burning Candle A photograph of a burning candle is shown1 in the upper right corner. The candle is cylindrical2 and has a diameter3 of about 3 cm. The length of the candle was initially about 16 centimeters4, and it changed slowly5 during observation, decreasing about 1 cm in one hour6. The candle is made of a translucent7, white8 solid9 which has a slight odor10 and no taste11. It is soft enough to be scratched with the fingernail12. There is a wick13 which extends from top to bottom14 of the candle along its central axis15 and protrudes about 5 mm above the top of the candle16. The wick is made of three strands of string braided together17. 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 wick18. The burning candle makes no sound19. While burning, the body of the candle remains cool to the touch20 except near the top. Within about 1.5 cm of the top the candle is warm21 (but not hot) and sufficiently soft to mold easily22. The flame flickers in response to air currents23 and tends to become quite smoky while flickering24. In the absence of air currents, the flame is of the form shown in the photograph, though it retains some movement at all times25. The flame begins about 2 mm above the top of the candle26, and at its base the flame has a blue tint27. Immediately around the wick in a region about 2 mm wide and extending about 5 mm above the top of the wick28 the flame is dark29. This dark region is roughly conical in shape30. Around this zone and extending about 1 cm above the dark zone is a region which emits yellow light31, bright but not blinding32. The flame has rather sharply defined sides33 but a ragged top34. The wick is white where it emerges from the candle35, but from the base of the flame to the end of the wick36 it is black, appearing burnt, except for the last 0,5 cm, where it glows red37. The wick curls over about 3 mm from its end38. As the candle becomes shorter, the wick shortens too, so as to extend roughly a constant length above the top of the candle39. Heat is emitted by the flame40, enough so that it becomes uncomfortable in 10 to 20 seconds if one holds his finger 10 cm to the side of the quiet flame41 or 10 – 12 cm above the flame42. Burning a Candle “Wax is a mixture of compounds containing chiefly carbon and hydrogen. When the wick is lit, some wax is drawn up the wick and vaporizes. The vapor burns, using oxygen in the air. The yellow part of the flame is caused by carbon particles incandescing (glowing) at high temperatures. Unburned carbon forms soot.” Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 30

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 (i.e., a recipe of what was done) variable: any factor that could influence the result

A Scientific Experiment Experiments must be controlled: Only one variable can change at a time Independent variable: a variable you control and manipulate (x-axis) Dependent variable: the variable you measure as you change I.V. (y-axis) conclusion: must be supported with evidence from the data collected

A Controlled Experiment?

Scientific Method Make observation Ask question Develop hypothesis Test hypothesis with an experiment Test hypothesis with further experiments Revise hypothesis Analyze data and draw conclusions Hypothesis IS supported Hypothesis is NOT supported Develop theory Wysession, Frank, Yancopoulos, Physical Science Concepts in Action, 2004, page 8

Scientific Law vs. Scientific Theory states what happens, i.e., a relationship between various quantities -- Laws are often written in the form of… an equation. -- e.g., Newton’s law of gravity, laws of conservation

a scanning tunneling microscope (STM) theory: tries to explain WHY or HOW something happens -- based on current evidence -- e.g., Theory of Gravity, Atomic Theory 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)

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Chemistry

The Greeks believed there were four elements The Beginning Early practical chemistry: household goods, weapons, soap, wine, basic medicine The Greeks believed there were four elements ~ D ___ D D ___ earth wind fire water

Allegedly, this substance would turn cheap metals into gold Alchemy (~500 – 1300 C.E.) the quest for the Philosopher’s Stone (the elixir, the Sorcerer’s Stone) Allegedly, this substance would turn cheap metals into gold Alchemical symbols for substances… . . . . . . . . . . . . . . . GOLD SILVER COPPER IRON SAND

changing one substance into another transmutation: changing one substance into another COPPER GOLD  Philosopher’s Stone In ordinary chemical reactions… we cannot transmute elements into different elements

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 biochemistry the study of carbon containing compounds the chemistry of living things inorganic physical studies everything except carbon e.g., compounds containing metals measuring physical properties of substances 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 bulk chemical manufacturing acids, bases, fertilizers **sulfuric acid (H2SO4) = #1 chemical petroleum products fuels, oils, greases, asphalt pharmaceuticals 1 in 10,000 new drugs gets FDA approval synthetic fibers nylon, polyester, rayon , spandex

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: environment worker EPA OSHA consumer OSHA: Occupational Safety and Health Admin. CPSC: Consumer product safety commission FDA USDA CPSC

Manipulating Numerical Data

Graphs

shows how many of something are in each category Bar Graph shows how many of something are in each category # of students

shows how a whole is broken into parts Pie Graph shows how a whole is broken into parts Percentage of Weekly Income

shows continuous change Line Graph shows continuous change Stock Price over Time In chemistry… you will always use a line graph.

