General and Inorganic Chemistry Introduction to Chemistry.
Post on 18-Jan-2016
General and Inorganic ChemistryIntroduction to Chemistry
What is ChemistryChemistry is the study of chemicals; how properties depend on composition. What substances are and how they change.El Khemid - the transformation. Chemistry is about changing substances into others. What chemicals? First metals then cosmetics, medicines, ceramics, glass making.
What did early chemists do?Identify, classify, describe; Knowledge leads to curiosity. Rather than learn all substances seek underlying patterns and theories that explain chemical behavior. Apply scientific method.
Apply scientific method. Observation vs interpretationObservation - with statement of certainty is a factLaws - generalized observationsHypothesis to explain observations - predictionsExperiment - Test hypothesisTheory - tested hypothesisModel- Combination of theories that form a general explanation of wide variety of phenomenon
A Delicate BalanceScience is different from art in that scientific knowledge requires agreement; first of the facts and then of the theories.There is a delicate balance between what is known and what we think about what is known. This is the idea of provisional truth; we believe our hypotheses but maintain a healthy skepticism.
Serendipity"Chance favors the prepared mindWhen asked what did you think when you saw the bones of your hand on the screen in front of the cathode ray tube? Roentgen replied I did not think. I investigated.
How do we describe matter? Matter occupies space and has weight. (Actually Mass, weight is the affect of gravity on mass). Matter exists in three physical states.SolidLiquidGas
Properties of MatterPhysical properties: Color, mp, bp, density, index of refraction. Observation of these do not change chemical composition. Chemical properties: Observation of these causes a chemical change; substances become other substances. Reactivity with acids to liberate carbons dioxide.
Physical propertiesPhysical properties can be:Extensive i.e. depend on amount of substance like mass or volumeIntensive i.e. independent of amount like temperature or pressure.Some properties are qualitative others are quantitative.
Measurements require a system of unitsSI- Systeme InternationalBase units m, kg, s, K, mol Derived units: Joule, liter, pascalPrefixes: mega, kilo, deci, centi, milli, micro, nano, pico
PRIVATE1 in = 2.54 cm
1 m = 39.37 in
1 lb = 453.6 g
1 kg = 2.205 lb
1 qt = 946.4 mL
1 L = 1.057 qt
J = 1 kg m/s2
1 cal = 4.184 J
TF = 9/5 TC + 32
TK = TC + 273.15
EnergyEnergy: ability to do workKinetic = mv2/2Potential - chemicalConservation of energy. Heat and work transfer energy
Temperature: zeroeth law
Heat is the flow of energy from a hot object to a cold object.Heat flows from regions of high temperature to regions of low temperature.Differentiate between heat which is energy flow and temperature which gives the direction of flow.
Accuracy and Precision An Advil Tablet was "weighed" on a digital laboratory balance 22 times with the following results
The normal distributionmean= 0.4586
mean= 0.4586, Standard deviation
The normal distribution67%95%
PRIVATE1. All non - zero digits and captured zeros ARE SIGNIFICANT:
6023 has four significant figures.
2.Zeros used only to position the decimal point are NOT SIGNIFICANT:
0.0006023 has four significant figures.
3.If a result ends in zeros to the right of the decimal point
then those zeros ARE SIGNIFICANT. 2.200 has four significant figures.
4.If a result ends in zeros not to the right of the decimal point
these zero ARE NOT SIGNIFICANT. 600 000 has only one significant figure.
Every sample of a pure substance has the same properties. In contrast the properties of mixtures depend on the compostion of each sample
Mixtures can be separated into their pure componentsMixtures can be separated into their pure components by physical meansFiltrationMechanical separationDistilationDissolvingChromatography
Elements &CompoundsElements can not be broken down into simpler substancesCompounds can be chemically broken down into the elements of which they are composed.There are 108 elements known but 40 of these compose 99.9% of all substances.10 elements compose 99% of the earths crust.
Ten elements compose 99% of the earths crust
Three quarters of the elements are metalsMetals are:MalleableDuctileLustrousConductorsheatelectricityThe chemical symbols for some metals are not the same as the first letter of the English name for the element:Pb-leadW-tungstenK-potassiumCu-copperFe-ironHg-mercuryNa-sodiumSn-tin
These non-metals are solids at room temperature:Arsenic-AsPhosphorous-P Sulfur-SIodine-I Boron-BSelenium-Se Carbon-CThe rest are gases
The Law of Constant CompositionThe relative amounts of each element in a compound are always the same. Mass percentage or percent compositionMass of ElementMass of compoundX 100Fe = 1.56 gS= 0.9007g 2.47g% massFe = 1.56/2.47 x100 = 63.5%