userdata-paziras-Chem101-Chap_01B

Measurementoftemperature

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: lways think : ­ Which unit is larger ? (m) ­ Which unit is smaller ? (mm) 6 1m = 10 mm 1 mm ¾¾¾¾> IS CORRECT = 1 x 10 6 m ¾¾¾¾> IS Also Correct 18 Chemistry 101 Chapter 1 I. BASE UNITS 1.Measurement of Length Base unit: The meter = m Also commonly used in chemistry: cm, mm, mm, nm, pm (for atomic sizes) 1 m 1 m 1 m 1 m 1 m = = = = = 2 10 cm 3 10 mm 6 10 mm 9 10 nm 12 10 pm 10-2 m 10-3 m 10-6 m 10-9 m 10-12 m OR OR OR OR OR 1 cm 1 mm 1 mm 1 nm 1 pm = = = = = OR 1 A = 10-10 m Also used: the Angstrom, A 1 m = 10 10 A · NOTE : The Angstrom IS NOT AN SI UNIT 2. Measurement of Mass Base Unit: the kilogram, kg (the gram would not be practical since it is too small) 3. Measurement of Time Base Unit: the second, s · Conversion to minutes (60 sec/min) or hours (60 min/hr) is an exception to the decimal­based prefixes of the SI (is due to the calendar) · Recently, nanoseconds (10-9 s) and picoseconds (10-12 s) are increasingly used in computer work 19 Chemistry 101 Chapter 1 4. Measurement of Temperature · Temperature is a measure of how hot or cold a substance is. · It is a quantity that determines the direction of heat flow: warmer ® cooler · Three temperature scales are commonly used: Celsius, Kelvin (absolute) and Fahrenheit · To convert between Fahrenheit and Celsius; REMEMBER: 1.8 unit F = 1 unit C 32 oF = 0 oC o o o F = 32 + (1.8 x C) or o C = F ­ 32 1.8 · To convert between Celsius and Kelvin: REMEMBER: ­The Kelvin temperature is 273 degrees higher than the Celsius K = o C + 273 o C = K ­ 273 20 Chemistry 101 Chapter 1 II. DERIVED UNITS 1. Volume Base Unit : Commonly used: 3 m 3 dm Not practical because it is very large Also called “THE LITER (L)” 1 dm = 10 cm 3 3 1 dm = 1 L 1 cm = 1mL NOTE: 3 1 dm 1 L 3 = (10 cm)3 = 1,000 cm = 1,000 mL IMPORTANT RELATIONSHIPS TO REMEMBER: 3 1 dm = 1 L 3 1 cm = 1 mL 3 3 1 dm = 1000 cm 1 L = 1000 mL 3 3 1 cm = 0.001 dm 1 mL = 0.001 L 2. Density (d): Density is the mass of a unit volume d = m ass m = volu m e V 21 Chemistry 101 Chapter 1 Examples: 1. Calculate the density of a piece of glass with a mass of 6.65 g and a volume of 2.95 mL. m = 6.65 g V = 2.95 mL d =? 2. Calculate the thickness of an Aluminum foil 15.38 cm long and 14.39 cm wide. The mass of 3 the foil is 1.4939 g. The density of aluminum is 2.70 g/cm . (HINT: We consider the Aluminum foil to be a rectangular solid). L = 15.38 cm W = 14.39 cm m = 1.4939 g 3 d = 2.70 g/cm Thickness = Height = ? d = m m = V L x W x Th Solve the equation for the unknown (Th), before using numbers: Th = m 1.4939 g = = 2.50 x 10­3 cm 3 d x L x W (2.70 g/cm )(15.38 cm)(14.39 cm) Notes: · The units cancel out. The units obtained for the answer are cm, which is to be expected. · If the units would not be units of length, that would imply that you made a mistake in your algebra (when you solved for the unknown) 22 Chemistry 101 Chapter 1 DIMENSIONAL ANALYSIS (FACTOR­LABEL METHOD) · It is a method...
View Full Document

Ask a homework question - tutors are online