chapter 3

Measurement and Uncertainty

Textbook MeasurementsAs Measured Converted to m SigFig

meter 0.3 m .3 m

decimeters 2.7 dm .27 m

Centimeters 27.5 cm .275 m

Millimeters 275.0 mm .2750 m

• The measurement gives significance to each digits.• What does the Whole represent and the decimal in the first

column?• When the numbers converted, where is the estimated value?

DO NOW

• Color is intrinsic• Density is qualitative• Mass is intrinsic• Chemical change:

• Cooking mixing• Evaporating burning• Dissolving rusting• Distillation

What state of matter can change volume?What is air?

Some Basics

• Measurement is fundamental to experimental science.• Measurements have TWO parts: The numeric part and the unit.

LEQ’s

• What is measurement?• What are accuracy and

precision?• What are significant figures and

how do you determine them?

Uncertainty in Measurement

• Different measuring tools have different levels of ___________.

Ruler Measurement • For best measurement be sure you use zero, not the end of rule.• Measure to one place beyond

what is marked.

A1 = 6.70

Accuracy and Precision

•Accuracy = Nearness to known or actual value. SO your measurements are compared to outside measurement.

•Precision = Nearness in repetitions.So your measurements are compared to each

other

• http://www.sophia.org/tutorials/accuracy-and-precision--8

Error

• Error = Experimental – Accepted• The number show how much it was off by.• The sign show direction ( + higher than expected; - lower than expected)

|error|

• Percent Error = accepted x100

Significant Figure

•Refer to the digits that were measured + one estimated.•When rounding , we must pay attention to significant

figures so that we do not overstate or understate the accuracy of our answers.•Here’s more•Handout with rules.

Examples of SigFigs

•123 m•40,506 mm•9.8000 x 104

•22 meter sticks• .070 80 m•98,000 m

Add/Subtract: Round to the least precise•12.54 m+ 349.0 m+ 8.24 m =

•14.2 g – 8.73 =

Mult./Division : Round to the lowest sigfig•7.55 m x 0.34 m =

•2.10 m x 0.70 m =

•2.4526 cm / 8.4 =

SI Units

• LEQ: • What are the base units for the metric system and the SI system?• What are the prefixes used in the metric that I need to know?• How do you convert between metric units?

Common Base Units

Measurement Unit

Length

Mass (SI base= )

Volume

Time

Temperature

energy

Prefixes for SI

Name Abbreviation Value

Giga

Mega

Kilo

Hecto

Deka

Deci

Centi

Milli

micronano

Example and explanation of converting

Crime Fighting Data Chart

Suspect Mass Mass (g) Volume Volume (L) length

Kelvin –vs- Celsius

C = K – 273.15K = C + 273.15

What are 10 -12 Boo? PicoBoo

3.3 LEQ

•How are equivalencies and ratios used to change units and solve problems?

How many seconds are in an 8 hour day?

8 hours x ------ = minutes

min. x ------ = minutes

The directions for an experiment call for 1.84g Cu for each student. There are 50.0g. How many students can do the experiment?

50.0 g Cu x ------ = students

What is .073 cm in micrometers?

Density is the mass/unit volume. The density of Manganese is 7.21 g/cm3.

What would that be in Kg/m3?

What do you call 2000 Mockingbird?

2 KiloMockingbird

Density and Its Application

•What is density?•How can density be used to solve problems?

Density

•Density is an intrinsic property of matter.•It describes “how tightly matter is packed”•Density = Mass VolumeUnits: g/cm3 or Kg/m3 or g/L or g/mL

(derived units)

Density d= m/v

Density generally decreases as temperature increases.

Water is one of the special!

1) A block of aluminum occupies a volume of 15.0 mL and weighs 40.5 g. What is its density?

A rectangular block of copper metal weighs 1896 g. The dimensions of the block are 8.4 cm by 5.5 cm by 4.6 cm. From this data, what is the density of copper?

Example of Using Density in Conversion

• Density problems can be used to plug and chug in the formula

ORAs a conversion factor

ICE = .920 g ice 1 cm3 ice

What volume of silver metal will weigh exactly 2500.0 g. The density of silver is 10.5 g/cm3.

What is the weight of the ethyl alcohol that exactly fills a 200.0 mL container? The density of ethyl alcohol is 0.789 g/mL.

Antarctica has an ice sheet covering 1.42 x 1018 cm2 and averaging 1.61 x 105 cm deep. Calculate the total mass if ice has a density of 0.92 g/cm3.