Chapter 2 Significant Digits. Taking Measurements All measurements involve one estimation. If the measuring device is digital it will take the estimation.

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Presentation transcript:

Chapter 2 Significant Digits

Taking Measurements All measurements involve one estimation. If the measuring device is digital it will take the estimation for you.

Electronic Measuring Devices Digital readout measuring diameter of inches. The last zero is the estimated digit.

Taking Measurements All measurements involve one estimation. If the measuring device is scaled you must take the estimation yourself.

Scaled Measuring Devices

Bottom ruler gives a measurement of 8.? cm.

Scaled Measuring Devices Measure the length of the metal using the top ruler.

How to read a meniscus.

Read the Volume in mL

Significant Digits

Rules for Significant Digits All non-zero digits are significant. “Trailing” zeros after the decimal point ARE significant. Zeros between significant digits are significant. All other zeros are NOT significant unless indicated to be so by having a bar placed over them.

How to Determine Significant Digits Underline the leftmost nonzero digit. Use the rules for significant digits to determine the rightmost significant digit. Every digit in between the leftmost and rightmost significant digits are significant as well.

Counting or Exact Numbers Counting numbers: If there are 10 people in a room there are not 9.5 or people in the room. Counting numbers are exact. Ones in Conversion Factors: 1 kilometer = 1000 meters. Exactly 1 km is equal to exactly 1000m. The 1 is considered to be an exact number and so is the Since Counting numbers and metric conversions are exact they have an infinite number of significant digits.

Determine the Significant Digits (Examples in Notebook) L mg µm 27.0 km 50 people cm 200 kg ºC 1000 mL 42, cm 225 beans dm m 3,200,000 µL

Determine the Significant Digits (Examples in Notebook) L mg µm km 3 50 people infinite cm kg ºC mL 1 42, cm beans infinite dm m 4 3,200,000 µL 5

Math Operations with Significant Digits When multiplying and/or dividing your answer must reflect the smallest number of significant digits.

Math Operations with Significant Digits When multiplying and/or dividing your answer must reflect the smallest number of significant digits. (17.3 cm)(28 cm) = cm 2

Math Operations with Significant Digits When multiplying and/or dividing your answer must reflect the smallest number of significant digits. (17.3 cm)(28 cm) = cm 2 = 480 cm 2

Math Operations with Significant Digits When multiplying and/or dividing your answer must reflect the smallest number of significant digits. (17.3 cm)(28 cm) = cm 2 = 480 cm 2 708g ÷ 4.700ml = g/ml =

Math Operations with Significant Digits When multiplying and/or dividing your answer must reflect the smallest number of significant digits. (17.3 cm)(28 cm) = cm 2 = 480 cm 2 708g ÷ 4.700ml = g/ml = 151g/ml

Addition and/or Subtraction reflects the fewest decimal places decimal places cm − cm = 7.59 cm

Addition and/or Subtraction reflects the fewest decimal places decimal places cm − cm = 7.59 cm = 7.6 cm

Addition and/or Subtraction reflects the fewest decimal places decimal places cm − cm = 7.59 cm = 7.6 cm 8.5g g g =

Addition and/or Subtraction reflects the fewest decimal places decimal places cm − cm = 7.59 cm = 7.6 cm 8.5g g g = 10g

Addition and/or Subtraction reflects the fewest decimal places decimal places cm − cm = 7.59 cm = 7.6 cm 8.5g g g = 10g = 10.0g

Homework  Worksheet – Significant Digits & Rounding.