Elements of a “good” line graph 1. title 2. axes labeled, with units 3. neat 4. use the available space

Graphing HW Time Total Dist. cycled (km) 8 a.m. 9 a.m. 12 10 a.m. 23 11 a.m. 33 noon 42 1 p.m. 50 2 p.m. 57 3 p.m. 63 4 p.m. 68 Distance Cycled (km) Time (h) 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 10exponent 800 = 8 x 10 x 10 = 8 x 102 2531 = 2.531 x 10 x 10 x 10 = 2.531 x 103 0.0014 = 1.4 10 10 10 = 1.4 x 10–3 (-) exponent = number < 1 (+) exponent = number > 1

Put in standard form 1.87 x 10–5 = 0.0000187 3.7 x 108 = 370,000,000 7.88 x 101 = 78.8 2.164 x 10–2 = 0.02164 Change to scientific notation 12,340 = 1.234 x 104 0.369 = 3.69 x 10–1 0.008 = 8 x 10–3 1,000,000,000 = 1 x 109 6.02 x 1023 = 602,000,000,000,000,000,000,000

Using the Exponent Key EE EXP

The EE or EXP or E key means “times 10 to the…” How to type out 6.02 x 1023: How to type out 6.02 x 1023: 6 EE . 3 2 6 EE . 3 2 not… WRONG! 6 y x . 3 2 WRONG! or… x 1 6 . 2 EE 3 and not… TOO MUCH WORK. y x 3 2 x 1 6 .

Also, know when to hit your (–) sign. (before the number, after the number, or either one)

1.2 x 105 2.8 x 1019 = 1 . 2 EE 5 9 8 Type this calculation in like this: 4.2857143 –15 Calculator gives… 4.2857143 E–15 or… This is NOT written… 4.3–15 But instead is written… 4.3 x 10–15 or 4.3 E –15

7.5 x 10–6 (–8.7 x 10–14) = –6.5 x 10–19 4.35 x 106 (1.23 x 10–3) = 5.35 x 103 or 5350 5.76 x 10–16 9.86 x 10–4 = 5.84 x 10–13 8.8 x 1011 x 3.3 x 1011 = 2.9 x 1023

Accuracy and Precision All numerical data are the result of uncertain measurements. precision: a measure of the degree of fineness of a measurement; it depends on the extent to which the instrument is calibrated e.g., 8 m vs. 8.00 m vs. 8.00000 m

When repeated, precise measurements yield similar answers each time. e.g., precise… 0.653 m 0.652 m 0.654 m imprecise… 0.7 m 0.8 m 0.6 m A good rule of thumb is… It is the % difference that is important.

Three types of error can affect accuracy. how close a measured value is to the true value Three types of error can affect accuracy. human error: mistake in reading instrument or recording results -- minimize with repeated measurements method error: using measuring instrument improperly e.g., parallax in measuring with a meter stick instrument error: measuring device is improperly calibrated e.g., bathroom scale that always reads 5 lbs. too heavy

Significant Figures about… A student is combining separate water samples, all of differing volumes, into one large bucket. Samples A, B and C are 25.5 mL, 16.37 mL and 51 mL, respectively. Once combined, what is the total volume of all the samples? 92.87 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.

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…) 26 60 50 25 16.4 16.3

Identifying Significant Figures Counting SF in a number Non-zero numbers: ALWAYS count as SF Zeroes Left: NEVER count as SF (0.000345) 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 = 6.022 x 1023) Conversions (1 in = 2.54 cm) Relative to the non-zero numbers

How many Sig Figs? Measurement Number of SF Measurement Number of SF 2 0.030 kg 1.240560 x 106 mg 6 x 104 sec 246.31 g 20.06 cm 1.050 m 2 7 1 5 4 0.12 kg 1240560. cm 6000000 kg 6.00 x 106 kg 409 cm 29.200 dm 0.02500 g 2 7 1 3 5 4 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) 11.31 + 33.264 + 4.1 = 48.674 Multiplication/Division Round the answer to the smallest number of SF found 5.282 x 3.42 = 18.06444 → 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, 16.37 mL and 51 mL, respectively. Once combined, what is the total volume of all the samples? 25.5 mL + 16.37 mL + 51 mL = 92.87 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. 75.6 0.528396 387600 4200 8.4845E-4 76 75.6 75.600 0.53 0.528 0.52840 390,000 388,000 * 3.8760 x 105 4,200 * 4.20 x 103 4.2000 x 103 8.5 x 10–4 8.48 x 10–4 8.4845 x 10–4 * = requires scientific notation

