Lesson 1: What Is Chemistry? PDF

Lesson 1 What is Chemistry?  Focus Question How can chemistry help you understand the world?  New Vocabulary chemistry applied research science mass hypothesis weight theory substance scientific law...

Lesson 1 What is Chemistry?  Focus Question How can chemistry help you understand the world?  New Vocabulary chemistry applied research science mass hypothesis weight theory substance scientific law model pure research  Review Vocabulary matter: anything that has mass and takes up space  Why study chemistry? Chemistry is the study of matter and the changes that it undergoes. Everything in the universe is composed of matter, including particles in space, in the air, and in all the things around you. Matter Not Matter Stars Space Books Light People Thoughts Air Radio waves  Chemistry: The Central Science Science is the use of evidence to construct testable explanations and predictions. Science is also the knowledge gained from this process. A basic understanding of chemistry is central to all sciences. Chemists help solve many of the problems and issues that we face today. Chemistry: The Central Science Some Branches of Chemistry  Theory and Scientific Law A testable explanation of a situation or phenomena is called a hypothesis. A theory is an explanation that has been repeatedly supported by many experiments. A theory states a broad principle of nature that has been supported over time by repeated testing. Theories are successful if they can be used to make predictions that are true. A scientific law is a relationship in nature that is supported by many experiments, and no exceptions to these relationships are found.  Types of Scientific Investigations Pure research is research to gain knowledge for the sake of knowledge itself. For example, the study of carbon molecules in space led to the discovery of buckminsterfullerenes. Applied research is research undertaken to solve a specific problem. For example, scientists have developed ways to use buckminsterfullerenes to fight cancer.  Matter and Its Characteristics Mass is a measurement that reflects the amount of matter. Weight is a measurement of Earth’s gravitational pull on matter. A substance, also called a chemical, is matter that has a definite and uniform composition. Chemistry uses models of matter at the submicroscopic or atomic scale to explain the behavior of matter at the macroscopic scale. Physical models show how parts relate to one another. They can also be used to show how things appear when they change position or how they react when outside forces act on them. Examples include a model of the solar system, a globe of the Earth, or a model of the human torso.  Quiz 1. What is the study of matter and the changes it undergoes? A science B chemistry CORRECT C pure research D applied research  Quiz 2. In science, theory is closest in meaning to A guess C explanation CORRECT B hypothesis D study  Quiz 3. Why is chemistry sometimes called the central science? A Chemistry studies the center of atoms. B Chemistry has many different branches. C Chemistry is important to many other sciences. CORRECT D Chemistry is studied in between biology and physics.  Quiz 4. Which of these is another word for substance? A mass B weight C chemical CORRECT D matter  Quiz 5. Suppose a scientist is working to develop a new waterproof, breathable fabric for hiking boots. This is an example of ______. A biochemistry C pure research B theoretical chemistry D applied research CORRECT  Lesson 2 Measurement  Focus Question Why do scientists use standardized units?  New Vocabulary base unit liter second density meter scientific notation kilogram dimensional analysis kelvin conversion factor derived unit  Review Vocabulary mass: a measurement that reflects the amount of matter an object contains  Units Système Internationale d'Unités SI Base Units (SI) is an internationally agreed- upon system of measurements. There are seven base units in SI. A base unit is a defined unit in a system of measurement that is based on an object or event in the physical world.  Base Units and SI Prefixes To better describe the range of possible measurements, scientists add prefixes to the base units. These prefixes are based on factors of ten. SI Prefixes Why are prefixes often added to SI units? For example, g/cm3 is an SI unit of density, where cm3 is to be interpreted as (cm)3. Prefixes are added to unit names to produce multiples and submultiples of the original unit. of the original unit. How to Convert Kilo to Deci 1 k = 10000 d 1 d = 0.0001 k Example: convert 15 k to d 15 k = 15 × 10000 d = 150000 d H.w 1. convert 13 centi to kilo 2. convert 25 mega to milli Q/ how to convert mega micro and nano to meter ? note: 1 megameter = 1000000 m 1 micrometer = 0.000001 m 1 nano meter = 0.000000001 m Example : 1. Convert 15 mm to m 2. Convert 5000000 um to m 3. Convert 1000000 nm to m  Base Units and SI Prefixes The SI base unit of time is the second (s), which is based on the frequency of radiation given off by a cesium-133 atom. The SI base unit of length is the meter (m), which is the distance light travels in a vacuum in 1/299,792,458th of a second. The SI base unit of mass is the kilogram (kg), which is about 2.2 pounds.  