International System Of Units(Metric System)

Types of MeasurementsTypes of Measurements

1- 1- QUALITATIVE MEASUREMENTS:QUALITATIVE MEASUREMENTS: observations of reactions — changes in observations of reactions — changes in color and physical state.color and physical state.

2- QUANTITATIVE MEASUREMENTS2- QUANTITATIVE MEASUREMENTS: : which involve which involve numbersnumbers..

– UseUse SI unitsSI units — based on the metric — based on the metric systemsystem

What is Scientific Notation?What is Scientific Notation?

• Scientific notation is a way of expressing Scientific notation is a way of expressing really big numbers or really small numbers.really big numbers or really small numbers.

• For very large and very small numbers, For very large and very small numbers, scientific notation is more concise.scientific notation is more concise.

Writing Numbers in Scientific Notation

• Scientific notation is a method of expressing a quantity as a number multiplied by 10 to the appropriate power.

• For example, the measurement 300,000,000 m/s can be written as 3.0 108 m/s in scientific notation.

• The same is true of small measurements. For example, the quantity 0.0015 kg can be written as 1.5 10-3 in scientific notation.

• Move decimal point• # of spaces the decimal moves is the power of 10• If exponent is positive, move decimal to the right• If exponent is negative, move decimal to the left

– 4.285 x 102 428.5(move decimal 2 spots right)

– 4.285 x 10-4 0.0004285(decimal moves 4 spots left)

Converting From Scientific to Standard NotationConverting From Scientific to Standard Notation

Learning Check

• Express these numbers in Scientific Express these numbers in Scientific Notation:Notation:

1)1) 405789405789

2)2) 0.0038720.003872

3)3) 30000000003000000000

4)4) 22

5)5) 0.4782600.478260

The International System• To avoid confusion, scientists established the International System

of Units, or SI, in 1960 as the accepted system for measurement.

• There is Seven SI base units

Metric PrefixesMetric Prefixes• Kilo-Kilo- means 1000 of that unit means 1000 of that unit

– 1 kilometer (km) = 1000 meters (m)1 kilometer (km) = 1000 meters (m)

• Centi-Centi- means 1/100 of that unit means 1/100 of that unit

– 1 meter (m) = 100 centimeters (cm)1 meter (m) = 100 centimeters (cm)

– 1 dollar = 100 cents1 dollar = 100 cents

• Milli-Milli- means 1/1000 of that unit means 1/1000 of that unit

– 1 Liter (L) = 1000 milliliters (mL)1 Liter (L) = 1000 milliliters (mL)

• To convert a larger units to smaller units : multiply • Ex: 8Kg = 8 * 1000 = 8000g

• To convert a smaller units to larger units : divide

• Ex: 7g = 7/1000 = 0.007 Kg

prefixprefix SymbolSymbol

exaexa EE 10101818 1,000,000,000,000,000,0001,000,000,000,000,000,000

petapeta PP 10101515 1,000,000,000,000,0001,000,000,000,000,000

teratera TT 10101212 1,000,000,000,0001,000,000,000,000

gigagiga GG 101099 1,000,000,0001,000,000,000

megamega MM 101066 1,000,0001,000,000

kilokilo KK 101033 1,0001,000

hectohecto hh 101022 100100

dekadeka dada 101011 1010

decideci dd 1010-1-1 0.10.1

centicenti cc 1010-2-2 0.010.01

millimilli mm 1010-3-3 0.0010.001

micromicro µµ 1010-6-6 0.000,0010.000,001

nanonano nn 1010-9-9 0.000,000,0010.000,000,001

picopico pp 10-10-1212 0.000,000,000,0010.000,000,000,001

femtofemto ff 10-10-1515 0.000,000,000,000,0010.000,000,000,000,001

attoatto aa 10-10-1818 0.000,000,000,000,000,0010.000,000,000,000,000,001

Metric PrefixesMetric Prefixes

Length• Length is defined as the distance between two

points.

• The meter (m) is the SI unit of length. Smaller objects can be measured in centimeters (cm) or millimeters (mm). The length of your textbook or pencil would be measured in centimeters.

• To measure long distances, you use kilometers.

• Kilometers might be most familiar to you as the distance traveled in a car or the measure of a long-distance race.

Units of LengthUnits of Length• ? kilometer (km) = 500 meters (m)? kilometer (km) = 500 meters (m)

• 2.5 meter (m) = ? centimeters (cm)2.5 meter (m) = ? centimeters (cm)

• 1 centimeter (cm) = ? millimeter (mm)1 centimeter (cm) = ? millimeter (mm)

• 1 nanometer (nm) = 1.0 x 101 nanometer (nm) = 1.0 x 10-9-9 meter meter

O—H distance =O—H distance =9.4 x 109.4 x 10-11 -11 mm9.4 x 109.4 x 10-9 -9 cmcm0.094 nm0.094 nm

O—H distance =O—H distance =9.4 x 109.4 x 10-11 -11 mm9.4 x 109.4 x 10-9 -9 cmcm0.094 nm0.094 nm

Volume•Volume is the amount of space that something occupies. The volume of liquids are usually given in liters (L) or milliliters (mL). The volume of solids can be given in cubic meters (m3), cubic centimeters (cm3), or cubic millimeters (mm3).

