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Do Now

Do Now. Take out homework packet, do #1 on page 19. Measurement Quiz. Tonight's Homework. Read page 9-10 for the next topic Homework Packet p 19+20 Watch Rosengartens video (1.03 rounding) and take a look at the homework (3).

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Do Now

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Presentation Transcript

  1. Do Now • Take out homework packet, do #1 on page 19

  2. Measurement Quiz

  3. Tonight's Homework • Read page 9-10 for the next topic • Homework Packet p 19+20 • Watch Rosengartens video (1.03 rounding) and take a look at the homework (3). • Write down at least 2 questions to ask for the next class. There will be questions on the daily quiz from the reading (15 minutes)

  4. Todays Goal • Be able to determine a numbers precision and the number of significant figures • Take out your note packets and turn to page 7

  5. What the heck are significant figures? • Good question…… • Significant = important • Figures = numbers • Aren’t all numbers important? • Not always

  6. Significant vs. Insignificant • Numbers we know for sure from measurement are significant • Numbers that we don’t know are not • Example: • 13.5 ml • Precision was to the tenths, so we know all of those numbers for sure • 210 g • Our precision stopped at the 1 in the tens place • We don’t know what the zero is so it is not significant

  7. Significant vs. Insignificant • 00031 g • Do the zeros to the left count for anything? • No, they are insignificant • Zeros to the LEFT of the first integer are insignificant • .00073 l • The 7 and 3 are significant.

  8. Determining the number of Sig figs • 1) Look at the number • 2) Determine what the precision is • 3) Count from the left to the right, starting with the first non-zero and ending at the precision • 132.1 g

  9. Number Does it have a decimal? No Yes Precision is farthest # on right Precision is right most non-zero or a zero w/a line over it Count from the left most non-zero to the precision

  10. What is precision? • Being exact and accurate

  11. 2) Rosengartens rules for determining precision • How numbers are written will tell you the precision of the number • 1) If the measurement has a decimal point in it, the precision is the place furthest to the right in the measurement • Ex: 23.004 cm • Precision is to the thousandths

  12. More examples • 0.3320 g • Ten thousandths • 330. mL • Ones

  13. If the measurement does not have a decimal point in it… • The precision is the place where either the rightmost integer is, or where a zero with a line over it is (p8) • 2300 km • Hundreds

  14. More Examples • 1700 g • 1,000,000 joules • 17 ml • 10 ml

  15. Rosengarten’s Rule for Sig Fig’s • The number of significant figures in a measurement equals the total number of digits from and including the first (leftmost) integer in the measurement all the way to the limit of precision of that measurement. • Ex; 23.285 cm • Precision is to the…….. • Thousandths….so how many sig figs? • 5!

  16. To the tune of “To the left” • To the left, to the left, start counting at the first non-zero to the left • Count To the right till you reach the precision

  17. 3100 m • So how many sig figs? • 3100 m precision ends at the #1 • Count from the first non-zero on the left, to the precision…. • 2 sig figs

  18. What about 3100. m? • Oooo, a decimal point! What does that mean for the precision? • 3100. Precise to the 0 in the ones place • Count from the first non-zero on the left to the precision…. • 4 sig figs!

  19. What if it was a small number? • Lets say; 0.09053 kJ • Precision is to the…..hundred thousandths • .09053 kJ • Count from the first non-zero number on the left (9) to the precision. How many sig figs? • 4 sig figs!

  20. Wait, why ignore the 0 in the tenths? • Its kind of like all the 0’s that are to the left of any number. • 3200 m could be written 000003200 m • The zeros to the left of the first number are insignificant

  21. Ex: 0.050600 mol • Precision? • Millionths place; 0.050600 • First non-zero number; 0.050600 • Total number of sig figs? • 5

  22. Practice: How many sig figs • 2310. g • .09 km • 2300.100 J • 3.14 mg • 56.364327 L

  23. Cool • Take this time to do your homework (#2, p 19-20) and have me check it • YOUR HOMEWORK FOR TONIGHT • Read page 9-10 for the next topic, watch Rosengartens video (1.03 rounding) and take a look at the homework (3). Write down at least 2 questions to ask for the next class. There will be questions on the daily quiz from the reading • Check out wcsdchem.wordpress.com

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