Chemistry 103 Lecture 3. Outline I. Mathematics of Chemistry –Dimensional Analysis –Density...
-
date post
20-Dec-2015 -
Category
Documents
-
view
224 -
download
4
Transcript of Chemistry 103 Lecture 3. Outline I. Mathematics of Chemistry –Dimensional Analysis –Density...
Chemistry 103Lecture 3
Outline
I. Mathematics of Chemistry– Dimensional Analysis– Density– Temperature Scales
II. Matter Classified
Math Operations
• Calculate each to the correct number of sig figs.
• 32.145 cm x 17.8 cm x 25 cm =
• 1450.0 kg + 250 kg + 1.235 kg =
Dimensional Analysis
Review
Dimensional Analysis
• A problem solving method in which the units (associated with numbers) are used as a guide in setting up the calculations.
unitsdesiredinAnswerunitgiven
unitdesiredxunitgivenintMeasuremen
Conversion Factor
Dimensional Analysis
How many seconds are in 2 minutes?
2 minutes x 60 seconds =
1 minute
120 seconds (exactly)
Learning Check
• If a bucket contains 4.65L of water. How many gallons of water is this?
(1 gallon = 4qts, 1L = 1.057qt)
A. 1.23 gallons
B. 4.92 gallons
C. 17.6 gallons
Dimensional Analysis
If Jules Vern expressed the title of his famous book, “Twenty Thousand Leagues Under the Sea” in feet, what would the title be?
(1mile = 5280ft, 1 League = 3.450miles)
Practice Problem
• During surgery, a patient received 5.0 pints of plasma. How many mL of plasma is this? (1L = 1.057qts, 2 pints = 1qt)
A. 2400mL
B. 2.4mL
C.4700mL
D.4.7mL
Dimensional Analysis
If a particular fad diet claims a weight loss of 3.0 pounds per week, how many grams per day would this be? (1lb = 453.6g)
A. 1400 g/day
B. 0.046g/day
C. 190 g/day
Converting from squared units to squared units or cubed units to cubed units
• Warning: This type of conversion gives many students difficulties!!!!!
• The one thing you have to remember:– What does it mean to say that a unit is squared or
cubed?– m2 = m x m; s3 = s x s x s
• When there are squared or cubed units, you have multiple units to cancel out!
Examples
• Convert 127.4 cm3 to m3.
(100cm = 1m)
• Convert .572 miles2 to km2.
(1km = .621miles)
Percent Factor in a ProblemIf the thickness of the skin fold at the waist indicates an 11% body fat, how much fat is in a person with a mass of 86 kg?
percent factor
86 kg mass x 11 kg fat
100 kg mass
= 9.5 kg fat
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Even MORE Practice with Conversion Factors
• A lean hamburger is 22% fat by weight. How many grams of fat are in 0.25 lb of the hamburger?
Density
• A ratio of the mass of an object divided by its volume
Density = Mass/Volume
• Typical units = g/mL (NOTE: 1mL=1cm3)
Measuring Density in Lab
Measuring Density in Lab
68.60g = 68.60g(45.0mL - 35.5mL) 9.5mL
Measuring Density in Lab
68.60g = 68.60g = 7.2g/mL(45.0mL - 35.5mL) 9.5mL
Densities of Common Substances
Sink or Float• Ice floats in water
because the density of ice is less than the density of water.
• Aluminum sinks because its density is greater than the density of water.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Sink or Float• Ice floats in water
because the density of ice is less than the density of water.
• Aluminum sinks because its density is greater than the density of water.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Which diagram correctly represents the liquid layers in the cylinder? Karo (K) syrup (1.4 g/mL), vegetable (V) oil (0.91 g/mL,) water (W) (1.0 g/mL)
A B C
K
K
W
W
W
V
V
V
K
Learning Check
A)
Vegetable oil 0.91 g/mL
Water 1.0 g/mL
Karo syrup 1.4 g/mL
K
W
V
Solution
Osmium is a very dense metal. What is its density in g/cm3 if 50.0 g of osmium has a volume of 2.22 cm3?
a) 2.25 g/cm3
b) 22.5 g/cm3
c) 111 g/cm3
Learning Check
Osmium is a very dense metal. What is its density in g/cm3 if 50.0 g of osmium has a volume of 2.22 cm3?
a) 2.25 g/cm3
b) 22.5 g/cm3
c) 111 g/cm3
50.0g = 22.5g/cm3
2.22cm3
Learning Check
Density can be written as an equality. • For a substance with a density of 3.8 g/mL, the equality is:
3.8 g = 1 mL
• From this equality, two conversion factors can be written for density.
