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THE METRIC SYSTEM. WHY DO WE USE THE METRIC SYSTEM?. Almost all other countries are using the metric system Scientists need a universal way to communicate data (SI Units). THE METRIC CONVERSION CHART (STAIRCASE METHOD). To convert to a smaller unit, move decimal point to the right or - PowerPoint PPT Presentation
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THE METRIC SYSTEM
WHY DO WE USE THE METRIC SYSTEM?
Almost all other countries are using the metric system
Scientists need a universal way to communicate data (SI Units)
THE METRIC CONVERSION CHART (STAIRCASE METHOD)
Kilo1000units
Hecto100units
Deka10
unitsBasic Unit Deci
0.1units
Centi0.01units
Milli0.001units
To convert to a smaller unit, movedecimal point to the right or
multiply.
To convert to a larger unit, movedecimal point to the left or divide
YouTube - metric conversions - shortcut method
Do the following conversions… 1678 mg to kg’s _____________ 456 liters to ml’s ____________ 6,789,000 mm’s to km’s
_____________ 1 liter to dl’s _____________ 45 cm’s to km’s _______________
TRY THIS USING THE STAIRCASE METHOD
1000 mg = ______ g
Step 1: Determine if you are going to go up or down the ladder.Step 2: Determine how many steps there are from milligrams to grams.Step 3: Move the decimal point the amount of places that was determined in steps 1 & 2.
TRY THIS USING THE STAIRCASE METHOD
1000 mg = ______ g
Step 1: Determine if you are going to go up or down the ladder.Step 2: Determine how many steps there are from milligrams to grams.Step 3: Move the decimal point the amount of places that was determined in steps 1 & 2.
1
TRY THIS USING THE STAIRCASE METHOD
.15 L = __________ ml
TRY THIS USING THE STAIRCASE METHOD
.15 L = __________ ml150
Scientific Notation
A short-hand way of writinglarge numbers without writing all of the zeros.
The Distance From the Sun to the Earth
93,000,000
Step 1
Move decimal left Leave only one number in front of
decimal
Step 2
Write number without zeros
Step 3
Count how many places you moved decimal
Make that your power of ten
The power often is 7 becausethe decimalmoved 7 places.
93,000,000 --- Standard Form
9.3 x 107 --- Scientific Notation
Practice Problem
1) 98,500,000 = 9.85 x 10?
2) 64,100,000,000 = 6.41 x 10?
3) 279,000,000 = 2.79 x 10?
4) 4,200,000 = 4.2 x 10?
Write in scientific notation. Decide the power of ten.
9.85 x 107
6.41 x 1010
2.79 x 108
4.2 x 106
More Practice Problems
1) 734,000,000 = ______ x 108
2) 870,000,000,000 = ______x 1011
3) 90,000,000,000 = _____ x 1010
On these, decide where the decimal will be moved.
1) 7.34 x 108 2) 8.7 x 1011 3) 9 x 1010
Complete Practice Problems
1) 50,0002) 7,200,0003) 802,000,000,000
Write in scientific notation.
1) 5 x 104 2) 7.2 x 106 3) 8.02 x 1011
Scientific Notation to Standard Form
Move the decimal to the right
3.4 x 105 in scientific notation
340,000 in standard form
3.40000 --- move the decimal
Write in Standard Form
6.27 x 106
9.01 x 104
6,270,000 90,100
Significant Figures
1.8
• Any digit that is not zero is significant
1.234 kg 4 significant figures• Zeros between nonzero digits are significant
606 m 3 significant figures• Zeros to the left of the first nonzero digit are not significant
0.08 L 1 significant figure• If a number is greater than 1, then all zeros to the right of the
decimal point are significant
2.0 mg 2 significant figures• If a number is less than 1, then only the zeros that are at the
end and in the middle of the number are significant
0.00420 g 3 significant figures
How many significant figures are in each of the following measurements?
24 mL 2 significant figures
3001 g 4 significant figures
0.0320 m3 3 significant figures
6.4 x 104 molecules 2 significant figures
560 kg 2 significant figures
1.8
Significant Figures
1.8
Addition or Subtraction
The answer cannot have more digits to the right of the decimalpoint than any of the original numbers.
89.3321.1+
90.432 round off to 90.4
one significant figure after decimal point
3.70-2.91330.7867
two significant figures after decimal point
round off to 0.79
If you round off to a “5”, if the next digit is ODD, round up. If it is EVEN, round down (leave it)!
Significant Figures
1.8
Multiplication or Division
The number of significant figures in the result is set by the original number that has the smallest number of significant figures
4.51 x 3.6666 = 16.536366 = 16.5
3 sig figs round to3 sig figs
6.8 ÷ 112.04 = 0.0606926
2 sig figs round to2 sig figs
= 0.061
Significant Figures
1.8
Multiplication or Division
The number of significant figures in the result is set by the original number that has the smallest number of significant figures
4.51 x 3.6666 = 16.536366 = 16.5
3 sig figs round to3 sig figs
6.8 ÷ 112.04 = 0.0606926
2 sig figs round to2 sig figs
= 0.061
Accuracy – how close a measurement is to the true value
Precision – how close a set of measurements are to each other
accurate&precise
precisebutnot accurate
not accurate¬ precise
1.8
1.9
Dimensional Analysis Method of Solving Problems
1. Determine which unit conversion factor(s) are needed
2. Carry units through calculation
3. If all units cancel except for the desired unit(s), then the problem was solved correctly.
1 L = 1000 mL
How many mL are in 1.63 L?
1L
1000 mL1.63 L x = 1630 mL
1L1000 mL
1.63 L x = 0.001630L2
mL
The speed of sound in air is about 343 m/s. What is this speed in miles per hour?
1 mi = 1609 m 1 min = 60 s 1 hour = 60 min
343ms
x1 mi
1609 m
60 s
1 minx
60 min
1 hourx = 767
mihour
meters to miles
seconds to hours
1.9