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**Measurement and Precision NOTES You need your clicker (from the 1st Day)**

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**Equipment Scavenger Hunt Answers on my CP Chem page (on my website!)**

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Accuracy vs. Precision Accuracy is how close your measurement is to the actual or accepted value. Precision is the degree of “exactness” of a set of measurements – something you can repeat the same way again and again. Also, a number with more significant figures is more precise than one with less.

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**accurate (the average is accurate) not precise**

precise not accurate accurate and precise

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**The Basic Rules of Sig. Figs!**

NONzero Numbers are ALWAYS significant! (ex. ( !) 2. ZEROs within other nonzero numbers ARE sig. (ex all are significant!) 3. Zeros that are PLACE HOLDERS are NOT significant! ( or 50000) *However a decimal shows precision (50000.) We will use the DOT RIGHT, NOT LEFT method.

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When using or averaging a set of numbers, the final answer can only be as precise as THE LEAST precise number!!!!! Look for the number that is the least precise and round the answer to the same number of digits. For addition and subtraction: Line up the numbers and round to the last decimal place of the least precise number. Add the following set and round the answer to the correct number of places , , 15.2, For multiplication and division: Round the final answer to the same NUMBER of SIGNIFICANT FIGURES as the number of sig. fig.s in the least precise measurement. Example: x2001 = 100 (only 1 S.F.)

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**What is the most commonly used SI unit/units for the following?**

Mass – g (kg for physics) Length – m Volume – L (usually ml for chem) Density – g/ml or g/cc

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**Kilo- hecta- deka- X deci- centi- milli- micro- **

How to Convert???? The easy way: 1. Write down the scale or use the print out of the entire scale. Kilo- hecta- deka- X deci- centi- milli- micro- K h da base unit d c m µ (3 dec. places) Try 1g µg 2. Find out what unit you have. (grams) 3. Count the # of spaces you need to move. 4. Figure out what direction to go.

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**The metric system is based on multiples of 100.**

True False Response Grid

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**What is 5.0121 rounded to the hundredths place?**

None of these Response Grid

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**What is 5.0121 rounded to the tenths place?**

None of these Response Grid

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**What is 152,251 rounded to the hundreds place?**

152,000 152,250 152,300 Response Grid

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**What is 152,251 rounded to the thousands place?**

152,000 152,250 152,300 Response Grid

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**How many milliliters are there in a Liter?**

1 10 100 1000 Response Grid

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**The measurement 20.00 grams is more precise than 20 grams.**

True False Response Grid

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**Which of the following best describes the length of the beetle's body in the picture?**

1 to 2cm 1.5 to 1.6cm 1.54 to 1.56cm 1.546 to 1.547cm Response Grid

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If the black lines in the picture at left just touch the rim of the penny, which of the following best describes the penny's diameter? 1 to 2 1.9 to 2.0cm 1.92 to 1.94cm 1.935 to cm Response Grid

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**What can you estimate from the left ruler?**

1-2 in 1.5 in 1.45 in 1.450in Response Grid

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**What can you estimate from the RIGHT ruler?**

1-2 in 1.5 in 1.45 in 1.450in Response Grid

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**Levi collects the following measurements: 50. 33g, 50. 32g, 50**

Levi collects the following measurements: g, g, g The actual accepted value is grams, what can we say about his data? It is precise and accurate. It is precise, but not accurate. It is accurate, but not precise.

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**Katie collects the following measurements: 55. 63g, 55. 62g, 55**

Katie collects the following measurements: g, g, g The actual accepted value is grams, what can we say about her data? It is precise and accurate. It is precise, but not accurate. It is accurate, but not precise.

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**These two are equivalent:**

These two are equivalent: km in 230m and equal in number of significant digits. True False

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**Which number has 4 significant figures?**

1.00 1020 100. 1000. B and D

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**Bob is going to run 5km. This is the same as running 5000m.**

True False

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**Which number has the most significant figures?**

10 100 1000 They all have the same # of sig. figs

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**How many tablespoons are in a cup?**

10 12 14 16

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**There are 4 pecks in a bushel.**

True False

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