Units must be carried into the answer, unless they cancel. 5.2 kg (2.9 m) (18 s)(1.3 s) = kg*m s2 0.64 4.8 g (23 s) (18 s)(37 s) = g s 0.17

x + y = z x + y = z – y – y x = z – y Solve for x. x and y are connected by addition. Separate them using subtraction. In general, use opposing functions to separate things. x + y = z – y – y The +y and –y cancel on the left, x = z – y leaving us with…

Numerical Example x – 24 = 13 x – 24 = 13 +24 +24 x = 37 Solve for x. x and 24 are connected by subtraction. Separate them using the opposite function: addition. x – 24 = 13 +24 +24 The –24 and +24 cancel on the left, leaving us with… x = 37

( ) F = k x __ 1 k F = k x (or) F = k x k x = F k __ Solve for x. x and k are connected by multiplication. Separate them using the opposite function: division. (or) F = k x k The two k’s cancel on the right, leaving us with… x = F k __

( ) Numerical Example 8 = 7 x __ 1 7 8 = 7 x (or) 8 = 7 x 7 x = 8 7 __ Solve for x. 8 = 7 x ( ) __ 1 7 8 = 7 x x and 7 are connected by multiplication. Separate them using the opposite function: division. (or) 8 = 7 x 7 The two 7’s cancel on the right, leaving us with… x = 8 7 __

( ) ___ x BA = TR H BAH = xTR 1 TR ___ BAH = xTR ___ BAH TR x = Solve for x. ___ x BA = TR H One way to solve this is to cross-multiply. BAH = xTR 1 TR ( ) ___ Then, divide both sides by TR. BAH = xTR ___ BAH TR x = The answer is…

( ) ____ T1 P1V1 = P2V2 T2 1 ____ P1V1T2 = P2V2T1 T2 = P1V1 ______ Solve for T2, where… P1 = 1.08 atm P2 = 0.86 atm V1 = 3.22 L V2 = 1.43 L T1 = 373 K ____ T1 P1V1 = P2V2 T2 1 P1V1 ( ) ____ P1V1T2 = P2V2T1 T2 = P1V1 ______ P2V2T1 T2 = (1.08 atm)(3.22 L) _____________________ (0.86 atm)(1.43 L)(373 K) = 130 K

You will be responsible for knowing these! SI Prefixes kilo- (k) 1000 deci- (d) 1/10 centi- (c) 1/100 milli- (m) 1/1000 Also, 1 mL = 1 cm3 and 1 L = 1 dm3 You will be responsible for knowing these!

Conversion Factors and Unit Cancellation

How many cm are in 1.32 meters? equality: 1 m = 100 cm (or 0.01 m = 1 cm) conversion factors: ______ 1 m 100 cm ______ 1 m 100 cm or 1.32 m 1 m 100 cm = 132 cm We use the idea of unit cancellation to decide upon which one of the two conversion factors we choose.

Again, the units must cancel. How many m is 8.72 cm? equality: 1 m = 100 cm conversion factors: ______ 1 m 100 cm ______ 1 m 100 cm or 8.72 cm 1 m 100 cm = 0.0872 m Again, the units must cancel.

How many kilometers is 15,000 decimeters? 15,000 dm 10 dm 1 m 1,000 m 1 km 1.5 km =

How many seconds is 4.38 days? ____ ( ) ( ) _____ ( ) ____ 24 h 1 d 1 h 60 min 1 min 60 s 4.38 d = 378,432 s If we are accounting for significant figures, we would change this to… 3.78 x 105 s

4. Convert 41.2 cm2 to mm2 Recall that… 1 cm = 10 mm ( )2 ( )2 ( )2 ( )2 41.2 cm2 1 cm2 102 mm2 = 4,120 mm2

SI-US Conversion Factors Equality Conversion Factors Length 2.54 cm 1 in 1 in 2.54 cm 2.54 cm = 1 in. and 39.4 in 1 m 1 m 39.4 in. 1 m = 39.4 in. and Volume 946 mL 1 qt 1 qt 946 mL 946 mL = 1 qt and 1.06 qt 1 L 1 L 1.06 qt and Dominoes Activity 1 L = 1.06 qt Mass 453.6 g 1 lb 1 lb 453.6 g 453.6 g = 1 lb and 2.20 lb 1 kg 1 kg 2.20 lb 1 kg = 2.20 lb and

