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BASIC CHEMISTRY CHM 138 CHAPTER 1: UNITS OF MEASUREMENTS.

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Presentation on theme: "BASIC CHEMISTRY CHM 138 CHAPTER 1: UNITS OF MEASUREMENTS."— Presentation transcript:

1 BASIC CHEMISTRY CHM 138 CHAPTER 1: UNITS OF MEASUREMENTS

2 Matter is anything that occupies space and has mass. A substance is a form of matter that has a definite composition and distinct properties. Chemistry is the study of matter and the changes it undergoes liquid nitrogen gold ingots silicon crystals

3 DIMENSIONS Defined as: Any physical quantities that can be measured by measuring devices. There are 2 types of dimension: 1.Basic dimension o The simplest and the most basic physical quantities o There are 7 basic dimensions: - Length (L) - mass (m) - time (t) - temperature (T) - amount of substances (n) - luminous intensity (I) - electrical current

4 2. Derived dimensions o The compound physical quantities that are obtained by combining basic physical by multiplying / dividing the basic dimensions. Derived dimensionsCombination of Basic dimensions AreaLength x length VolumeLength x length x length SpeedLength / time Force(mass x length) / (time x time) DensityMass / (length x length x length) PressureMass / (time x time)

5 International System of Units (SI)

6 S.I system of units Dimension Symbol of dimension Name of unitSymbol of unitDefinition of unit Basic SI Units lengthLmeterm massmkilogramKg timetseconds temperatureTKelvin, degree celciusK, °C Amount of substancenmolemol Derived SI Units EnergyEJouleJ / NmKg.m 2.s -2 ForceFNewtonNKg.m.s -2 PowerPwattW /J/sKg.m 2.s -3 VelocityVMeter per secondm.s -1 AccelerationaMeter per second squaredm.s -2 PressurePNewton per meter squared, Pascal N.m -2 Pa Density ƿ Kilogram per cubic meterKg.m -3

7 American Engineering system of units Dimension Symbol of dimension Name of unitSymbol of unitDefinition of unit Basic SI Units lengthLFeetft massmPound massIbm forceFPound forceIbf timetSecondS temperatureTDegree Rankie, Degree Fahrenheit °R °F Amount of substancenmoleIb mol Derived SI Units EnergyEFoot pound forceFt.Ibf ForceFPound forceIbf PowerPHorsepowerhp VelocityVfeet per secondft.s -1 Accelerationafeet per second squaredft.s -2 PressurePPound force per second inch Psi Density ƿ Pound mass per cubic footIbm.ft -3

8 QuantityEquivalent Values Mass1 kg = 1000 g = metric ton = Ibm = oz 1 Ibm = 16 oz = 5 x ton = g = kg Length1 m = 100 cm = 1000 mm = 10 6 microns (µm) = angstroms (A) = in. = ft = yd = mile 1 ft = 12 in. = 1/3 yd = m = cm Volume1 m 3 = 1000 L = 106 cm 3 = 10 6 mL = ft 3 = imperial gallons = gal = qt 1 ft 3 = 1728 in. 3 = gal = m 3 = L = 28,317 cm 3 Force1 N = 1 kg.m/s 2 = 10 5 dynes = 105 g.cm/s 2 = Ibf 1 Ibf = Ibm.ft/s 2 = N = x 10 5 dynes Pressure1 atm = x 10 5 N/m2 (Pa) = kPa = bar = x 10 6 dynes/cm2 = 760 mm Hg = Ibf/in.2 (psi) = 33.9 ft = in. Hg Energy1 J = 1 N.m = 10 7 ergs = 10 7 dyne.cm = x kW.h = cal = ft-Ibf = x Btu power1 W = 1 J/s = cal/s = ft.Ibf/s = x Btu/s = x hp

9 1 year = 365 days 1 day = 24 hours 1 hour = 60 minutes 1 minute = 60 seconds 30 days = 1 month 1 year = 12 month 1 in = 2.54 cm 1 m = in 1 mile = km 1 mile = 5280 feet 1 mile = 1760 yards 3 feet = 1 yard 12 inches = 1 feet 1 qt = L 1 gal = L 1 L = fl oz 1 fl oz = ml 1 L = qt 1 oz = g 1 lb = g 1 kg = lb 1 g = grains

