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PHASE TRANSITIONS

Summary of the three States of Matter ALSO CALLED PHASES, HAPPENS BY CHANGING THE TEMPERATURE AND/OR PRESSURE OF A SUBSTANCE. GAS : total disorder; mostly empty space; particles have complete freedom of motion (vibrational, rotational, & translational); particles are very far apart.

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PHASE TRANSITIONS

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  1. Summary of the three States of MatterALSO CALLED PHASES, HAPPENS BY CHANGING THE TEMPERATURE AND/OR PRESSURE OF A SUBSTANCE. GAS:total disorder; mostly empty space; particles have complete freedom of motion (vibrational, rotational, & translational); particles are very far apart. • Cool or compress (increase pressure) a gas to make a liquid • Heat or reduce pressure of a liquid to make a gas LIQUID:Disorder; particles or clusters of particles are free to move relative to each other (vibrational & rotational); particles are relatively close to each other. • Cool or compress (increase pressure) a liquid to make a solid • Heat or reduce pressure of a solid to make a liquid SOLID:order ranges from amorphous(slightly disordered) to crystalline (ordered); particles are essentially in fixed positions (vibrational only); particles are close to each other.

  2. PHASE TRANSITIONS • Consider the following phase changes and properly fill-in the schematic shown below: • 1. condensation • 2. evaporation • 3. freezing • 4. melting • 5. sublimation • 6. deposition

  3. Physical Changes: The substance or mixture does not alter in atomic composition. Some Physical Changes are boiling, evaporation, condensation, freezing, melting, sublimation, and deposition. Associated with Physical Changes are Physical Properties like boiling or freezing point, density, hardness, and state of matter. H2O (l) H2O (g) Chemical Changes: The substance changes in its atomic composition, the atoms are rearranged and new substances are formed. 2 H2O (l) 2 H2 (g)+ O2(g)

  4. Vocabulary to Know: Matter Atom Molecule Element Compound Homogeneous Mixture Heterogeneous Mixture Extensive Property Intensive Property Physical Property Chemical Property Physical Change Chemical Change

  5. YES NO YES NO YES NO

  6. LABORATORY APPLICATIONS • Define the following: • 1. Filtration • 2. Distillation • 3. Chromatography • 4. Extraction • 5. Crystallization

  7. ELEMENTS to MEMORIZE Aluminum Al Manganese Mn Antimony Sb Mercury Hg Argon Ar Neon Ne Arsenic As Nickel Ni Barium Ba Nitrogen N Beryllium Be Oxygen O Boron B Palladium Pd Bromine Br Phosphorus P Calcium Ca Platinum Pt Carbon C Plutonium Pu Cesium Cs Potassium K Chlorine Cl Radium Ra Chromium Cr Radon Rn Cobalt Co Rubidium Rb Copper Cu Selenium Se Fluorine F Silicon Si Gallium Ga Silver Ag Germanium Ge Sodium Na Gold Au Strontium Sr Helium He Sulfur S Hydrogen H Tin Sn Iodine I Titanium Ti Iron Fe Tungsten W Krypton Kr Uranium U Lead Pb Xenon Xe Lithium Li Zinc Zn Magnesium Mg Zirconium Zr

  8. SIX STEPS OF THE SCIENTIFIC METHOD 1. State a problem 2. Collect Observations 3. Search for scientific laws to state a relationship between observed facts 4. Form a hypothesis or a temporary observation for an observed fact 5. Develop a theory that provides a general explanation for observations made over time 6. Modify a theory to fit new facts

  9. ACCURACY vs. PRECISION • Accurate & preciseinaccurate but precise • inaccurate & imprecise

  10. PRECISION AND ACCURACY • 1. Precision – refers to the degree of reproducibility of a measured quantity. • 2. Accuracy – refers to how close a measured value is to the accepted or true value. • Precise (not accurate) Accurate (not precise) Both Precise/Accurate

  11. MEASUREMENTSScientific Notation Many measurements in science involve either very large numbers or very small numbers (#). Scientific notation is one method for communicating these types of numbers with minimal writing. GENERIC FORMAT: # . # #… x 10# A negative exponent represents a number less than 1 and a positive exponent represents a number greater than 1. 6.75 x 10-3 is the same as 0.00675 6.75 x 103 is the same as 6750

