Chemistry The Molecular Nature of Matter and Change
Chemistry The Molecular Nature of Matter and Change Seventh Edition Martin S. Silberberg and Patricia G. Amateis McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Chapter 1: Keys to the Study of Chemistry 1.1 Some Fundamental Definitions
1.2 Chemical Arts and the Origins of Modern Chemistry 1.3 The Scientific Approach: Developing a Model 1.4 Measurement and Chemical Problem Solving 1.5 Uncertainty in Measurement: Significant Figures McGraw-Hill Education. Chemistry Chemistry is the study of matter, its properties, the changes that matter undergoes, and the energy associated with these
changes. McGraw-Hill Education. Definitions Matter: anything that has both mass and volume the stuff of the universe: books, planets, trees, professors, students Composition: the types and amounts of simpler substances that make up a sample of matter
Properties: the characteristics that give each substance a unique identity McGraw-Hill Education. The States of Matter A solid has a fixed shape and volume. Solids may be hard or soft, rigid or flexible. A liquid has a varying shape that conforms to the shape of the container, but a fixed volume. A liquid has an upper surface.
A gas has no fixed shape or volume and therefore does not have a surface. McGraw-Hill Education. The Physical States of Matter Fig 1.1 McGraw-Hill Education.
Physical and Chemical Properties Physical Properties properties a substance shows by itself without interacting with another substance color, melting point, boiling point, density Chemical Properties properties a substance shows as it interacts with, or transforms into, other substances flammability, corrosiveness
McGraw-Hill Education. The Distinction Between Physical and Chemical Change Fig 1.2 McGraw-Hill Education. (A) Paul Morrell/Stone/Getty Images; (B) McGraw-Hill Education/Stephen Frisch,
Sample Problem 1.1 Problem and Plan Visualizing Change on the Atomic Scale PROBLEM: The scenes below represent an atomic-scale view of substance A undergoing two different changes. Decide whether each scene shows a physical or a chemical change. PLAN: We need to determine what change is taking place. The numbers and colors of the little spheres that represent each particle tell its composition. If the composition does not change, the change is physical, whereas a chemical change
results in a change of composition. McGraw-Hill Education. Sample Problem 1.1 Solution SOLUTION: Each particle of substance A is composed of one blue and two red spheres. Sample B is composed of two different types of particles some have two red spheres while some have one red and one blue. As A changes to B, the chemical composition has changed. A B is a chemical
change. McGraw-Hill Education. Sample Problem 1.1 Solution, Contd SOLUTION: Each particle of C is still composed of one blue and two red spheres, but the particles are closer together and are more organized. The composition remains unchanged, but the physical form is different. A C is a physical change.
McGraw-Hill Education. Temperature and Change of State A change of state is a physical change. Physical form changes, composition does not. Changes in physical state are reversible by changing the temperature. A chemical change cannot simply be reversed by a change in
temperature. McGraw-Hill Education. Some Characteristic Properties of Copper Table 1.1 McGraw-Hill Education. (copper) McGraw-Hill Education/Mark Dierker, photographer; (candlestick) Ruth Melnick; (copper carbonate, copper reacting with acid, copper
and ammonia) Sample Problem 1.2 Problem and Plan Distinguishing Between Physical and Chemical Change PROBLEM: Decide whether each of the following processes is primarily a physical or a chemical change, and explain briefly: (a) Frost forms as the temperature drops on a humid winter night. (b) A cornstalk grows from a seed that is watered and fertilized.
(c) A match ignites to form ash and a mixture of gases. (d) Perspiration evaporates when you relax after jogging. (e) A silver fork tarnishes slowly in air. PLAN: Does the substance change composition or just change form? McGraw-Hill Education. Sample Problem 1.2 Solution (a) Frost forms as the temperature drops on a humid winter night physical change
(b) A cornstalk grows from a seed that is watered and fertilized chemical change (c) A match ignites to form ash and a mixture of gases chemical change (d) Perspiration evaporates when you relax after jogging physical change (e) A silver fork tarnishes slowly in air chemical change McGraw-Hill Education.
