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SI units and sig figs

SI units and sig figs. SI (système internationale). Precision: the reproducibility, under the same conditions, of a measurement . These points are precise with one another but not accurate. Accuracy: the closeness of a measurement to the true value of what is being measured.

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SI units and sig figs

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  1. SI units and sig figs

  2. SI (système internationale)

  3. Precision: the reproducibility, under the same conditions, of a measurement . • These points are precise with one another but not accurate.

  4. Accuracy: the closeness of a measurement to the true value of what is being measured. • Ex: the bullseye would be the true value, so these points are accurate.

  5. Using sig figs: The Rules! • Digits from 1-9 are always significant. • Zeros between two other significant digits are always significant • One or more additional zeros to the right of both the decimal place and another significant digit are significant. • Zeros used solely for spacing the decimal point (placeholders) are not significant.

  6. Multiplying and Dividing • RULE: your answer may only show as many sig figs as the multiplied or divided measurement showing the least number of significant digits. • Example: 22.37 cm x 3.10 cm = 69.3 only 3 sig figs allowed.

  7. Adding and Subtracting: • RULE: your answer can only show as many decimal places as the measurement having the fewest number of decimal places. • Example: 3.76 g + 14.83 g + 2.1 g = 20.7 g

  8. Scientific Notation • Scientists have developed a shorter method to express very large numbers. • Scientific Notation is based on powers of the base number 10.

  9. 123,000,000,000 in s.n. is 1.23 x 1011 • The first number 1.23 is called the coefficient. It must be between 1 - 9.99 • The second number is called the base . The base number 10 is always written in exponent form. In the number 1.23 x 1011 the number 11 is referred to as the exponent or power of ten.

  10. To write a large number in scientific notation:ex: 36 000 • First put the decimal after the first digit and drop the zeroes. Ex: 3.6 • Next, count the number of places from the decimal to the end of the number. Ex: 4 • Finally, put it together. Ex: 3.6 x 104

  11. To write a small number in s.n.ex: 0.00064 • First move the decimal after the first real number and drop the zeroes. Ex: 6.4 • Next, count the number of places moved from the original decimal spot to the new decimal spot. Ex: 4 • Numbers less than 1 will have a negative exponent. Ex: -4 • Finally, put it together. Ex: 6.4 x 10-4

  12. Significant Digits • When using a measuring device, there is a last number estimation. • The accuracy of the sig figs depends upon the measuring device. • Ex: a ruler.

  13. Read the ruler

  14. SI Prefixes

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