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## PowerPoint Slideshow about 'SI units and sig figs' - frye

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- 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.
- Ex: the bullseye would be the true value, so these points are accurate.

Using sig figs: The Rules! of what is being measured.

- 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.

Multiplying and Dividing of what is being measured.

- 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.

Adding and Subtracting: of what is being measured.

- 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

Scientific Notation of what is being measured.

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

- 123,000,000,000 in s.n. is of what is being measured.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.

To write a large number in scientific notation: of what is being measured.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

To write a small number in s.n. of what is being measured.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

Significant Digits of what is being measured.

- 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.

Read the ruler of what is being measured.

SI Prefixes of what is being measured.

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