3.2 Units of Measurement > 1 You may correct a low quiz score to an 85%. You have the option of writing an outline over the section(s) covered by the quiz

3.2 Units of Measurement >3.2 Units of Measurement >

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You may correct a low quiz score to an 85%. You have You may correct a low quiz score to an 85%. You have the option of writing an outline over the section(s) the option of writing an outline over the section(s) covered by the quiz. The maximum corrected score will covered by the quiz. The maximum corrected score will be an 85%.be an 85%.

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Section Outlines Section Outlines

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• Section Title• Main headings ( Red/Blue/green subtitles)

• Turn the main headings into questions

• Approximately 1-3 sentence per question (above)

• Must include –Key concepts, equations, variables

• Must include Examples • Graph, data table, example problem, diagram…


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Example p.62Example p.62

• 3.1 Using and expressing measurements• How can you use scientific notation?

• Measurements have both numbers and units; measurements can be written in scientific notation (3x103m or 3x10-3m)

• Numbers must be between 1 and 10; x10 to a power• The exponent is always a whole number• Positive = times 10 & negative = divided by 10

• How can you multiply and divide number written in scientific notation?


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Chapter 3Scientific Measurement

3.1 Using and Expressing Measurements

3.2 Units of Measurement

3.3 Solving Conversion Problems



Using SI Units

What makes metric units easy to use?

Using SI UnitsUsing SI Units



• The standards of measurement used in science are those of the metric system.

All metric units are based on multiples of 10. As a result, you can convert between units easily.




• The metric system was originally established in France in 1795.

• The International System of Units (abbreviated SI after the French name, Le Système International d’Unités) is a revised version of the metric system.

• The SI was adopted by international agreement in 1960.





• There are seven SI base units.

• From these base units, all other SI units of measurement can be derived.

• Derived units are used for measurements such as volume, density, and pressure.

SI Base Units

Quantity SI base unit

Symbol

Length meter m

Mass kilogram kg

Temperature kelvin K

Time second s

Amount of substance

mole mol

Luminous intensity

candela cd

Electric current

ampere A


9

prefixes you need to know.prefixes you need to know.


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How to use the previous chart to set up conversions How to use the previous chart to set up conversions for for metersmeters

• 1mm= 0.001m 1m=1,000 mm• 1cm= 0.01m 1m=100cm• 1dm= 0.1m1m=10dm• 1m= 1m 1m=1m• 1dam= 10m 1m=0.1dam• 1hm= 100m 1m=0.01hm• 1km= 1,000m 1m=0.001km




The table below lists the prefixes in common use.Units of Length

Commonly Used Metric Prefixes

Prefix Symbol Meaning Factor

mega M 1 million times larger than the unit it precedes 106

kilo k 1000 times larger than the unit it precedes 103

deci d 10 times smaller than the unit it precedes 10-1

centi c 100 times smaller than the unit it precedes 10-2

milli m 1000 times smaller than the unit it precedes 10-3

micro μ 1 million times smaller than the unit it precedes 10-6

nano n 1 billion times smaller than the unit it precedes 10-9

pico p 1 trillion times smaller than the unit it precedes 10-12



• For example, the prefix milli- means 1/1000 (one-thousandth), so a millimeter (mm) is 1/1000 of a meter, or 0.001 m.

• A hyphen (-) measures about 1 mm.

• For large distances, it is most appropriate to express measurements in kilometers (km).

• The prefix kilo- means 1000, so 1 km equals 1000 m.

Units of LengthUsing SI UnitsUsing SI Units



• The space occupied by any sample of matter is called its volume.

• You calculate the volume of any cubic or rectangular solid by multiplying its length by its width by its height.

• The unit for volume is thus derived from the units of length.

Units of Volume




These figures give you some idea of the relative sizes of a liter and a milliliter.

Units of Volume


1 mL

1 L



• The mass of an object is measured in comparison to a standard mass of 1 kilogram (kg), which is the basic SI unit of mass.

• A kilogram was originally defined as the mass of 1 L of liquid water at 4°C.

• A cube of water at 4°C measuring 10 cm on each edge would have a volume of 1 L and a mass of 1000 grams (g), or 1 kg.

• A gram (g) is 1/1000 of a kilogram; the mass of 1 cm3 of water at 4°C is 1 g.