Energy in Chemistry Energy is the ability to do work. Potential Energy is energy due to the position of an object. Kinetic Energy is energy due to the movement of an object. Total Energy = Potential Energy + Kinetic Energy McGraw-Hill Education. Energy Changes Lower energy states are more stable and are favored over
higher energy states. Energy is neither created nor destroyed it is conserved and can be converted from one form to another McGraw-Hill Education. Potential Energy is Converted to Kinetic Energy A gravitational system. The potential energy gained when a
weight is lifted is converted to kinetic energy as the weight falls. A lower energy state is more stable. Fig 1.3 McGraw-Hill Education. Potential Energy is Converted to Kinetic Energy (2) A system of two balls attached by a spring. The potential
energy gained by a stretched spring is converted to kinetic energy when the moving balls are released. Energy is conserved when it is transformed. Fig 1.3 McGraw-Hill Education. Potential Energy is Converted to Kinetic Energy, Contd
A system of oppositely charged particles. The potential energy gained when the charges are separated is converted to kinetic energy as the attraction pulls these charges together. Fig 1.3 McGraw-Hill Education. Potential Energy is Converted to Kinetic Energy, Further Contd A system of fuel and exhaust. A fuel is higher in chemical
potential energy than the exhaust. As the fuel burns, some of its potential energy is converted to the kinetic energy of the moving car. Fig 1.3 McGraw-Hill Education. Chemical Arts and the Origins of Modern Chemistry Alchemy, medicine, and technology placed little emphasis on
objective experimentation, focusing instead on mystical explanations or practical experience, but these traditions contributed some apparatus and methods that are still important. Lavoisier overthrew the phlogiston theory by showing, through quantitative, reproducible measurements, that oxygen, a component of air, is required for combustion and combines with a burning substance. McGraw-Hill Education.
The Scientific Approach to Understanding Nature Fig 1.6 McGraw-Hill Education. SI Base Units Table 1.2
McGraw-Hill Education. Common Decimal Prefixes Used With SI Units Table 1.3 McGraw-Hill Education. Common SI-English Equivalent Quantities Table 1.4
McGraw-Hill Education. Some Volume Relationships in SI Fig 1.7 McGraw-Hill Education. Common Laboratory Volumetric Glassware Fig 1.8
McGraw-Hill Education. Quantities of Length (A), Volume (B), and Mass (C) Fig 1.9 McGraw-Hill Education. Chemical Problem Solving All measured quantities consist of
a number and a unit. Units are manipulated like numbers: McGraw-Hill Education. Conversion Factors A conversion factor is a ratio of equivalent quantities used to express a quantity in different units. The relationship 1 mi = 5280 ft gives us the conversion factor:
McGraw-Hill Education. Conversion Factor Problem A conversion factor is chosen and set up so that all units cancel except those required for the answer. PROBLEM: The height of the Angel Falls is 3212 ft. Express this quantity in miles (mi) if 1 mi = 5280 ft. PLAN: Set up the conversion factor so that ft will cancel and the answer will be in mi.
SOLUTION: McGraw-Hill Education. Systematic Approach to Solving Chemistry Problems State Problem
Plan Clarify the known and unknown. Suggest steps from known to unknown. Prepare a visual summary of steps that includes conversion factors, equations, known variables. Solution Check
Comment Follow-up Problem McGraw-Hill Education. Sample Problem 1.3 Problem and Plan Converting Units of Length PROBLEM: To wire your stereo equipment, you need 325 centimeters (cm) of speaker wire that sells for $0.15/ft. What is the
price of the wire? PLAN: We know the length (in cm) of wire and cost per length ($/ft). We have to convert cm to inches and inches to feet. Then we can find the cost for the length in feet. McGraw-Hill Education. Sample Problem 1.3 - Solution
SOLUTION: Length (in) = length (cm) x conversion factor Length (ft) = length (in) x conversion factor Price ($) = length (ft) x conversion factor McGraw-Hill Education. Sample Problem 1.4 Problem and Plan Converting Units of Volume PROBLEM: A graduated cylinder
contains 19.9 mL of water. When a small piece of galena, an ore of lead, is added, it sinks and the volume increases to 24.5 mL. What is the volume of the piece of galena in cm3 and in L? PLAN: The volume of the galena is equal to the difference in the volume of the water before and after the addition.
