types of observations and measurements we make qualitative observations – physical and chemical...
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Types of Observations and Types of Observations and MeasurementsMeasurements
• We makeWe make QUALITATIVEQUALITATIVE observations – physical and observations – physical and chemical properties and changeschemical properties and changes
• We also makeWe also make QUANTITATIVE QUANTITATIVE MEASUREMENTSMEASUREMENTS, which involve , which involve numbersnumbers..
–UseUse SI units SI units — based on the — based on the metric systemmetric system
SI measurementSI measurement• Le Système international Le Système international
d'unitésd'unités • Among countries with non-Among countries with non-
metric usage, the U.S. and metric usage, the U.S. and Bahrain are the only countries Bahrain are the only countries significantly holding outsignificantly holding out..
• The U.S. officially adopted SI in The U.S. officially adopted SI in 1866.1866.
Why should all scientists use the same Why should all scientists use the same measurement system/measurement system/
On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mars’ atmosphere 100 km lower than planned and was destroyed by heat.
1 lb = 1 N
1 lb = 4.45 N
Standards of MeasurementStandards of Measurement
When we measure, we use a measuring tool to When we measure, we use a measuring tool to compare some dimension of an object to a standard.compare some dimension of an object to a standard.
For example, at one time the For example, at one time the standard for length was the standard for length was the king’s foot. What are some king’s foot. What are some
problems with this standard?problems with this standard?
Stating a MeasurementStating a Measurement
In every measurement there is aIn every measurement there is a
Number Number followed by a followed by a
Unit Unit from a measuring devicefrom a measuring device
The number should also be as precise as the measurement!The number should also be as precise as the measurement!
UNITS OF UNITS OF MEASUREMENTMEASUREMENT
Use Use SI unitsSI units — based on the metric — based on the metric systemsystem
Length Length
MassMass
VolumeVolume
TimeTime
TemperatureTemperature
Meter, mMeter, m
Kilogram, kgKilogram, kg
Seconds, sSeconds, s
Celsius degrees, ˚CCelsius degrees, ˚Ckelvins, Kkelvins, K
Liter, LLiter, L
Mass vs. WeightMass vs. Weight
• Mass: Amount Mass: Amount of Matter (grams, of Matter (grams, measured with a measured with a BALANCE)BALANCE)
• Weight: Force Weight: Force exerted by exerted by gravity (Newton, gravity (Newton, measured with a measured with a SPRING SCALE)SPRING SCALE)
I weigh 0 N I weigh 0 N right nowright now
Some Tools for Some Tools for MeasurementMeasurement
Fluid Volume – Graduated Fluid Volume – Graduated Cylinder and BeakerCylinder and Beaker