•Units of VolumeThe SI unit of volume is the amount of space occupied by a cube that is 1 m along each edge. This volume is the cubic meter (m)3. A more convenient unit of volume for everyday use is the liter, a non-SI unit.

A liter (L) is the volume of a cube that is 10 centimeters (10 cm) along each edge (10 cm 10 cm 10 cm = 1000 cm3 = 1 L).

Common metric units of volume include the liter, milliliter, cubic centimeter, and microliter.

The volume of 20 drops of liquid from a medicine dropper is approximately 1 mL.

Mass

• The mass of an object measures the amount of matter in the object.

• The kilogram (kg) is the SI unit for mass. • You can determine mass with a triple-

beam balance. • The balance compares an object to a known

mass. Weight and mass are not the same. Mass depends only on the amount of matter in an object.

Weight

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

• The SI unit for weight is the Newton (N). • Weight depends on gravity, which can change

depending on where the object is located.

• If you were to travel to other planets, your weight would change, even though you would still be the same size and have the same mass.

• This is because gravitational force is different on each planet.

DENSITYDENSITY - an important and - an important and useful physical propertyuseful 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

• Density is the amount of matter in a given volume. Density can be expressed in grams per milliliter (g/mL) or grams per cubic centimeter (g/cm3).

Sp.Gr. =Density of substance (g/ml) / Density of water (g/ml)Sp.Gr. =Density of substance (g/ml) / Density of water (g/ml)

PROBLEM: Mercury (Hg) has a density of PROBLEM: Mercury (Hg) has a density of 13.6 g/cm13.6 g/cm33. What is the mass of 95 mL of Hg?. What is the mass of 95 mL of Hg?PROBLEM: Mercury (Hg) has a density of PROBLEM: Mercury (Hg) has a density of 13.6 g/cm13.6 g/cm33. What is the mass of 95 mL of Hg?. What is the mass of 95 mL of Hg?

95 cm3 • 13.6 g

cm3 = 1.3 x 103 g

• Specific Gravity:

Learning CheckLearning Check

If blood has a density of 1.05 g/mL, how many If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are liters of blood are donated if 575 g of blood are given?given?

1) 1) 0.548 L0.548 L

2) 2) 1.25 L1.25 L

3) 3) 1.83 L1.83 L

Temperature• The physical property of temperature is related to

how hot or cold an object is.

• Thermometers are used to measure temperature.

• Temperature is measured in SI with the Kelvin (K) scale.

• There is three common scales used to determines There is three common scales used to determines temperature temperature

1- Fahrenheit1- Fahrenheit2- Kelvin2- Kelvin3- Celcius 3- Celcius

Temperature Scales

• On the Celsius scale, the freezing point of water is 0°C and the boiling point is 100°C.

• On the Kelvin scale, the freezing point of water is 273.15 kelvins (K), and the boiling point is 373.15 K.

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

• The Kelvin scale starts at 0 K. In theory, 0 K is the coldest temperature possible in nature.

• Because one degree on the Celsius scale is equivalent to one kelvin on the Kelvin scale, converting from one temperature to another is easy. You simply add or subtract 273, as shown in the following equations.

• Conversions Between the Celsius and Kelvin Scales

• Fahrenheit Formula

Ḟ = 9/5 ċ + 32

• Celsius Formula

ċ = 5/9 * ( Ḟ - 32)

Learning CheckLearning Check

The normal temperature of a chickadee is 105.8°F. What The normal temperature of a chickadee is 105.8°F. What is that temperature in °C?is that temperature in °C?

1) 73.8 °C 1) 73.8 °C

2) 58.8 °C2) 58.8 °C

3) 41.0 °C3) 41.0 °C

• Precision is a description of how close measurements are to each other.

Precision and Accuracy

• Suppose you measure the distance between your home and your school five times and determine the distance to be 2.7 km.

• Suppose a friend measured 2.7 km on two days, 2.8 km on two days, and 2.6 km on the fifth day.

• Because your measurements were closer to each other than your friend’s measurements, yours were more precise.

Accuracy - a measure of how close a measurement is to the true value of the quantity being measured.

Accuracy

Example: Evaluate whether the following are precise, accurate or both.