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11 Matter - anything that occupies space and has mass. mass – measure of the quantity of matter SI unit of mass is the kilogram (kg) 1 kg = 1000 g = 1 x 10 3 g weight – force that gravity exerts on an object A 1 kg bar will weigh 1 kg on earth 0.1 kg on moon weight = c x mass on earth, c = 1.0 on moon, c ~ 0.1 MASS AND WEIGHT

12 Volume – SI derived unit for volume is cubic meter (m 3 ) 1 cm 3 = (1 x m) 3 = 1 x m 3 1 dm 3 = (1 x m) 3 = 1 x m 3 1 L = 1000 mL = 1000 cm 3 = 1 dm 3 1 mL = 1 cm 3 VOLUME

13 Density – SI derived unit for density is kg/m 3 1 g/cm 3 = 1 g/mL = 1000 kg/m 3 density = mass volume d = m V A piece of platinum metal with a density of 21.5 g/cm 3 has a volume of 4.49 cm 3. What is its mass? d = m V m = d x V = 21.5 g/cm 3 x 4.49 cm 3 = 96.5 g DENSITY EXAMPLE:

14 Ex. 1.1

15 Ex. 1.2

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17 K = o C o F = x o C + 32 o F 9 o F 5 o C A Comparison of Temperature Scales Three temperature scales: i) 0 F – degrees Fahrenheit ii) 0 C – degrees Celcius iii)K - Kelvin o C = ( o F – 32 o F) x 5 o C 9 o F

18 Convert F to degrees Celsius. 0 C = x ( 0 F – 32) C = x (172.9 – 32) = Example:

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20 Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000, x The mass of a single carbon atom in grams: x N x 10 n N is a number between 1 and 10 n is a positive or negative integer

21 n > = x 10 2 move decimal left n < = 7.72 x move decimal right Addition or Subtraction 1.Write each quantity with the same exponent n 2.Combine N 1 and N 2 3.The exponent, n, remains the same 4.31 x x 10 3 =4.31 x x 10 4 = 4.70 x 10 4

22 Multiplication 1.Multiply N 1 and N 2 2.Add exponents n 1 and n 2 (4.0 x ) x (7.0 x 10 3 ) = ? = (4.0 x 7.0) x ( ) = 28 x = 2.8 x Division 1.Divide N 1 and N 2 2.Subtract exponents n 1 and n x 10 4 ÷ 5.0 x 10 9 = ? = (8.5 ÷ 5.0) x = 1.7 x (a x 10 m ) x (b x 10 n ) = (axb) x 10 m+n (a x 10 m ) ÷ (b x 10 n ) = (a ÷ b) x 10 m-n

23 Significant Figures - The meaningful digits in a measured or calculated quantity. RULES: Any digit that is not zero is significant kg 4 significant figures Zeros between nonzero digits are significant 606 m 3 significant figures Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure If a number is greater than 1, then all zeros to the right of the decimal point are significant 2.0 mg 2 significant figures

24 If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant g 3 significant figures Numbers that do not contain decimal points, zeros after the last nonzero digit may or may not be significant. 400 cm 1or 2 or 3 significant figures 4 x significant figures 4.0 x significant figures

25 How many significant figures are in each of the following measurements? 24 mL2 significant figures 3001 g 4 significant figures m 3 3 significant figures 6.4 x 10 4 molecules 2 significant figures 560 kg2 significant figures

26 Significant Figures Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers round off to 90.4 one significant figure after decimal point two significant figures after decimal point round off to 0.79

27 Significant Figures Multiplication or Division The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x = = sig figsround to 3 sig figs 6.8 ÷ = sig figsround to 2 sig figs = 0.061

28 Significant Figures Exact Numbers Numbers from definitions or numbers of objects are considered to have an infinite number of significant figures The average of three measured lengths; 6.64, 6.68 and 6.70? = = 6.67 Because 3 is an exact number = 7

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31 Dimensional Analysis Method of Solving Problems 1.Determine which unit conversion factor(s) are needed 2.Carry units through calculation 3.If all units cancel except for the desired unit(s), then the problem was solved correctly. given quantity x conversion factor = desired quantity given unit x = desired unit desired unit given unit

32 Dimensional Analysis Method of Solving Problems Conversion Unit 1 L = 1000 mL 1L 1000 mL 1.63 L x = 1630 mL How many mL are in 1.63 L?

33 The speed of sound in air is about 343 m/s. What is this speed in miles per hour? 1 mi = 1609 m1 min = 60 s1 hour = 60 min 343 m s x 1 mi 1609 m 60 s 1 min x 60 min 1 hour x = 767 mi hour meters to miles seconds to hours conversion units

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