McGraw-Hill Education. Sample Problem 1.4 - Solution SOLUTION McGraw-Hill Education. Sample Problem 1.5 Problem and Plan Converting Units of Mass
PROBLEM: Many international computer communications are carried out by optical fibers in cables laid along the ocean floor. If one strand of optical fiber weighs 1.19 x 10-3 lb/m, what is the mass (in kg) of a cable made of six strands of optical fiber, each long enough to link New York and Paris (a distance of 8.94 x 103 km)?
PLAN: The sequence of steps may vary but essentially we need to find the length of the entire cable and convert it to mass. McGraw-Hill Education. Sample Problem 1.5 - Solution SOLUTION:
McGraw-Hill Education. Sample Problem 1.6 Problem and Plan Converting Units Raised to a Power PROBLEM: A furniture factory needs 31.5 ft2 of fabric to upholster one chair. Its Dutch supplier sends the fabric in bolts that hold exactly 200 m2. How many chairs can be upholstered with three bolts of fabric?
PLAN: We know the amount of fabric in one bolt in m2; multiplying the m2 of fabric by the number of bolts gives the total amount of fabric available in m2. We convert the amount of fabric from m2 to ft2 and use the conversion factor 31.5 ft2 of fabric = 1 chair to find the number of chairs (see the road map). McGraw-Hill Education.
Sample Problem 1.6 - Solution SOLUTION: Converting from number of bolts to amount of fabric in m2: Converting the amount of fabric from m2 to ft2: Since 0.3048 m = 1 ft, we have (0.3048)2 m2 = (1)2 ft2, so Finding the number of chairs: McGraw-Hill Education. Density
At a given temperature and pressure, the density of a substance is a characteristic physical property and has a specific value. McGraw-Hill Education. Densities of Some Common Substances McGraw-Hill Education.
Sample Problem 1.7 Problem and Plan Calculating Density from Mass and Volume PROBLEM: Lithium, a soft, gray solid with the lowest density of any metal, is a key component of advanced batteries. A slab of lithium weighs 1.49 x 103 mg and has sides that are 20.9 mm by 11.1 mm by 11.9 mm. Find the density of lithium in g/cm3. PLAN: Density is expressed in g/cm3 so we need the mass in g and the volume in cm3.
McGraw-Hill Education. Sample Problem 1.7 Plan, Contd McGraw-Hill Education. Sample Problem 1.7 - Solution SOLUTION:
Similarly the other sides will be 1.11 cm and 1.19 cm, respectively. McGraw-Hill Education. Some Interesting Temperatures Fig 1.10 McGraw-Hill Education.
Freezing and Boiling Points of Water Fig 1.11 McGraw-Hill Education. Temperature Scales Kelvin (K) The absolute temperature scale begins at absolute zero and has only positive values. Note that the kelvin is not used with the degree sign (o). Celsius (oC) The Celsius scale is based on the freezing and
boiling points of water. This is the temperature scale used most commonly around the world. The Celsius and Kelvin scales use the same size degree although their starting points differ. Fahrenheit (oF) The Fahrenheit scale is commonly used in the U.S. The Fahrenheit scale has a different degree size and different zero points than both the Celsius and Kelvin scales. McGraw-Hill Education.
Temperature Conversions McGraw-Hill Education. Sample Problem 1.8 Problem, Plan and Solution Converting Units of Temperature
PROBLEM: A child has a body temperature of 38.7C, and normal body temperature is 98.6F. Does the child have a fever? What is the childs temperature in kelvins? PLAN: We have to convert C to F to find out if the child has a fever. We can then use the C to Kelvin relationship to find the temperature in Kelvin. SOLUTION: Converting from C to F Yes, the child has a fever.
Converting from C to K McGraw-Hill Education. Extensive and Intensive Properties Extensive properties are dependent on the amount of substance present; mass and volume, for example, are extensive properties. Intensive properties are independent of the amount of substance; density is an intensive property.