Accurate

Not Precise

Not Accurate

Precise

Accurate

Precise

What is a mole?• The mole, whose abbreviation is “mol”, is the SI base unit for

measuring amount of a pure substance.• A counting unit• Similar to a dozen, except instead of 12, it’s 602 billion trillion

602,000,000,000,000,000,000,000• 6.02 X 1023 (in scientific notation)

• 1 dozen Al atoms = 12 Al atoms• 1 mole of Al atoms = 6.02 X 1023 atoms

• A mole is Avogadro’s number of particles, that is 6.02 × 1023 particles.

1 mol = Avogadro’s Number = 6.02 × 1023 units

= 6.02 x 1023 C atom

= 6.02 x 1023 H2O molecules

=6.02 x 1023 NaCl “molecules”(technically, ionics are compounds not molecules

so they are called formula units)

6.02 x 1023 Na+ ions and

6.02 x 1023 Cl– ions

A Mole of Particles Contains 6.02 x 1023 particles

1 mole C

1 mole H2O

1 mole NaCl

6.02 x 1023 particles 1 mole

or

1 mole

6.02 x 1023 particles

Note that a particle could be an atom OR a molecule!

Avogadro’s Number as Conversion Factor

Mole Calculations I• How many sodium atoms are in 0.120 mol Na?

– Step 1: we want atoms of Na

– Step 2: we have 0.120 mol Na

– Step 3: 1 mole Na = 6.02 × 1023 atoms Na

= 7.22 × 1022 atoms Na0.120 mol Na ×1 mol Na

6.02 × 1023 atoms Na

Mole Calculations I• How many moles of potassium are in 1.25 × 1021

atoms K?

– Step 1: we want moles K

– Step 2: we have 1.25 × 1021 atoms K

– Step 3: 1 mole K = 6.02 × 1023 atoms K

= 2.08 × 10-3 mol K 1.25 × 1021 atoms K ×1 mol K

6.02 × 1023 atoms K

Periodic Table

• The atomic mass of any substance expressed in grams is

the molar mass (MM) of that substance.

• Equal to the numerical value of the average atomic

mass (get from periodic table)

1 mole of C atoms = 12.0 g

1 mole of Mg atoms = 24.3 g

1 mole of Cu atoms = 63.5 g

• The atomic mass of iron is 55.85 amu.

• Therefore, the molar mass of iron is 55.85 g/mol.

Molar Mass

Molar Mass of Compounds• The molar mass (MM) of a compound is determined

the same way, except now you add up all the atomic masses for the molecule (or compound)– Ex. Molar mass of CaCl2

– Avg. Atomic mass of Calcium = 40.08g– Avg. Atomic mass of Chlorine = 35.45g– Molar Mass of calcium chloride =

40.08 g/mol Ca + (2 X 35.45) g/mol Cl 110.98 g/mol CaCl2

20

Ca  40.08 17

Cl 35.45

Mole Calculations II

• Now we will use the molar mass of a compound to convert between grams of a substance and moles or particles of a substance.

6.02 × 1023 particles = 1 mol = molar mass

• If we want to convert particles to mass, we must first convert particles to moles and than we can convert moles to mass.

Converting between grams and moles• If we are given the # of grams of a compound

we can determine the # of moles, & vise-versa• In order to convert from one to the other you

must first calculate molar massg = mol x g/molmol = g g/mol

• This can be represented in an “equation triangle”

g= g/mol x molg= g/mol x mol0.250.25HClHCl

53.1553.15HH22SOSO44

3.553.55NaClNaCl1.271.27CuCu

EquationEquationmol (n)mol (n)ggg/molg/molFormulaFormula

g

mol

g/mol

FlowchartAtoms or Molecules

Moles

Mass (grams)

Divide by 6.02 X 1023

Multiply by 6.02 X 1023

Multiply by atomic/molar mass from periodic table

Divide by atomic/molar mass from periodic table

Mass-Mole Calculations

• What is the mass of 1.33 moles of titanium, Ti?

• We want grams, we have 1.33 moles of titanium.

• Use the molar mass of Ti: 1 mol Ti = 47.88 g Ti

= 63.7 g Ti1.33 mole Ti ×47.88 g Ti1 mole Ti

Mole Calculations II

• What is the mass of 2.55 × 1023 atoms of lead?

• We want grams, we have atoms of lead.

• Use Avogadro’s number and the molar mass of Pb

= 87.8 g Pb

2.55 × 1023 atoms Pb ×1 mol Pb

6.02×1023 atoms Pb

207.2 g Pb1 mole Pb

×

Mole Calculations II• How many O2 molecules are present in 0.470 g of

oxygen gas?

• We want molecules O2, we have grams O2.

• Use Avogadro’s number and the molar mass of O2

8.84 × 1021 molecules O2

0.470 g O2 ×1 mol O2

32.00 g O2

6.02×1023 molecules O2

1 mole O2

×

QUETTIONS???