Conversion 3.8 g and 1 mL factors 1 mL 3.8 g
Density as a Conversion Factor
DENSITY PRACTICE
The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane?
A) 0.614 kg
B) 614 kg
C) 1.25 kg
Learning Check
Density Example
• You have been given 150g of ethyl alcohol which has a density of 0.785g/mL. Will this quantity fit into a 150mL beaker?
A. YES B. NO
A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 lb aluminum, how many liters of aluminum (D=2.70 g/cm3) are obtained from the cans?
A) 1.0 L B) 2.0 L C) 4.0 L
Learning Check
31
Temperature
Temperature
• Is a measure of how hot or cold an object is compared to another object
• Indicates that heat flows from the object with a higher temperature to the object with a lower temperature
• Is measured using a thermometer
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Temperature Scales
Solving a Temperature Problem
A person with hypothermia has abody temperature of 34.8°C. What isthat temperature in °F?
TF = 1.8 TC + 32
TF = 1.8 (34.8°C) + 32° exact tenths exact
= 62.6 + 32° = 94.6°F tenths Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Converting between Temperature Scales
• ***Conversions between Celsius and Kelvin– (Temperature in K) = (temperature in oC) + 273
– (temperature in oC) = (temperature in K) – 273
• Conversions between Celsius and Fahrenheit– oF = 9/5 (oC) + 32
– oC = 5/9(oF – 32)
Chemistry is the study of Matter
Matter is anything that has mass and
takes up space.
Chemistry is the study of Matter
Matter has both physical and
chemical properties
Physical Properties
Physical properties are:
• Characteristics observed or measured without changing the identify of a substance.
• Shape, physical state, odor, boiling and freezing points, density, and color of that substance. (Changes of state)
Chemical Properties
Chemical properties describe the ability of a substance
• To interact with other substances• To change into a new substance
Example:
Oxygen reacts with methane
Gas to form carbon dioxide & water
Matter Classified
Matter
Pure Substance Mixture
Matter Classified
Matter
Pure Substance Mixture
Classification of Matter
• Pure Substances: A form of matter that always has a definite and constant composition. Properties always the same under a given set of conditions (temperature & pressure)
Matter
Pure Substance Mixture
Element Compound
Pure Substances: Elements
• Element – Pure substance that can not be broken down into simpler
substances by chemical means.
Copper (Cu)Lead (Pb)Aluminum (Al)
– The most basic form of matter.– Each element can be found on the periodic table.
Periodic Table of Elements
Names and Symbols of the Elements
• Each element has a unique name and is represented by a unique symbol
– Chemical symbol: a one- or two-letter designation for an element derived from the element’s name
– First letter of the symbol is always capitalized
Several symbols are derived from Latin names as shownbelow:
Cu, copper (cuprum) Au, gold (aurum)
Fe, iron (ferrum) Ag, silver (argentum)
Symbols from Latin Names
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Select the correct symbol for each:1. Calcium
A) C B) Ca C) CA
2. Sulfur A) S B) Sl C) Su
3. Iron A) Ir B) FE C) Fe
Learning Check
Select the correct symbol for each:
1. Calcium B) Ca
2. Sulfur A) S
3. Iron C) Fe
Learning Check
Select the correct name for each symbol:1. N
A) neon B) nitrogen C) nickel
2. P A) potassium B) phlogiston C) phosphorus
3. Ag A) silver B) agean C) gold
Learning Check
Select the correct name for each symbol:1. N
A) neon B) nitrogen C) nickel
2. P A) potassium B) phlogiston C) phosphorus
3. Ag A) silver B) agean C) gold
Learning Check