Scientists use scientific methods to systematically pose and test solutions to questions and assess the results of the tests. Section 2: Scientific Notation and Dimensional Analysis K What I Know W What I Want to Find Out L What I Learned

2(G)Express and manipulate chemical quantities using scientific conventions and mathematical procedures, including dimensional analysis, scientific notation, and significant figures. 2(H)Organize, analyze, evaluate, make inferences, and predict trends from data. Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education

Essential Questions Why use scientific notation to express numbers? How is dimensional analysis used for unit conversion? Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education

Review quantitative data New scientific notation dimensional analysis conversion factor Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education Vocabulary

Scientific Notation Scientific notation can be used to express any number as a number between 1 and 10 (known as the coefficient) multiplied by 10 raised to a power (known as the exponent). Carbon atoms in the Hope Diamond = 4.6 x 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. 800 = 8.0 × = 3.43 × 10 –5 Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education

Scientific Notation Addition and subtraction Exponents must be the same. Rewrite values to make exponents the same. Example: x x 10 17, you must rewrite one of these numbers so their exponents are the same. Remember that moving the decimal to the right or left changes the exponent x x Add or subtract coefficients. Ex x x = 3.2 x Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education

Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education SCIENTIFIC NOTATION Use with Example Problem 2. Problem Write the following data in scientific notation. a. The diameter of the Sun is 1,392,000 km. b. The density of the Sun’s lower atmosphere is g/cm 3. Response ANALYZE THE PROBLEM You are given two values, one much larger than 1 and the other much smaller than 1. In both cases, the answers will have a coefficient between 1 and 10 multiplied by a power of 10. SOLVE FOR THE UNKNOWN Move the decimal point to give a coefficient between 1 and 10. Count the number of places the decimal point moves, and note the direction. Move the decimal point six places to the left. Move the decimal point eight places to the right. Write the coefficients, and multiply them by 10 n where n equals the number of places moved. When the decimal point moves to the left, n is positive; when the decimal point moves to the right, n is negative. Add units to the answers. a × 10 6 km b. 2.8 × g/cm 3

Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education 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 umber less than 1, its exponent is negative.

Scientific Notation Multiplication and division To multiply, multiply the coefficients, then add the exponents. –Example: (4.6 x )(2 x ) = 9.2 x 10 0 To divide, divide the coefficients, then subtract the exponent of the divisor from the exponent of the dividend. –Example: (9 x 10 7 ) ÷ (3 x ) = 3 x Note: Any number raised to a power of 0 is equal to 1: thus, 9.2 x 10 0 is equal to 9.2. Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education

Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education MULTIPLYING AND DIVIDING NUMBERS IN SCIENTIFIC NOTATION Use with Example Problem 3. Problem Solve the following problems. a. (2 × 10 3 ) × (3 × 10 2 ) b. (9 × 10 8 ) ÷ (3 × ) SOLVE FOR THE UNKNOWN Problem A: State the problem. a. (2 × 10 3 ) × (3 × 10 2 ) Multiply the coefficients. 2 × 3 = 6 Add the exponents = 5 Combine the parts. 6 × 10 5 Problem B: State the problem. b. (9 × 10 8 ) ÷ (3 × ) Divide the coefficients. 9 ÷ 3 = 3

Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education MULTIPLYING AND DIVIDING NUMBERS IN SCIENTIFIC NOTATION SOLVE FOR THE UNKNOWN Problem B continued: Subtract the exponents. 8 − ( − 4) = = 12 Combine the parts. 3 × EVALUATE THE ANSWER To test the answers, write out the original data and carry out the arithmetic. For example, Problem a becomes 2000 × 300 = 600,000, which is the same as 6 × 10 5.

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. Writing conversion factors: Conversion factors are derived from equality relationships, such as 1 dozen eggs = 12 eggs. Percentages can also be used as conversion factors. They relate the number of parts of one component to 100 total parts. Using conversion factors: A conversion factor must cancel one unit and introduce a new one. Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education

Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education USING CONVERSION FACTORS Use with Example Problem 4. Problem In ancient Egypt, small distances were measured in Egyptian cubits. An Egyptian cubit was equal to 7 palms, and 1 palm was equal to 4 fingers. If 1 finger was equal to mm, convert 6 Egyptian cubits to meters. Response ANALYZE THE PROBLEM A length of 6 Egyptian cubits needs to be converted to meters. KNOWNUNKNOWN Length = 6 Egyptian cubits length= ? g 7 palms = 1 cubit 1 palm = 4 fingers 1 finger = mm 1 m = 1000 mm

Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education USING CONVERSION FACTORS EVALUATE THE ANSWER Each conversion factor is a correct restatement of the original relationship, and all units except for the desired unit, meters, cancel.

Scientific Notation and Dimensional Analysis Copyright © McGraw-Hill Education Review Essential Questions Why use scientific notation to express numbers? How is dimensional analysis used for unit conversion? Vocabulary scientific notation dimensional analysis conversion factor