McGraw-Hill Education. Significant Figures Every measurement includes some uncertainty. The rightmost digit of any quantity is always estimated. The recorded digits, both certain and uncertain, are called significant figures. The greater the number of significant figures in a quantity, the greater its certainty.
McGraw-Hill Education. The Number of Significant Figures in a Measurement Fig 1.13 McGraw-Hill Education. Determining Which Digits Are Significant All digits are significant
except zeros that are used only to position the decimal point. Zeros that end a number are significant whether they occur before or after the decimal point as long as a decimal point is present. 1.030 mL has 4 significant figures. 5300. L has 4 significant figures. If no decimal point is present zeros at the end of the number are not significant.
5300 L has only 2 significant figures. McGraw-Hill Education. Sample Problem 1.9 Problem and Plan Determining the Number of Significant Figures PROBLEM: For each of the following quantities, underline the zeros that are significant figures (sf), and determine the number of significant figures in each quantity. For (d) to (f), express each in exponential notation first.
(a) 0.0030L (b) 0.1044g (d) 0.00004715m (e) 57,600.s (c) 53.069L (f) 0.0000007160cm3 PLAN: We determine the number of significant figures by
counting digits, paying particular attention to the position of zeros in relation to the decimal point, and underline zeros that are significant. McGraw-Hill Education. Sample Problem 1.9 - Solution SOLUTION: (a) 0.0030 L has 2 sf (b) 0.1044 g has 4 sf
(c) 53,069 mL has 5 sf (d) 0.00004715 m = 4.715 x 10-5 m has 4 sf (e) 57,600. s = 5.7600 x 104 s has 5 sf (f) 0.0000007160 cm3 = 7.160 x 10-7 cm3 has 4 sf McGraw-Hill Education. Rules for Significant Figures in Calculations 1. For multiplication and division. The answer contains the same number of significant figures as there are in the
measurement with the fewest significant figures. Multiply the following numbers: McGraw-Hill Education. Rules for Significant Figures in Calculations, Contd 2. For addition and subtraction. The answer has the same number of decimal places as there are in the measurement with the fewest decimal places.
Example: adding two volumes Example: subtracting two volumes McGraw-Hill Education. Rules for Rounding Off Numbers 1. If the digit removed is more than 5, the preceding number increases by 1. 5.379 rounds to 5.38 if 3 significant figures are retained.
2. If the digit removed is less than 5, the preceding number is unchanged. 0.2413 rounds to 0.241 if 3 significant figures are retained. 3. If the digit removed is 5 followed by zeros or with no following digits, the preceding number increases by 1 if it is odd and remains unchanged if it is even. 17.75 rounds to 17.8, but 17.65 rounds to 17.6. If the 5 is followed by other nonzero digits, rule 1 is followed:
17.6500 rounds to 17.6, but 17.6513 rounds to 17.7 McGraw-Hill Education. Rules for Rounding Off Numbers, Contd 4. Be sure to carry two or more additional significant figures through a multistep calculation and round off the final answer only. McGraw-Hill Education.
Significant Figures in the Lab The measuring device used determines the number of significant digits possible. Fig 1.14 McGraw-Hill Education. Exact Numbers Exact numbers have no uncertainty associated with them. Numbers may be exact by definition:
1000 mg= 1 g 60 min = 1 hr 2.54 cm = 1 in Numbers may be exact by count: exactly 26 letters in the alphabet Exact numbers do not limit the number of significant digits in a calculation.
McGraw-Hill Education. Sample Problem 1.10 Problem and Plan Significant Figures and Rounding PROBLEM: Perform the following calculations and round each answer to the correct number of significant figures:
PLAN: We use the rules for rounding presented in the text: (a) We subtract before we divide. (b) We note that the unit conversion involves an exact number. McGraw-Hill Education. Sample Problem 1.10 - Solution SOLUTION: McGraw-Hill Education.
Precision, Accuracy, and Error Precision refers to how close the measurements in a series are to each other. Accuracy refers to how close each measurement is to the actual value. Systematic error produces values that are either all higher or all lower than the actual value. This error is part of the experimental system.
Random error produces values that are both higher and lower than the actual value. McGraw-Hill Education.
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