Unit 2 Measurements Significant Figures Scientific Notation Significant

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Unit 2 - Measurements. Significant Figures & Scientific Notation

Unit 2 - Measurements. Significant Figures & Scientific Notation

Significant Figures Ø Figures (values) that indicate precision of a measurement. Ø Recording Sig

Significant Figures Ø Figures (values) that indicate precision of a measurement. Ø Recording Sig Figs w Sig figs in a measurement include the known digits plus a final estimated digit 2. 35 cm

Counting Sig Figs Count all numbers EXCEPT: w Leading zeros: w 0. 0025 2

Counting Sig Figs Count all numbers EXCEPT: w Leading zeros: w 0. 0025 2 sig figs w Trailing zeros without a decimal point: w 2, 500 2 sig figs

Atlantic-Pacific Method Pacific Ocean PRESENT “_____” Atlantic Ocean ABSENT “ _______”

Atlantic-Pacific Method Pacific Ocean PRESENT “_____” Atlantic Ocean ABSENT “ _______”

Atlantic-Pacific Method: 1. Decimal point is PRESENT: Ø count significant figures from the LEFT

Atlantic-Pacific Method: 1. Decimal point is PRESENT: Ø count significant figures from the LEFT (Pacific side) Decimal point is ABSENT: Ø count significant figures from the RIGHT (Atlantic side) 2. Start counting significant figures at the first nonzero number and don’t stop until there are no more digits.

Practice Counting Sig Fig 1. 23. 50 4 sig figs 2. 402 3 sig

Practice Counting Sig Fig 1. 23. 50 4 sig figs 2. 402 3 sig figs 3. 5, 280 3 sig figs 4. 0. 080 2 sig figs 5. 0. 006700 4 sig figs

Practice Counting Sig Fig Ø Round the number at left to the number of

Practice Counting Sig Fig Ø Round the number at left to the number of significant figures stated in each column Number 4 sig figs 3 sig figs 2 sig figs 1 sig fig 80. 405 80. 4 1 80. 4 80. 80 29, 00 0 30, 00 0 29, 35 29, 40 0 0

Calculating Rules: Multiplying & Dividing : The # with the fewest sig figs determines

Calculating Rules: Multiplying & Dividing : The # with the fewest sig figs determines the # of sig figs in the answer. (13. 91 g/cm 3)(23. 3 cm 3) = 324. 103 g 4 SF 324 g

Calculating Rules: Adding & Subtracting: w The # with the lowest decimal value determines

Calculating Rules: Adding & Subtracting: w The # with the lowest decimal value determines the place of the last sig fig in the answer. 3. 75 m. L + 4. 1 m. L 7. 85 m. L 7. 9 m. L 224 g + 130 g 354 g 350 g

Significant Figures Practice Problems 1. 2. 066 g 2. 85. 6 cm 3. 38

Significant Figures Practice Problems 1. 2. 066 g 2. 85. 6 cm 3. 38 g 4. 1. 13 g

Scientific Notation Ø In science, numbers can be very small & very large (confusing!)

Scientific Notation Ø In science, numbers can be very small & very large (confusing!) Ø Numbers can be expressed in Scientific Notation: Mx n 10 1 ≤ M < 10 +n: large # -

Scientific Notation Ø To convert into Sci. Notation: w Move decimal until there’s 1

Scientific Notation Ø To convert into Sci. Notation: w Move decimal until there’s 1 digit to its left. (# of places moved = exponent) w Large # (>1) positive exponent Small # (<1) negative exponent w Only include sig figs. 65, 000 kg 6. 5 × 104 kg

Scientific Notation Practice Problems 1. 2, 400, 000 mg 2. 4 6 10 mg

Scientific Notation Practice Problems 1. 2, 400, 000 mg 2. 4 6 10 mg 2. 0. 00256 kg 2. 56 3. 7 10 -5 km 0. 00007 km 4. 6. 2 104 mm 62, 000 mm -3 10 kg

Calculating with Scientific Notation (5. 44 × 107 g) ÷ (8. 1 × 104

Calculating with Scientific Notation (5. 44 × 107 g) ÷ (8. 1 × 104 mol) = Type on your calculator: 5. 44 2 nd EE 7 ÷ 8. 1 2 nd EE 4 ENTER = 671. 6049383 = 670 g/mol = 6. 7 × 102 g/mol