Simple Math with Conversion Factors

( ) ( ) ______ ______ Find area of rectangle. A = L . W 4.6 cm = (4.6 cm)(9.1 cm) 9.1 cm = 42 cm 2 . cm cm.cm ( ) ______ 100 cm 1 m Convert to m2. 42 cm2 2 = 0.0042 m2 ( ) ______ 1 cm 10 mm Convert to mm2. 42 cm2 2 = 4200 mm2

For the rectangular solid: Length = 14.2 cm Width = 8.6 cm Height = 21.5 cm Find volume. V = L . W . H = (14.2 cm)(8.6 cm)(21.5 cm) = 2600 cm3

( ) ______ Convert to mm3. 1 cm 10 mm 2600 cm3 3 = 2,600,000 mm3 = 2.6 x 106 mm3 mm and cm differ by a factor of………. mm2 “ cm2 “ “ “ “ “ ………. mm3 “ cm3 “ “ “ “ “ ………. 10 100 1000

Density  how tightly packed the particles are m V D Density = Typical units: g/cm3 for solids g/mL for fluids Glass: liquid or solid? liquids and gases

To find volume, use… 1. a formula V = p ∙ r2 ∙ h V = l ∙ w ∙ h 2. water displacement V = ? Vfinal Vinitial Vobject = Vfinal – Vinitial

Things that are “less dense” float in things that are “more dense.” ** Density of water = 1.0 g/mL = 1.0 g/cm3 Things that are “less dense” float in things that are “more dense.” (And things that are “more dense” sink in things that are “less dense.” D < 1 g/cm3 D > 1 g/cm3 D < 1 g/cm3 D < 1 g/cm3 The density of a liquid or solid is nearly constant, no matter what the sample’s temperature Density of gases is highly dependent on temperature

Ironwood Trees Several different varieties of hardwood trees, having densities between 1.34 and 1.49 g/cm3 Most dense species is South African Ironwood (black ironwood) Olea laurifolia Found in Florida and West Indies D = 1.49 g/cm3

Will Bowling Balls sink or float in H2O? If DBB > 1, it will sink If DBB < 1, it will float 21.6 cm in diameter Vsphere = 4/3 p r3 V = 4/3 p (10.8 cm)3 m V D V = 5,276.7 cm3 m = D V m = (1.00 g/cm3)(5276.7 cm3) m = 5276.7 g Since the mass of a BB varies, let’s figure out at what mass it will sink v. float …or 11.6 lbs

Density Calculations 1. A sample of lead (Pb) has mass 22.70 g and volume 2.000 cm3. Find sample’s density. m V D = 11.35 2. Another sample of lead occupies 16.2 cm3 of space. Find sample’s mass. V m = D V = 184 g

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/cm3. How much would it mass? Indy replaces the idol with a bag of sand (density = 2.5 g/cm3). 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 cm3 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 V = p r2 h = p (1.8 cm)2(1.5 cm) = 15.268 cm3 = 7.79

this object sink in water? m 8.2 cm 5.1 cm 4.7 cm 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? (Find the object’s density and compare it to water’s density.) m V D V = l w h = 8.20 cm (5.10 cm)(4.70 cm) = 196.55 cm3 = 0.778 < 1 No; it floats.

D5 D4 D3 D2 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? D1 1. Bulbs have essentially fixed masses and volumes. Therefore, each bulb has a fixed density. D2 D3 D4 2. The surrounding liquid has a fixed mass, but its volume is extremely temperature-dependent. D5

Dliq D5 Vliq D4 D3 D2 3. The density of the liquid can be written as… so… …if the liquid is cold: …but if it’s hot: Dliq mliq mliq = = Dliq Vliq Vliq On a cold morning, where are the bulbs? AT THE TOP

Osmium 76Os  

Basic Concepts in Chemistry

“what you started with” 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” reactants products

Reactants Products carbon dioxide methane + oxygen  + water CH4(g) + 2 O2(g)  CO2(g) + H2O(g) 2 

Reactants Products sodium hydroxide sodium + water  hydrogen + 2 Na(s) + 2 H2O(l)  H2(g) + 2 NaOH(aq) 

Law of Conservation of Mass: 2 Cu + H2O + CO2 + O2  CuCO3 + Cu(OH)2 Copper “patina” is a mixture of copper(II) carbonate and copper(II) hydroxide. It has a characteristic green color. total mass total mass of products of reactants = Pmass = Rmass

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

A proposed organic synthesis of tetrahydrocannabinol (THC) putting simpler substances together, usually in many steps, to make something more complex A proposed organic synthesis of tetrahydrocannabinol (THC)