  12. MEASUREMENTSSignificant Figures I. All nonzero numbers are significant figures. II. Zero’s follow the rules below. 1. Zero’s between numbers are significant. 30.09 has 4SF 2. Zero’s that precede are NOT significant. 0.000034 has 2SF 3. Zero’s at the end of decimals are significant. 0.00900 has 3 SF 4. Zero’s at the end without decimals are either. 4050 has either 4SFor 3SF

  13. SIGNIFICANT DIGITS WORKSHEET • 1. Nonzero integers. Nonzero integers always count as significant digits. • 1492 has ______ significant digits • 2. Zeros. There are three classes of zeros: • A. Zeros that precede all nonzero digits are NOT significant. • 0.00162 has ______ significant digits • B. Zeros between nonzero digits are significant. • 4.007 has ______ significant digits • C. Trailing zeros at the right end of the number are significant only if the number • contains a decimal point. • 200 has ______ significant digits • 200. has ______ significant digits • 200.0 has ______ significant digits • 200 has ______ significant digits • D. When writing in scientific notation, all digits count. • 2.370 x 10-3 has ______ significant digit • 3. Exact numbers can be assumed to have an infinite number of significant figures. • The “2” in the circumference of a circle (2r) formula has ______ significant digits

  14. MEASUREMENTSSignificant Figures & Calculations Significant figures are based on the tools used to make the measurement. An imprecise tool will negate the precision of the other tools used. The following rules are used when measurements are used in calculations. Adding/subtracting: The result should be rounded to the same number of decimal places as the measurement with the least decimal places. Multiplying/dividing: The result should contain the same number of significant figures as the measurement with the least significant figures.

  15. WORKSHOP INVOLVING SIGNIFICANT DIGITS 1. For addition and subtraction, the result has the same number of decimal places as the least precise measurement used in the calculation. Example: 12.11 18.0 + 1.013 2. For multiplication and division, the number of significant figures in the result is the same as the number in the measurement with the fewest significant digits. (a) 4.56 x 1.4 = ________ (b)(4.12 + 3.636) = _____ 5.7 NOTE: Rules for Rounding: 1. In a series of calculations, carry the extra digits through to the final result, then round off. 2. If the digit to be removed is: A. less than 5, the preceding digit stays the same. For example, 2.32 rounds to 2.3. B. equal to or greater than 5, the preceding digit is increased by 1. For example, 3.46 rounds to 3.5.

  16. DIMENSIONAL ANALYSIS • Unit Conversions • Common SI Prefixes: • Factor PrefixAbbreviation • 106MegaM • 103Kilok • 102Hectoh • 101Dekada • 10-1Decid • 10-2Centi c • 10-3Milli m • 10-6Micro • 10-9Nanon • 10-12 Picop

  17. MEASUREMENTS - METRIC 1. The mass of a young student is found to be 87 kg. How many grams does this mass correspond to? 2. How many meters are equal to 16.80 km? 3. How many cubic centimeters are there in 1 cubic meter? 4. How many nm are there in 200 dm? Express your answer in scientific notation. 5. How many mg are there in 0.5 kg?

  18. MEASUREMENTS Since two different measuring systems exist, a scientist must be able to convert from one system to the other. CONVERSIONS Length  1 in = 2.54 cm  1 mi = 1.61 km Mass  1 lb.... = 454 g  1 kg = 2.2 lb.... Volume  1 qt = 946 mL  1 L = 1.057 qt  4 qt = 1 gal  1 mL = 1 cm3

  19. MEASUREMENTS - CONVERSIONS 1. The mass of a young student is found to be 87 kg. How many pounds does this mass correspond to? 2. An American visited Austria during the summer summer, and the speedometer in the taxi read 90 km/hr. How fast was the American driving in miles per hour? (Note: 1 mile = 1.6093 km) 3. In most countries, meat is sold in the market by the kilogram. Suppose the price of a certain cut of beef is 1400 pesos/kg, and the exchange rate is 124 pesos to the U.S. dollar. What is the cost of the meat in dollars per pound (lb)? (Note: 1 kg = 2.20 lb)

  20. TEMPERATURE CONVERSIONS • 1. Fahrenheit – at standard atmospheric pressure, the melting point of ice is 32 F, the boiling point of water is 212 F, and the interval between is divided into 180 equal parts. • 2. Celsius – at standard atmospheric pressure, the melting point of ice is 0 C, the boiling point of water is 100 C, and the interval between is divided into 100 equal parts. • 3. Kelvin – assigns a value of zero to the lowest conceivable temperature; there are NO negative numbers. • T(K) = T(C) + 273.15 • T(F) = 1.8T(C) + 32