Base Units and SI Prefixes The SI base unit of temperature is the kelvin (K). Zero kelvin is the point at which there is virtually no particle motion or kinetic energy. It is also known as absolute zero. Two other temperature scales are Fahrenheit and Celsius. To convert between degrees Fahrenheit and degrees Celsius, use this equation: °F = 1.8(°C) + 32 -Absolute zero is the lowest temperature possible. At a temperature of absolute zero there is no motion and no heat. Absolute zero occurs at a temperature of 0 kelvin, or -273.15 degrees Celsius, or at -460 degrees Fahrenheit.  °F = 1.8(°C) + 32 -imagine a friend from Canada calls you and say that it is 35 °C outside what is the temperature in degrees Fahrenheit ? To convert to degrees Fahrenheit substitute 35 °C into the above equation and solve. -if it is 35 °F outside , what is the temperature in degrees Celsius? H.W / which is warmer 25 °F or 25 °C ?  Base Units and SI Prefixes The Celsius and Kelvin temperature scales are closely related. A difference of one degree Celsius equals a difference of one kelvin. To convert from degrees Celsius to kelvins, use this equation: K = °C + 273  Example: 0°C = 0 + 273.15 = 273.15 K Example 1: Convert 25.0 °C to Kelvin. 25.0 + 273 = 298 K Example 2: Convert 375 K to degrees Celsius. 375 − 273 = 102 °C Example 3: Convert −50 °C to Kelvin. −50 + 273 = 223 K Example 1:convert 300 k to °C Example 2: convert 250 k to °C Example 3: convert 155 k to °C  Derived Units Not all quantities can be measured with SI base units. A unit that is defined by a combination of base units is called a derived unit. Example: The SI unit for speed is meters per second (m/s).  Derived Units Volume is measured in derived units. The SI unit of volume is cubic meters (m3), which is actually very large. A more common unit of volume is the liter (L), which equals 1 cubic decimeter (dm3). Units of milliliters (mL) or cubic centimeters (cm3) are often used for smaller volumes. 1 mL = 1 cm3 1 L = 1000 mL  Derived Units These cubes show the relationships between cubic meters (m3), cubic decimeters (dm3), cubic centimeters (cm3), and cubic millimeters (mm3).  Derived Units Density is a physical property of matter defined as the amount of mass per unit volume. Density uses derived units of g/cm3 for solids and g/mL for liquids and gases. The density of a substance usually cannot be measured directly. You can calculate density using this equation: USING DENSITY AND VOLUME TO FIND MASS KNOWN UNKNOWN density = 2.7 g/mL mass = ? g Use with Example Problem 1. initial volume = 10.5 mL Problem final volume = 13.5 mL When a piece of aluminum is placed in a 25-mL graduated cylinder that contains 10.5 SOLVE FOR THE UNKNOWN mL of water, the water level rises to 13.5 mL. What is the mass of the aluminum? State the equation for volume. volume of sample = final volume - initial Response volume ANALYZE THE PROBLEM Substitute final volume = 13.5 mL and The mass of aluminum is unknown. The known initial volume = 10.5 mL. values include the initial and final volumes and volume of sample = 13.5 mL - 10.5 mL the density of aluminum. The volume of the sample equals the volume of water displaced in volume of sample = 3.0 mL the graduated cylinder. The density of aluminum State the equation for density. is 2.7 g/mL. Use the density equation to solve for the mass of the aluminum sample. USING DENSITY AND VOLUME TO FIND MASS SOLVE FOR THE UNKNOWN EVALUATE THE ANSWER Solve the equation for mass. Check your answer by using it to calculate the mass = volume × density density of aluminum. Substitute volume = 3.0 mL and density = 2.7 g/mL. mass = 3.0 mL × 2.7 g/mL Because the calculated density for aluminum Multiply, and cancel units. is correct, the mass value must also be correct. mass = 3.0 mL × 2.7 g/mL = 8.1 g Q/ 116 g of sunflower oil is used in a recipe. The density of the oil is 0.925 g/ml. What is the volume of the sunflower oil in ml?  