Bell Ringer Notebook Setup Name on inside front

Bell Ringer: Notebook Setup Name on inside front cover We will # each page front & back Start by numbering all you pages to 20 (only 10 sheets of paper)

Bell Ringer: Copy down objective in header • Pg 11 - Express numbers in scientific and standard notation to the correct number of significant figures. • Homework: watch math measurement video (will be posted to Edmodo & hollickchemistry. weebly. com) Take notes on page 12

When would we need to use scientific notation? • When measurements are REALLY BIG or REALLY SMALL • The Earth’s circumference is 4. 0075 x 107 meters OR 4. 0075 x 10 x 10 More convenient to shorten using scientific notation

Scientific notation rules notes • The coefficient must be greater than or equal to _____ and less than ____.

Scientific notation rules notes • Decimal always goes BEHIND the first non-zero digit • Count how many times you must move the decimal • If the number is BIG the exponent is POSITIVE • If the number is SMALL the exponent is NEGATIVE Coefficient Value x 10 Exponent

Scientific notation Practice 0. 225 L 44, 163 g 0. 0000091 m

Standard Notation 6. 750 x 102 g 4. 35 x 10 -4 L 3. 164 x 108 m

How precise can you be? Significant Figures

What is the difference between the following numbers? 20. Remember, when reading a measurement you can only estimate one place past the smallest increment. 20. 00 30 25 21 20 20 20 10 15 19

What are significant figures? The digits in a number that tell you the precision of the measurement that generated them 5 6 7 8

Instrumentation & Measurment • More divisions of measurement the more EXACT we can be. • The more decimals the more exact a measurement is

How can we increase accuracy? • Increasing the numbers of significant digits! • Significant digit- all numbers in a measurement plus an extra for estimation. 6. 60 m. L 6. 63 m. L

Why are there significant figures? • Equipment can only give you so many decimal places… • you cannot be more or less precise than your equipment’s smallest increment. • Calculators can give you too many or too few decimal places • we need to know when to stop.

Rules for recognizing significant figures Rule #1: Non-zero digits and zeros between nonzero digits are always significant. In other words, non-zero numbers and any zeros sandwiched between them are always significant. 1974 23516 4 sig figs 5 sig figs 2006. 8 5 sig figs 19806 5 sig figs

Rule #2: Leading zeros are not significant. In other words, leading zeroes at the beginning of a decimal are not significant. 0. 0253 0. 001111 3 sig figs 4 sig figs 2 sig figs 1. 111 x 10 -3 8. 3 x 10 -7 2. 53 x 10 -2 0. 00000083

Rule #3: Zeros to the right of all non-zero digits are only significant if a decimal point is shown. In other words, trailing zeroes at the end of a number that does not have a decimal point are not significant. 286. 0 4 sig figs 845. 10 4320 100. 3 sig figs 83, 000 5 sig figs 2 sig figs

Rule #4: For values written in scientific notation, the digits in the coefficient are significant. 6. 02 x 1023 3 sig figs 7. 998 x 10 -3 4 sig figs 4. 320 x 103 4 sig figs

Rule #5: When multiplying or dividing your final answer has the same amount of significant figures as the lowest given number. 65, 400 x 5. 0 =

Precision vs. Accuracy • Precision: How repeatable is the measurement? • Compare your measurement to other measurements you have taken with the same piece of equipment to determine precision. • Accuracy: How “correct” is the measurement? • Compare your measurement to a known standard to determine accuracy.

Precision vs. Accuracy Let’s draw some bullseyes: Accurate Precise

Precision vs. Accuracy Let’s draw some bullseyes: Accurate & Precise Neither Accurate or Precise

How many “points” do you need to prove • Accuracy, you need only 1 “point” • Precision, you need many points (at least 3)

Sci Notation in the calculator

Calculations with Sig Figs Example 2: 9. 63 x 1012 8. 17 x 10 -5

Calculations with Sig Figs Example 3: 99, 999. 99 / 0. 001 =

Calculations with Sig Figs Example 4: 3. 0 x 4 =