Units of Mass




• Weight is a force that measures the pull on a given mass by gravity.

• Weight, a measure of force, is different from mass, which is a measure of the quantity of matter.

• The weight of an object can change with its location.

• An astronaut in orbit is weightless, but not massless.

Units of Mass




Temperature Scales

What temperature units do scientists commonly use?

Temperature ScalesTemperature Scales



• Temperature is a measure of how hot or cold an object is.

• An object’s temperature determines the direction of heat transfer.

• When two objects at different temperatures are in contact, heat moves from the object at the higher temperature to the object at the lower temperature.




Scientists commonly use two equivalent units of temperature, the degree Celsius and the kelvin.




• The figure below compares the Celsius and Kelvin scales.

• The zero point on the Kelvin scale, 0 K, or absolute zero, is equal to –273.15°C.


Celsius

Kelvin

100 divisions

100 divisions

100°CBoiling point

of water373.15 K

0°CFreezing point

of water273.15 K



Density

What determines the density of a substance?

DensityDensity



• The relationship between an object’s mass and its volume tells you whether it will float or sink.

• This relationship is called density.

• Density is the ratio of the mass of an object to its volume.

DensityDensity

massvolume

Density =



• When mass is measured in grams, and volume in cubic centimeters, density has units of grams per cubic centimeter (g/cm3).

• The SI unit of density is kilograms per cubic meter (kg/m3).

DensityDensity



This figure compares the density of four substances: lithium, water, aluminum, and lead.

DensityDensity

Increasing density (mass per unit volume)

10 g

0.53 g/cm3

19 cm3

10 g10 cm3

10 g3.7 cm3

10 g0.88 cm3

1.0 g/cm3 2.7 g/cm3 11 g/cm3



Density is an intensive property that depends only on the composition of a substance, not the size of the sample.

DensityDensity



Sample Problem 3.8Sample Problem 3.8

Calculating Density

A copper penny has a mass of 3.1 g and a volume of 0.35 cm3. What is the density of copper?




Analyze List the knowns and the unknown.

Use the known values and the equation for density to solve the problem.

KNOWNS mass = 3.1 gvolume = 0.35 cm3

UKNOWN density = ? g/cm3

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Density = mass volume

Calculate Solve for the unknown.

Start with the equation for density.

2



Calculate Solve for the unknown.

Substitute the known values for mass and volume and then calculate.


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Density =3.1 g

0.35 cm3= 8.8571 g/cm3 = 8.9 g/cm3

The calculated answer must be rounded to two significant figures.



All metric units are based on multiples of 10. As a result, you can convert between units easily.

Scientists commonly use two equivalent units of temperature, the degree Celsius and the kelvin.

Density is an intensive property that depends only on the composition of a substance.

Key ConceptsKey Concepts



K = °C + 273

°C = K – 273

Key EquationsKey Equations

Density = mass volume



• International System of Units (SI): the revised version of the metric system, adopted by international agreement in 1960

• meter (m): the base unit of length in SI

• liter (L): the volume of a cube measuring 10 centimeters on each edge (1000 cm3); it is the common unprefixed unit of volume in the metric system

• kilogram (kg): the mass of 1 L of water at 4°C; it is the base unit of mass in SI

• gram (g): a metric mass unit equal to the mass of 1 cm3

of water at 4°C

Glossary TermsGlossary Terms



• weight: a force that measures the pull of gravity on a given mass

• energy: the capacity for doing work or producing heat

• Joule (J): the SI unit of energy; 4.184 J equals one calorie

• calorie (cal): the quantity of heat needed to raise the temperature of 1 g of pure water 1°C

• temperature: a measure of the average kinetic energy of particles in matter; temperature determines the direction of heat transfer




• Celsius scale: the temperature scale in which the freezing point of water is 0°C and the boiling point is 100°C

• Kelvin scale: the temperature scale in which the freezing point of water is 273 K and the boiling point is 373 K; 0 K is absolute zero

• absolute zero: the zero point on the Kelvin temperature scale, equivalent to –273.15°C

• density: the ratio of the mass of an object to its volume




END OF 3.2END OF 3.2

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3.2 Units of Measurement > 1 You may correct a low quiz score to an 85%. You have the option of writing an outline over the section(s) covered by the quiz