Scientific Notation Scientific notation can be used to express any number as a number between 1 and 10 (the coefficient) multiplied by 10 raised to a power (the exponent). Carbon atoms in the Hope Diamond = 4.6 x 1023 4.6 is the coefficient and 23 is the exponent. Count the number of places the decimal point must be moved to give a coefficient between 1 and 10. The number of places moved equals the value of the exponent. The exponent is positive when the decimal moves to the left and negative when the decimal moves to the right. SCIENTIFIC NOTATION SOLVE FOR THE UNKNOWN Use with Example Problem 2. Move the decimal point to give a coefficient Problem between 1 and 10. Count the number of Write the following data in scientific places the decimal point moves, and note the notation. direction. Move the decimal point six places to the a. The diameter of the Sun is 1,392,000 km. left. b. The density of the Sun’s lower atmosphere is 0.000000028 g/cm3. Move the decimal point eight places to the right. Response ANALYZE THE PROBLEM Write the coefficients, and multiply them You are given two values, one much larger than 1 by 10n where n equals the number of and the other much smaller than 1. In both cases, places moved. When the decimal point the answers will have a coefficient between 1 and moves to the left, n is positive; when the 10 multiplied by a power of 10. decimal point moves to the right, n is negative. Add units to the answers. a. 1.392 × 106 km b. 2.8 × 10-8 g/cm3 SCIENTIFIC NOTATION EVALUATE THE ANSWER The answers are correctly written as a coefficient between 1 and 10 multiplied by a power of 10. Because the diameter of the Sun is a number greater than 1, its exponent is positive. Because the density of the Sun’s lower atmosphere is a number less than 1, its exponent is negative. Q/ express each number in scientific notation a/ 700 e/0.0054 b/38000 f/0.00000687 c/ 4500000 g/0.000000076 d/685000000000 h/0.0000000008  Addition and Subtraction in Scientific Notation For adding and subtracting numbers in scientific notation, the exponents must be the same. Example: 2.840 x 1018 + 3.60 x 1017 = ? How would you rewrite one of these numbers so their exponents are the same? Remember that moving the decimal to the right or left changes the exponent. 2.840 x 1018 + 0.360 x 1018 = ? Now you can add or subtract the coefficients. 2.840 x 1018 + 0.360 x 1018 = 3.200 x 1018  Multiplication and Division in Scientific Notation To multiply numbers in scientific notation, multiply the coefficients, then add the exponents. Example: (4.6 x 1023)(2.0 x 10-23) = 9.2 x 100 = 9.2 To divide numbers in scientific notation, divide the coefficients, then subtract the exponent of the divisor from the exponent of the dividend. Example: (9 x 107) ÷ (3 x 10-3) = 3 x 1010 MULTIPLYING AND DIVIDING NUMBERS IN SCIENTIFIC NOTATION SOLVE FOR THE UNKNOWN Use with Example Problem 3. Problem A: Problem State the problem. Solve the following problems. a. (2 × 103) × (3 × 102) a. (2 × 103) × (3 × 102) Multiply the coefficients. 2×3=6 b. (9 × 108) ÷ (3 × 10-4) Add the exponents. 3+2=5 Combine the parts. 6 × 105 Problem B: State the problem. b. (9 × 108) ÷ (3 × 10-4) Divide the coefficients. 9÷3=3 MULTIPLYING AND DIVIDING NUMBERS IN SCIENTIFIC NOTATION EVALUATE THE ANSWER SOLVE FOR THE UNKNOWN To test the answers, write out the original Problem B continued: data and carry out the arithmetic. For example, Problem a becomes 2000 × 300 = Subtract the exponents. 600,000, which is the same as 6 × 105. 8 − (−4) = 8 + 4 = 12 Combine the parts. 3 × 1012 Q/Solve each problem and express the answer in scientific notation a/ (4 x 102 ) x (1x 108 ) b/ (2x 10-4 ) x ( 3x 102 ) c/ (6 x 102 ) ÷ ( 2x 101 ) d/ (8 x 104 ) ÷ ( 4 x 101 )  Dimensional Analysis Dimensional analysis is a systematic approach to problem solving that uses conversion factors to move, or convert, from one unit to another. A conversion factor is a ratio of equivalent values having different units. Examples: Q/ convert the following units 1. 15 m to km 2. 20 cm to m 3. 25 mm to m Q/ convert the following units 1. 360 sec to min 2. 240 sec to min 3. 2.67 hour to second  Quiz 1. What are the SI base units of temperature? A kg B degrees Celsius C kelvins CORRECT D degrees Fahrenheit  Quiz 2. The density of water is 1.0 g/mL. What is the mass of 2.0 L of water? A 5.0 kg C 2.0 kg CORRECT B 0.002 kg D 0.50 kg  Quiz 3. The average distance from Earth to the Moon is 384,000 km. How would you write this distance in scientific notation? A 3.84 × 10-5 km B 0.384 × 10-6 km C 3.84 × 105 km CORRECT D 384 × 103 km  Quiz 4. The equation above is used to change from miles per hour to feet per second. This is an example of ______. A scientific notation C SI base units B conversion factoring D dimensional analysis CORRECT  Lesson 3 Uncertainty in Data  Focus Question Why are significant figures important?  