Temperature and Density

Temperature and Density Chapter 2.9/3.10

Anders Celsius 1701-1744 Lord Kelvin (William Thomson) 1824-1907 Temperature Scales • Fahrenheit • Celsius • Kelvin

212 ˚F 100 ˚C 373 K 32 ˚F 0 ˚C 273 K Temperature Scales Fahrenheit Celsius Kelvin Boiling point of water Freezing point of water

Calculations Using Temperature • Generally require temp’s in kelvins • T (K) = t (˚C) + 273.15 • t (˚C) = T (K) - 273.15 • Body temp = 37 ˚C + 273 = 310 K • Liquid nitrogen = -196 ˚C + 273 = 77 K

Fahrenheit Formula Zero point: 0°C = 32°F °F = 9/5 °C + 32

Celsius Formula °C = (°F – 32) * 5/9

Temperature Conversions A person with hypothermia has a body temperature of 29.1°C. What is the body temperature in °F? °F = 9/5 (29.1°C) + 32 = 52.4 + 32 = 84.4°F

Learning Check The normal temperature of a chickadee is 105.8°F. What is that temperature in °C? 1) 73.8 °C 2) 58.80 °C 3) 41.00 °C 4) 41.0 °C

Learning Check Pizza is baked at 455°F. What is that in °C? 1) 437 °C 2) 235°C 3) 221°C

Platinum Mercury Aluminum DENSITY - an important and useful physical property 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

DENSITY • Intensive Property: depends only on the composition of substance not size. • Density generally decreases as temperature increases • Units = g/cm3 or g/mL

ProblemA piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).

Strategy 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density.

SOLUTION 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density. (9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3 Note only 2 significant figures in the answer!

PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?

PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg? Strategy 1. Use density to calc. mass (g) from volume. 2. Convert mass (g) to mass (lb) Need to know conversion factor = 454 g / 1 lb First, note that1 cm3 = 1 mL

PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg? 1. Convert volume to mass 2. Convert mass (g) to mass (lb)

Learning Check Osmium is a very dense metal. What is its density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22cm3? 1) 2.25 g/cm3 2) 22.5 g/cm3 3) 111 g/cm3

Solution 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = 50.00 g = volume 2.22 cm3 = 22.522522 g/cm3 =22.5 g/cm3

Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL

Learning Check What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm3 2) 6.0 g/m3 3) 252 g/cm3 33 mL 25 mL

The Density of Water • The density of water is 1 g/mL • Anything that sinks in water has a higher density and anything that floats has a lower density

Learning Check Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) K W V V K W W V K

Learning Check The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane? 1) 0.614 kg 2) 614 kg 3) 1.25 kg

Learning Check If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given? 1) 0.548 L 2) 1.25 L 3) 1.83 L

Learning Check A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 pound of aluminum, how many liters of aluminum (D=2.70 g/cm3) are obtained from the cans? 1) 1.0 L 2) 2.0 L 3) 4.0 L

Temperature and Density