Volume – Ruler/CalculatorVolume – Ruler/Calculator
Time – Stopwatch or ClockTime – Stopwatch or Clock
Mass – BalanceMass – Balance
Weight – Spring ScaleWeight – Spring Scale
Temperature – Temperature – ThermometerThermometer
Learning Check
Match Match L) lengthL) length M) mass M) mass V) volume V) volume
____ A. A bag of tomatoes is 4.6 kg.____ A. A bag of tomatoes is 4.6 kg.
____ B. A person is 2.0 m tall.____ B. A person is 2.0 m tall.
____ C. A medication contains 0.50 g Aspirin.____ C. A medication contains 0.50 g Aspirin.
____ D. A bottle contains 1.5 L of water.____ D. A bottle contains 1.5 L of water.
M
L
M
V
Metric PrefixesMetric Prefixes
Metric PrefixesMetric Prefixes
1. 1000 m = 1 1. 1000 m = 1 ______ a) mm b) km c) dma) mm b) km c) dm
2. 0.001 g = 1 2. 0.001 g = 1 ___ ___ a) mg b) kg c) dga) mg b) kg c) dg
3. 0.1 L = 1 3. 0.1 L = 1 ______ a) mL b) cL c) dLa) mL b) cL c) dL
4. 0.01 m = 1 ___ 4. 0.01 m = 1 ___ a) mm b) cm c) dma) mm b) cm c) dm
Learning Check
Learning Check
Select the unit you would use to measure Select the unit you would use to measure
1. Your height1. Your height
a) millimeters a) millimeters b) metersb) meters c) kilometers c) kilometers
2. Your mass2. Your mass
a) milligramsa) milligrams b) gramsb) grams c) kilograms c) kilograms
3. The distance between two cities3. The distance between two cities
a) millimetersa) millimeters b) metersb) meters c) kilometers c) kilometers
4. The width of an artery4. The width of an arterya) millimetersa) millimeters b) metersb) meters c) kilometers c) kilometers
Temperature ScalesTemperature Scales• FahrenheitFahrenheit
• CelsiusCelsius
• KelvinKelvin
Anders Celsius1701-1744
Lord Kelvin(William Thomson)1824-1907
Temperature ScalesTemperature Scales
Notice that 1 kelvin = 1 degree Celsius1 kelvin = 1 degree Celsius
Boiling point Boiling point of waterof water
Freezing point Freezing point of waterof water
CelsiusCelsius
100 ˚C100 ˚C
0 ˚C0 ˚C
100˚C100˚C
KelvinKelvin
373 K373 K
273 K273 K
100 K100 K
FahrenheitFahrenheit
32 ˚F32 ˚F
212 ˚F212 ˚F
180˚F180˚F
Calculations Calculations Using Using TemperatureTemperature
• Generally require temp’s in Generally require temp’s in kelvinskelvins
• T (K) = t (˚C) + 273.15T (K) = t (˚C) + 273.15
• Body temp = 37 ˚C + 273 = 310 KBody temp = 37 ˚C + 273 = 310 K
• Liquid nitrogen = -196 ˚C + 273 = 77 KLiquid nitrogen = -196 ˚C + 273 = 77 K
• Generally require temp’s in Generally require temp’s in kelvinskelvins
• T (K) = t (˚C) + 273.15T (K) = t (˚C) + 273.15
• Body temp = 37 ˚C + 273 = 310 KBody temp = 37 ˚C + 273 = 310 K
• Liquid nitrogen = -196 ˚C + 273 = 77 KLiquid nitrogen = -196 ˚C + 273 = 77 K
Reading a MeterstickReading a Meterstick
. l. l22. . . . I . . . . I. . . . I . . . . I33 . . . .I . . . . I . . . .I . . . . I44. . cm. . cm
First digit (known)First digit (known) = 2 = 2 2.?? cm2.?? cm
Second digit (known)Second digit (known) = 0.7 = 0.7 2.7? cm2.7? cm
Third digit (estimated) between 0.05- 0.07Third digit (estimated) between 0.05- 0.07
Length reportedLength reported == 2.75 cm 2.75 cm
oror 2.74 cm 2.74 cm
oror 2.76 cm2.76 cm
Learning CheckLearning Check
. l8. . . . I . . . . I9. . . .I . . . . I10. . cm
What is the length of the line?What is the length of the line?
1) 9.6 cm 1) 9.6 cm
2) 9.62 cm 2) 9.62 cm
3) 9.63 cm3) 9.63 cm
Fluid Volume
• Meniscus – curved area at top of fluid, caused by surface tension
–Read bottom of the curve to get an accurate measurement
Learning Check
Volume of a Regular Solid
• Volume = Length x Width x Height
Volume DisplacementVolume Displacement
Measure volume in mL before adding object.Measure volume in mL before adding object.
Gently slide object into cylinder and re-measure the volume.Gently slide object into cylinder and re-measure the volume.
Subtract the smaller number from the larger numberSubtract the smaller number from the larger number..
33 mL33 mL25 mL 25 mL
Triple Beam Balance
Measurements are in grams
100 + 40 +2142 grams
DENSITYDENSITY - an important - an important and useful physical propertyand useful physical property
Density mass (g)volume (cm3)
Density mass (g)volume (cm3)
Mercury
13.6 g/cm13.6 g/cm33 21.5 g/cm21.5 g/cm33
Aluminum
2.7 g/cm2.7 g/cm33
Platinum