New Vocabulary accuracy precision error percent error significant figures  Review Vocabulary dimensional analysis: a systematic approach to problem solving that uses conversion factors to move from one unit to another  Accuracy and Precision Accuracy refers to how close a measured value is to an accepted value. Precision refers to how close a series of measurements are to one another. Q/Why are accuracy and precision both important?  Error and Percent Error Error is defined as the difference between an experimental value and an accepted value. Percent error expresses error as a percentage of the accepted value. CALCULATING PERCENT ERROR KNOWN UNKNOWN Use with Example Problem 5. Accepted value for Percent errors = ? Problem density = 1.59 g/cm3 Use Student A’s density data in Table 3 (from Errors: −0.05 g/cm3; 0.01 slide 6) to calculate the percent error in each g/cm3; −0.02 g/cm3 trial. Report your answers to two places after the decimal point. Response ANALYZE THE PROBLEM You are given the errors for a set of density calculations. To calculate percent error, you need to know the accepted value for density, the errors, and the equation for percent error. CALCULATING PERCENT ERROR EVALUATE THE ANSWER The percent error is greatest for Trial 1, which had the largest error, and smallest for Trial 2, which was closest to the accepted value. Question The density of lead is 13.6 g/cm, but the measured and calculated value in lab was 14.9 g/cm what was the percent error ? Q/why is percent error important?  Significant Figures The precision of a measurement is indicated by the number of digits reported. The reported digits are called significant figures. Significant figures include all known digits plus one estimated digit.  Significant Figures Rules for significant figures Rule 1: Nonzero numbers are always significant. 72.3 g Rule 2: Zeros between nonzero numbers are always significant. 60.5 g Rule 3: All final zeros to the right of the decimal are significant.. 6.20 g Rule 4: Placeholder zeros are not significant. To remove placeholder zeros, rewrite the number in scientific notation. 0.0253 g 4320 g Rule 5: Counting numbers and defined constants have an infinite number of significant figures. 6 molecules / 60 s = min SIGNIFICANT FIGURES SOLVE FOR THE UNKNOWN Use with Example Problem 6. Rules 1, 2, and 3. Problem Count all nonzero numbers, zeros between Determine the number of significant figures nonzero numbers, and final zeros to the right of in the following masses. the decimal place. Rule 4. a. 0.00040230 g Ignore zeros that act as placeholders. b. 405,000 kg a. 0.00040230 g has five significant figures. Response b. 405,000 kg has three significant figures. ANALYZE THE PROBLEM EVALUATE THE ANSWER You are given two measured mass values. Apply the appropriate rules to determine the One way to verify your answers is to write the number of significant figures in each value. values in scientific notation: 4.0230 × 10-4 g and 4.05 × 105 kg. Without the placeholder zeros, it is clear that 0.00040230 g has five significant figures and that 405,000 kg has three significant figures.  Rounding Numbers Rounding : is used to simplify numbers , making them easier to work with and understand. 1.Simplification : Rounding makes numbers simpler and more manageable for example it’s easier to say 700,000 instead of 698,869.  Rounding Numbers Rules for Rounding Rule 1: If the digit to the right of the last significant figure is less than 5, do not change the last significant figure. 2.532 → 2.53 Rule 2: If the digit to the right of the last significant figure is greater than 5, round up the last significant figure. 2.536 → 2.54  Rounding Numbers Rules for Rounding Rule 3: If the digits to the right of the last significant figure are a 5 followed by a nonzero digit, round up the last significant figure. 2.5351 → 2.54 Rule 4: If the digits to the right of the last significant figure are a 5 followed by a 0 or no other number at all, look at the last significant figure. If it is odd, round it up; if it is even, do not round up. 2.5350 → 2.54 2.5250 → 2.52  Rounding Numbers Addition and subtraction Round the answer to the same number of decimal places as the original measurement with the fewest decimal places. Multiplication and division Round the answer to the same number of significant figures as the original measurement with the fewest significant figures. ROUNDING NUMBERS WHEN ADDING SOLVE FOR THE UNKNOWN Use with Example Problem 7. Align the measurements and add the Problem values. A student measured the length of his lab 28.0 cm partners’ shoes. If the lengths are 28.0 cm, 23.538 cm, and 25.68 cm, what is the total 23.538 cm length of the shoes? + 25.68 cm 77.218 cm Response ANALYZE THE PROBLEM Round to one place after the decimal; Rule The three measurements need to be aligned on 1 applies. their decimal points and added. The The answer is 77.2 cm. measurement with the fewest