Honors Chemistry

Honors Chemistry Measurement

Alchemy

How do you picture a chemist?

What is chemistry?Chemistry is the study of all things and the changes they can undergo.

Chemistry is called a central science because it overlaps so many sciences.

Chemical is any substance with a definite composition.Chemists use the scientific method as a systematic approach to gather knowledge.ObservationQuestionHypothesisExperimentConclusion

All hypotheses must be testable in order to be a valid hypothesis.Types of ObservationsQualitative: Describes something using the 5 senses

Quantitative: Uses numbers in the description

Quantity something that has magnitude, size, or amount.Unit a quantity adopted as a standard of measurementExperiment Natural Law Describes how nature behaves

Theory Explains why nature behaves the way it does

A theory and a hypothesis are both explanations, but a theory is an explanation formed after much experimentation.Variables in a ExperimentIndependent Variable - You control

Dependent Variable Variable factor what is being tested

Experimental Control Factor that remains constant for comparison Factors in an ExperimentIndependent: most regular variable goes on the X-axisDependent: what you are testing goes on the Y-axisExperimental Control: part of the experiment that stays the same.

Independent variable X axisDependent variable Y axisMeasurement in ChemistryMeasurement is a key ingredient in ALL sciences, especially chemistry.

Scientific NotationAccuracy and PrecisionSignificant FiguresMeasurement Devices Metric System Dimensional AnalysisScientific Notation is a shorthand way of expressing a number.

Consists of two factors: Coefficient - a number between 1 and 10 (only 1 digit to the LEFT of the decimal point)Base - a power of 10 power of 10 shows the number of 10s that are to be multiplied togetherExamples on the number line:1x1024x1011x1001x10-101x10-11x1001x10-101x10-1Large Numbers01x102NegativeNumbers4x101Small NumbersAdding and Subtracting(without calculator)Exponents must be the sameIf number gets bigger, exponent gets smallerIf number gets smaller, exponent gets larger

(8 x 10-2) + (3 x 10-4) - (2 x 10-3)(80 x 10-3) + (0.3 x 10-3) (2 x 10-3) = 78.3 x 10-3 = 7.83 x 10-2Multiplication (without calculator)Multiply number and add exponents (base 10 remains the same)

(6 x 10-6)(8 x 103) = 48 x 10-3 4.8 x 10-2(6 x 10-3)2 = 36 x 10-6 = 3.6 x 10-5Division (without calculator)Divide number and subtract exponents (base 10 remains the same)

(7.2 x 10-8)(8 x 10-5) = 0.9 x 10-3 9 x 10-4Cube RootMake number a whole number, take cube root of number, multiply exponent by 1/3.

(2.7 x 10-8)1/3 = (27 x 10-9)1/3 = 3 x 10-3Square RootMake number a whole number, take square root of number, multiply exponent by .

(1.44 x 10-6)1/2 = (144 x 10-8)1/2 = 12 x 10-4 = 1.2 x 10-3

Find the EE key it may be a 2nd function!Find the (-) key.If you have a graphing calculator look for the following keys:1st Commandment of Chemistry: KNOW THY CALCULATOR!

Find the Exp or x10xFind the (-) or the +/- key.Look at the calculator that is similar to yours1st Law of Chemistry: Know Thy Calculator!Uncertainty in MeasurementMeasurements are uncertain because:1) Instruments are not free from error.2) Measuring involves some estimation.

Precision when the instrument gives you about the same results under similar conditions. The smaller the increments of measurement an instrument has, the more precise it can be.

Accuracy when the experimental value is close to the actual value.

% Error = experimental accepted value x 100 accepted value

What is the goal for a game of darts? Hitting the Bulls Eye!Label the following data as accurate, precise, neither, or both.1) 200g, 1g, 40g Neither

2) 78g, 80g, 79gPrecise

3) 16g, 14g, 17gAccurate and PreciseHow to use a graduated cylinder

Read the meniscusHow to use a graduated cylinder

36.4 mL19.0 mL6.25 mL345345Length - Rulers3453.73.63.63Temperature

21.821.68How to read a triple beam balance

Ohaus Triple Beam Balance TutorialReading A Triple Beam Balance Tutorial28.570 gHow to read a triple beam balanceOhaus Triple Beam Balance TutorialReading A Triple Beam Balance Tutorial109.076 g

Significant Figures and DigitsA prescribed decimal that determines the amount of rounding off to be done base on the precision of the experiment.

ALWAYS ESTIMATE 1 DIGIT MORE THAN THE INSTRUMENT MEASURES.

Significant digits include measured digits and the estimated digit.

Exact Numbers Do not involve estimation ex. 12 in = 1 ft

VI. Significant DigitsUse Atlantic-Pacific Rule imagine a US map

bsentresentAtlanticPacificdecimalpointdecimalpoint

11001100.11.0100000.0250.000350002 significant digits4 significant digits8 significant digits2 significant digits5 significant digitsDecimal Absent Start counting with the 1st nonzero digit and count all the rest.Decimal Present Start counting with the 1st nonzero digit and count all the rest.1,000,1005 significant digitsSignificant Digits in Addition and SubtractionAdd or subtract numbers

Answer can only be as exact as the least exact number. (Look at the decimal place)

Ex. 4.1 cm + 0.07cm

4.17 cm

4.2 cmSignificant Digits and Multiplication and DivisionMultiply and Divide the numbers.

Round answer to the same number of significant digits as the number with the fewest significant digits.