  21. Introduction to Density • Density is the measurement of the mass of an object per unit volume of that object. d = m / V • Density is usually measured in g/mL or g/cm3 for solids or liquids. • Volume may be measured in the lab using a graduated cylinder or calculated using: Volume = length x width x height if a box or V = pr2h if a cylinder. • Remember 1 mL = 1 cm3

  22. DENSITY DETERMINATION • 1. Mercury is the only metal that is a liquid at 25 C. Given that 1.667 mL of mercury has a mass of 22.60 g at 25 C, calculate its density. • 2. Iridium is a metal with the greatest density, 22.65 g/cm3. What is the volume of 192.2 g of Iridium? • 3. What volume of acetone has the same mass as 10.0 mL of mercury? Take the densities of acetone and mercury to be 0.792 g/cm3 and 13.56 g/cm3, respectively. • 4. Hematite (iron ore) weighing 70.7 g was placed in a flask whose volume was 53.2 mL. The flask was then carefully filled with water and weighed. Hematite and water combined weighed 109.3 g. The density of water is 0.997 g/cm3. What is the density of hematite?

  23. BASIC MATH used in Chemistry 101 The following slides are basic math review. Please look the slides over to refresh your memory. I assume you already know this material and will not cover it in class. Some general math equations: (1) The Generic equation for percent: % = ( portion / total ) 100 (2) The difference/change between two measurements: D X = Xfinal - Xinitial

  24. Mathematical Review Fractions & Decimals • A fraction represents division, the numerator is divided by the denominator. • 2/3 is read as 2 divided by 3 • Proper fraction: numerator is smaller than denominator. Example: 3/5 • Improper fraction: numerator is larger than the denominator. Example: 5/3 • A decimal is a fraction with the division carried out. • A decimal is a fraction expressed in powers of 10. • 0 . 0 0 1 • ones . Tenths hundredths thousandths

  25. Mathematical Review Algebraic Equations • Variables are the symbols used to represent a measurement. • For example; T is the variable for temperature while t is the variable for time. • To isolate one variable of an equation remember to divide if the unwanted variable is on top and to multiply if the variable is on the bottom. An asterisk * represents multiplication. • A = B / C • to isolate C first rearrange the equation to it will read C=? Do this by multiplying both sides by C (since it is on the bottom of a fraction (denominator). • C* A = B *C / C note: C/C = 1 • C * A = B • Now to isolate C we need to divide by A (it is on top of a fraction; A/1 = A) • C * A /A = B /A • Remember: what ever you do to one side you must do it to the other side. • C = B / A

  26. Mathematical Review Algebraic Equations • When multiplication & division is mixed with adding & subtracting, try the multiplication or division first. • (A - D) / (C + F) = B • to solve for C, first rearrange the equation to it will read C=? Do this by multiplying both sides by C + F (since it is on the bottom of a fraction (denominator). • (A - D) * (C + F) / (C + F) = B * (C + F) • (A - D) = B * (C + F) • Now to isolate C we need to divide by B • (A - D) / B = B * (C + F) / B • (A - D) / B = C + F • Now you can subtract F from both sides. • [(A - D) / B] - F = C + F - F • [(A - D) / B] - F = C • which is the same as C = [(A-D) / B] -F If A = 8, D = 2, B = 3, & F = 7 then C must = [(8-2) / 3] - 7 =-5

  27. Mathematical Review Exponents • An exponent is a number written as a superscript. • X2 is X-squared or “X to the power of 2” • The base (X) is multiplied by itself the number of times represented in the exponent(superscript, 2 in this example). • 23 or two cubed (2 is the base and 3 is the exponent) • 23 is 2 * 2 * 2 = 4 * 2 = 8 • A positive exponent represents a large number (greater than one). • 1 x 103 is 10 *10 *10 = 1000 thousand • A negative exponent represents a small number (less than one). • 1 x 10-3 is (1/10) * (1/10) * (1/10) = 0.001 thousandths • When multiplying numbers written with exponents, add the exponents. If dividing then subtract the exponents. • x4 * x6 = x (4+6) = x10 or (2 x 103)(3 x 106) = 6 x 10(3+6) = 6 x 109 • 2x6/7x3 = 0.2857 x(6-3) = 0.2857 x3

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