digits after the decimal point is 28.0 cm, with one digit. Thus, the EVALUATE THE ANSWER answer must be rounded to only one digit after The answer, 77.2 cm, has the same precision the decimal point. as the least-precise measurement, 28.0 cm. ROUNDING NUMBERS WHEN SOLVE FOR THE UNKNOWN MULTIPLYING Calculate the volume, and apply the rules of significant figures and rounding. Use with Example Problem 8. State the formula for the volume of a Problem rectangle. Calculate the volume of a book with the Volume = length × width × height following dimensions: length = 28.3 cm, width = 22.2 cm, height = 3.65 cm. Substitute values and solve. Volume = 28.3 cm × 22.2 cm × 3.65 cm = 2293.149 Response cm3 ANALYZE THE PROBLEM Round the answer to three significant figures. Volume is calculated by multiplying length, width, and height. Because all of the Volume = 2290 cm3 measurements have three significant figures, the answer also will. EVALUATE THE ANSWER KNOWN UNKNOWN To check if your answer is reasonable, round each measurement to one significant figure and Length = 28.3 cm Volume = ? cm3 recalculate the volume. Volume = 30 cm × 20 cm × 4 cm = 2400 cm3. Because this value is close to your Width = 22.2 cm calculated value of 2290 cm3, it is reasonable to Height = 3.65 cm conclude the answer is correct.  Quiz 1. Which term is defined as the difference between an experimental value and an accepted value? A accuracy B precision C error CORRECT D percent error  Quiz 2. Significant figures reflect the ______ of a measurement. A accuracy B precision CORRECT C error D percent error  Quiz 3. Which of the following has 3 significant figures? A 7.84 s CORRECT C 110 s B 0.004 s D 121.5 s  Quiz 4. What is 6.950 g rounded to 2 significant figures? A 6.95 g C 6.9 g B 6.96 g D 7.0 g CORRECT  Lesson 4 Representing Data  Focus Question How can displaying data help you interpret it? it helps people see, interact with, and better understand data  New Vocabulary graph independent variable dependent variable  Review Vocabulary base unit: a defined unit in a system of measurement that is based on an object or event in the physical world and is independent of other units  Graphing A graph is a visual display of data that makes trends easier to see than in a table. A circle graph, or pie chart, has wedges that visually represent percentages of a fixed whole. A pie chart helps organize and show data as a percentage of a whole  To produce a pie chart, data is required. The data often comes in the form of a table. To create a pie chart, the size of the angles needed must be calculated. Steps to make a pie chart 1.Add the total frequency in the table. 2.Divided 360° by the total frequency. 3.Multiply each frequency by this value. These are the angles for each sector. 4.Construct a circle and draw a vertical line from the top to the center. 5.In a clockwise direction, use a protractor to plot each angle in turn. 6.Label each sector or use a key to color code each. 7.Give your pie chart a title. Question A café owner recorded the type and number of drinks ordered in an hour. The table shows the results. If these were to be represented as a pie chart, what angle would be needed for each sector?  Graphing A bar graph is often used to show how a quantity varies across categories. Bar graphs are used to compare things between different groups or to track changes over time  Graphing Points on a line graph represent the intersection of two variables. The independent variable— the variable deliberately changed in an experiment — is plotted on the x-axis. The dependent variable—the value of which changes in response to the independent variable—is plotted on the y-axis.  Graphing If the best-fit line through the points is straight, the relationship is linear. If the best-fit line through the points is curved, the relationship is nonlinear. Linear relationships can be analyzed further by examining the slope of the line.  Interpreting Graphs Interpolation is reading and estimating values falling between points on the graph. Extrapolation is estimating values outside the points by extending the line. This graph helps the viewer compare two different time periods.  Quiz 1. What is the independent variable on this graph? A month CORRECT B total ozone C 1957-1972 D 1979-2010  Quiz 2. According to this graph, what is the greatest natural source of chlorine in the stratosphere? A CFC-12 B CFC-11 C Methyl chloride CORRECT D Hydrogen chloride  Quiz 3. Using extrapolation from this graph, what would you expect the temperature to be at sea level? A 15.5°C B 18.0°C C 20.0°C CORRECT D 0°C  Quiz 4. On this graph, the density of aluminum is ______. A the independent variable B the slope CORRECT C the inverse of the slope D the dependent variable