Measurement/Calculation

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# Measurement/Calculation - PowerPoint PPT Presentation

Measurement/Calculation. Units of Measure. Metric System. based on powers of ten, so it’s easy to convert between units. Remember: KING HENRY DANCED BEFORE DAWN COUNTING MONEY Or KING HENRY DIED BY DRINKING CHOCOLATE MILK. Units. How to use. Right. Kilo. Hecto. Deka. BASE. Deci.

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## Measurement/Calculation

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Presentation Transcript

### Measurement/Calculation

Units of Measure

Metric System
• based on powers of ten, so it’s easy to convert between units.
• Remember:
• KING HENRY DANCED BEFORE DAWN COUNTING MONEY
• Or
• KING HENRY DIED BY DRINKING CHOCOLATE MILK
How to use

Right

Kilo

Hecto

Deka

BASE

Deci

Centi

Milli

Left

Examples

Kilo

Hecto

Deka

• 20 L= _______ mL
• 7 kg = _______ mg
• 90 mm = _______ cm
• 223 mL = ________ L
• 0.49 hm = ______ m

BASE

Deci

Centi

Milli

20 000

7 000 000

9.0

0.223

49

SI derived units

(derived units are calculated from base units)

NOTE:
• 1 cm3 IS EQUAL TO 1 mL!!!
• And a cc is the same as a cm3

### Measurement/Calculation

Scientific Notation/Accuracy &Precision

Rules to putting into Sci Not
• Must have a whole number between 1- 9
• If you move:
• Decimal toLeft…exponent is Positive
• Decimal to Right...exponent is Negative
Examples
• .0032
• 15 300 000

3.2 X 10-3

1.53 X 107

Examples
• 5.00 X 104
• 2.32 X10-3

50 000

5.00

0

0

.00232

0

0

2.32

• Make exponents the same by moving decimal place and changing exponent
• Then add/subtract and put in correct Sci Not

OR

Change mode to Sci

EXP

EXP

EE

EE

Example

5.00 X 104

+ .244 X 104

5.00 X 104

+ 2.44 X 103

5.244X 104

OR

Enter

5.00

4

3

+

2.44

Multiplication/Division
• Multiplication
• Multiply numbers
• Division
• Divide numbers
• Subtract exponents
• Then put back in correctscientific notation!

EXE

EXP

EXP

ENTER

EE

EE

Example

(5.44 × 107 g) ÷ (8.1 × 104 mol) =

= 6.7 × 102 g/mol

=0.67 X 103 g/mol

5.44

7

8.1

4

÷

= 671.6049383

= 670 g/mol

= 6.7 × 102 g/mol

Accuracy and Precision
• Accuracy: how close a measurement is to the true value (the “correct answer”)
• Precision: how close a value is to other values in that series

Are the following groups of measurements accurate, precise, both, or neither?

• 1) Given: true mass of sample of zinc is 14.5 g
• 13.2 g, 15.6 g, 17.9 g, 12.0 g
• Given: true volume of sample of water is 33.3mL
• 22.4 mL, 22.2 mL, 22.4 mL, 22.3 mL
• 3) Given: true length of copper wire is 58.5 cm
• 58.4 cm, 58.5 cm, 58.5 cm, 58.4 cm

Qualitative: a descriptive measurement (quality); does not involve numbers

Quantitative: a numerical measurement (quantity)

### Measurement/Calculation

Significant Figures

Rules to Significant Figures
• If it’s not 0, it counts.
• Example
• 743.44
• 24

5

2

Rules to Significant Figures
• 0’s in between significant figures count.
• Example
• 506
• 20405
• .707

3

5

3

Rules to Significant Figures
• All 0’s at the end past the decimal point count.
• Example
• 2.440
• 784.30

4

5

Rules to Significant Figures
• 0’s as placeholders don’t count.
• Example
• 440
• 0.09

2

1

Alternative Way

Atlantic

(Absent)

Pacific

(Present)

Pacific

(Present)

Atlantic

(Absent)

• If the decimal is present, start on the Pacific side at the first nonzero digit and count it and all the digits to the right of it.
• If the decimal is absent, start on the Atlantic side at the first nonzero digit and count it and all the digits to the left of it.
• The answer has only as many decimal places as the measurement having the least number of decimal places.
• Example

190.2 g

65.291 g

12.38 g

267.871 g

1

3

2

267.9 g

Answer should have 1 decimal place

Multiplication/Division

Mult/Divide First

• The answer has only as many significant figures as the measurement with the least number of significant figures.
• Example

13.78 g

11.3 mL

4

3

1.22 g\ml

= 1.219469 g/mL

Answer should have 3 significant figures

2

• 5
• 2
• Example
• 15000
• 2030.0
• 0.0020

### Measurement/Calculation

Density

Density
• Derived unit
• g/mL or g/cm3
• Mass/Volume
D. Density
• An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass.

GIVEN:

V = 825 cm3

D = 13.6 g/cm3

m = ?

WORK:

m = DV

m = (13.6 g/cm3)(825cm3)

m = 11 220 g=11 200g

WORK:

V = m

D

V = 25 g

0.87 g/mL

D. Density
• A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid?

GIVEN:

D = 0.87 g/mL

V = ?

m = 25 g

V = 28.74mL = 29 mL

WORK:

D = m

V

D = 5.6 g

3.4 mL

D. Density
• A marble has a mass of 5.6 g. It is placed in a graduated cylinder with 50.0 mL of water. The water level rises to 53.4 mL. What is the density of the marble?

3.4 mL

GIVEN:

D = ?

V = 53.4-50 =3.4 mL

m = 5.6 g

D=1.647 g/mL = 1.6 g/mL

Graphing

Graphing is an important tool for expressing data so that it is easier to read and interpret

Rules for graphing:

--place the manipulated/independent variable (the one that was changed) on the x axis.

--place the dependent/responding variable (the results of that change) on the y axis.

(dry mix)

DRY

MIX

y scale = largest y value – smallest y value x scale = largest x value – smallest x value

# of lines on the y axis # of lines on the x axis

The graph should cover at least ¾ of the grid