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Published byOsborne Bradford Modified over 8 years ago
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MEASUREMENT
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Which of the following are measurements? 300lbs 80 marbles 6mL 45km/h 30 degrees Celsius 5ft 6in 16 fingers 5 acres of land
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Measurement Measurement – quantity that has both a number and a unit Scientific notation – a number written as the product of two numbers. Can you guess the following famous numbers? 3.0 x 10 8 m/s Speed of light 4×10 7 m Earth’s circumference
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Scientific Notation Write these numbers in scientific notation: 345000000 .00000345 111111 90 Write these in long form: 5.6 x 10 2 9.99 x 10 -11 1 x 10 190
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Accuracy and Precision Accuracy: measure of how close a measurement comes to the actual value Precision: how close a series of measurements are to one another ***Can have one without the other! Eg dart board
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Accuracy and Precision 1. 78 C, 76 C, 75 C 2. 77 C, 78 C, 78 C 3. 80 C, 81 C, 82 C Which of these is the most precise? Set 2, measurements closest together. Which is the most accurate? We would need to know the accepted value.
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Error in measurements Error = experimental value – accepted value Experimental value – the measurement in the lab Accepted value – the correct value. Error can be positive or negative. If the boiling point of water measure in the lab is 99.1 C, what is the error? Percent error = ___ error _ x 100% accepted value What is the percent error in the above question?
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Significant Figures Significant figures – include all the digits that are known and one last digit that is unknown. If you went to Walmart and the mangoes you were going to buy weighed 2.64lbs which digits are known and unknown? Sig figs are important because sometimes the number or calculation can be greatly affected by the number of significant figures in the values used.
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Read pg. 66/67 Rules for determining whether a digit in a measured value is significant. What are the 6 rules?
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Rules for determining if a digit in a measured value is significant 1. Every non-zero digit is significant. 2. Zeros between non-zeros are significant. 3. Left-side zeros are placeholders. Eg. 0.007 4. Zeros to the right of the decimal and at the end of a number are significant. Eg. 15.60 5. Zeros at the rightmost end of a measurement before a decimal point can be placeholders or significant. Eg. 300 (not significant) and 3.00 x 10 2 (significant). 6. There are 2 situations when there can be an unlimited number of sig figs. 1 – when you count. 2 – defined quantities like 1min = 60 seconds.
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Pg. 72 q’s 10, 11, 13, 14
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Read pgs 68-71
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