Ex. 7.079 cm / 0.535 cm13.231775713.2Atmospheric pressure is measured with a barometer. This is a glass tube sealed at one end and filled with Hg.

Types of Manometers

Open Manometers

Using a Manometera device used to measure pressureReading a Manometer

Barometer containing Hg

Temperature ConversionsCelsius and Kelvin K = C + 273

C = K - 273

Zero Point on Kelvin Scale Absolute Zero 0 K and -273 C

Kinetic energy is energy of motion. Temperature is a measure of kinetic energy. Since the temperature at absolute zero is a true zero, there is no particle motion Therefore, nothing can exist at absolute zero. TEMPERATURE SCALES

Measurements: basic to all sciences & all are comparisons to a standardEnglish still used in US

Metric devised in the late 1700s in France

SI Le Systme Internationale dUnits Modern metric system (1960)Based on 7 base unitsBase units are modified by prefixesSI Base UnitsLengthMass (SI standard unit)TimeTemperature Amount of a substance mole (mol)Electric current ampere (A)Luminous intensitycandela (cd)meter (m)kilogram (kg)second (s)Kelvin (K)

The MeterThe original standard for the meter was kept in a safe in France.The meter stick is a replica of that standard.A meter is made up of 100 centimeters and 1000 millimeters.Lasers are now used to determine the standard for a meter.

The GramMass is the amount of matter in an object.1 cm3 of water = 1 gram. The standard kilogram is kept under lock and key in Washington, DC and other cities around the world.

Metric Conversion

Derived UnitsArea: 2-DL x W (m2)

Volume: 3-DSolid - L x W x H (m3)Liquid or irregular shaped object - graduated cylinder (L or cm3)

Density mass/volume(kg/m3)45The LiterThe liter is 1000 mL10cm x 10cm x 10cm 1 liter = 1000 cm3 = 1 dm31 milliliter = 1 cm3 = 1 cc = 20 drops

=

PrefixAbbreviationMeaningScientific Notationmega-M1,000,0001 x 106kilo-k1,0001 x 103hecto-h1001 x 102deka-da101 x 101BASE UNIT(g, m, L)--------------1100deci-d0.11 x 10-1centi-c0.011 x 10-2milli-m0.0011 x 10-3micro-0.000 0011 x 10-6nano-n0.000 000 0011 x 10-9pico-p0.000 000 000 0011 x 10-12Length Relationships

Conversions between unitsFactor-label method or dimensional analysis based on using unit equalities

60 s = 1 min 60 s OR 1 min1 min 60 sExample 1: 3.6 x 104 s = ? days3.6 x 104 s1 min

60 s1 hr

60 min1 day

24 hr= 0.42 days = 4.2 x 10-1 days3.6 x 104 s1 min__________________60 s1 hr__________________60 min1 day__________________24 hrxxx=Example 2: 36 mm3 = ? cm336 mm3mm31000 mm31 cm336 mm31 cm10 mm1 cm1 cm10 mm10 mm= 0.036 cm3Example 3: A room measures 12 feet by 15 feet. Calculate the minimum number of square yards of carpet needed to cover this area.180 ft29 ft21 yd2= 20 yd2A closer look at densityPhysical = A characteristic of a substance that does not involve a chemical change

Examples: texture, state of matter, density, hardness, boiling point

Density = The ratio of the mass of a substance to the volume of the substance.

D = mass / volume Density Column

Density

Which is more dense: Diet or Regular Soda?

Density of an Irregular solid:

1- Find the mass of the object2- Find the volume if the object by water displacement!

The characteristic plot for a Direct Relationship is a straight line graph. Indirect RelationshipThe characteristic plot for an Inverse Relationship is a curve of the type illustrated here. As one of the variables increases, the other decreases. Note: It is not a straight line sloping downward.

Use the following data to determine the density of aluminum.Determine the density of aluminum from the analysis of data from 5 samples.54.0-g sample has a volume of 20.0 mL14.0-g sample has a volume of 5.0 mL41.0-g sample has a volume of 15.0 mL27.0-g sample has a volume of 10.0 mL19.0-g sample has a volume of 7.0 mL

HINT: Graph the data with volume as the independent variable.The slope of the line is the density. Reminders: 1) Label both the x and y axis2) Give your graph a descriptive title3) Make a BEST FIT line/curve4) Show work for slope on graphDensity Graph

BACKEnergy TransferHeat-energy that is transferred from one object to another due to a difference in temperature. (symbol for heat = q)

Temperature = a measure of the average kinetic energy of the particles in a substance. Temperature is an intensive property, and heat is an extensive property.

Thermochemistry the study of heat changes in a chemical reaction.

Heat vs. TemperatureCalorimetryCalorimetry is the study of heat flow and measurement.

Calorimetry experiments determine the heats of reactions by making accurate measurements of temperature changes produced by a calorimeter.Calorimeter

Calorimeter

Heat Capacity amount of heat needed to raise the temperature of an object 1C.

Specific Heat amount of heat needed to raise 1g of a substance 1C.-Symbol for specific heat is C.

Heat and TemperatureFormula for heat absorbed for released:q = C x m x T

Remember: Specific Heat of Water = 4.184 J/g C

Chart354144127190

Volume (mL)Mass (g)Density of Aluminum

Sheet1VolumeMass20545141541102771900

Sheet1

Volume (mL)Mass (g)Density of Aluminum

Sheet2

Sheet3