International System Of Units (Metric System)

Types of Measurements 1- QUALITATIVE MEASUREMENTS: observations of reactions — changes in color and physical state. 2- QUANTITATIVE MEASUREMENTS: which involve numbers. –Use SI units — based on the metric system

What is Scientific Notation? Scientific notation is a way of expressing really big numbers or really small numbers.Scientific notation is a way of expressing really big numbers or really small numbers. For very large and very small numbers, scientific notation is more concise.For very large and very small numbers, 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  10 8 m/s in scientific notation. The same is true of small measurements. For example, the quantity kg can be written as 1.5  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 10 2  (move decimal 2 spots right) –4.285 x  (decimal moves 4 spots left) Converting From Scientific to Standard Notation

Learning Check Express these numbers in Scientific Notation:Express these numbers in Scientific Notation: 1) ) ) ) 2 5)

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 Prefixes Kilo- means 1000 of that unitKilo- means 1000 of that unit –1 kilometer (km) = 1000 meters (m) Centi- means 1/100 of that unitCenti- means 1/100 of that unit –1 meter (m) = 100 centimeters (cm) –1 dollar = 100 cents Milli- means 1/1000 of that unitMilli- means 1/1000 of that unit –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 = Kg

Symbolprefix 1,000,000,000,000,000, Eexa 1,000,000,000,000, Ppeta 1,000,000,000, Ttera 1,000,000, Ggiga 1,000, Mmega 1, Kkilo hhecto dadeka ddeci ccenti mmilli 0.000, µmicro 0.000,000, nnano 0.000,000,000, ppico 0.000,000,000,000, ffemto 0.000,000,000,000,000, aatto

Metric 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 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 meter1 nanometer (nm) = 1.0 x meter O—H distance = 9.4 x m 9.4 x cm nm O—H distance = 9.4 x m 9.4 x cm 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 Volume The 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 cm 3 = 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.

DENSITY - an important and useful physical property Mercury 13.6 g/cm g/cm 3 Aluminum 2.7 g/cm 3 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/cm 3 ). Sp.Gr. =Density of substance (g/ml) / Density of water (g/ml) PROBLEM: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 95 mL of Hg? Specific Gravity:

Learning Check If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given? 1) L 2) 1.25 L 3) 1.83 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 temperature There is three common scales used to determines temperature 1- Fahrenheit 2- Kelvin 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 kelvins (K), and the boiling point is K. The zero point on the Kelvin scale, 0 K, or absolute zero, is equal to  °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 Check The normal temperature of a chickadee is 105.8°F. What is that temperature in °C? The normal temperature of a chickadee is 105.8°F. What is that temperature in °C? 1) 73.8 °C 2) 58.8 °C 3) 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, X (in scientific notation) 1 dozen Al atoms = 12 Al atoms 1 mole of Al atoms = 6.02 X atoms A mole is Avogadro’s number of particles, that is 6.02 × particles. 1 mol = Avogadro’s Number = 6.02 × units

= 6.02 x C atom = 6.02 x H 2 O molecules = 6.02 x NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 6.02 x Na + ions and 6.02 x Cl – ions A Mole of Particles Contains 6.02 x particles 1 mole C 1 mole H 2 O 1 mole NaCl

6.02 x particles 1 mole or 1 mole 6.02 x 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 mol Na? –Step 1: we want atoms of Na –Step 2: we have mol Na –Step 3: 1 mole Na = 6.02 × atoms Na = 7.22 × atoms Na mol Na × 1 mol Na 6.02 × atoms Na

Mole Calculations I How many moles of potassium are in 1.25 × atoms K? –Step 1: we want moles K –Step 2: we have 1.25 × atoms K –Step 3: 1 mole K = 6.02 × atoms K = 2.08 × mol K1.25 × atoms K × 1 mol K 6.02 × 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 amu. Therefore, the molar mass of iron is 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 CaCl 2 –Avg. Atomic mass of Calcium = 40.08g –Avg. Atomic mass of Chlorine = 35.45g –Molar Mass of calcium chloride = g/mol Ca + (2 X 35.45) g/mol Cl  g/mol CaCl 2 20 Ca 40.08a 17 Cl Cl

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 × 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 mass g = mol x g/mol mol = g  g/mol This can be represented in an “ equation triangle ” g= g/mol x mol 0.25HCl H 2 SO NaCl 1.27CuEquation mol (n) gg/molFormula g molg/mol

Flowchart Atoms or Molecules Moles Mass (grams) Divide by 6.02 X Multiply by 6.02 X 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 = g Ti = 63.7 g Ti 1.33 mole Ti × g Ti 1 mole Ti

Mole Calculations II What is the mass of 2.55 × 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 × atoms Pb × 1 mol Pb 6.02×10 23 atoms Pb g Pb 1 mole Pb ×

Mole Calculations II How many O 2 molecules are present in g of oxygen gas? We want molecules O 2, we have grams O 2. Use Avogadro ’ s number and the molar mass of O × molecules O g O 2 × 1 mol O g O ×10 23 molecules O 2 1 mole O 2 ×

QUETTIONS ???