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Chem 210 1/26/ Notes Ch 1 Essential Ideas The Study Of Chemistry Chemistry: Is the study of matter and the changes that matter undergoes. Matter: Is anything that has mass and occupies space. The Scientific Method ● Observation: Natural Phenomena and measured events; if universally consistent, can be stated as a law. ● Hypothesis: Tentative explanation that explains observations. ● Experiment: Procedure to test hypothesis; measures one variable at a time. ❖ Extra Notes: Hypothesis revised if experimental results do not support it. ● Theory: Set of conceptual assumptions that explains data from accumulated experiments; predicts related phenomena. ● Further Experiment: Tests predictions based on theory. ❖ Extra Notes: Model altered if experimental results do not support it. ❖ A theory can become a law.
Chem 210 1/26/
Classification Of Matter
solid, liquid and gas are the three states of matter commonly found on earth. A substance can convert from one state to another without changing the identity of the substance. ● Solid: Rigid and do not conform to the shape of their container. ● Liquid: Conform to the shape of their container. ● Gases: Assume both the shape and volume of their container.
Atoms
● Atoms: Smallest indivisible unit for an element. ● Molecule: Consists of 2 or more atoms joined by chemical bonds. ● Law of conservation of mass: No detectable change in mass during an ordinary chemical reaction. ● Law of definite proportions: A chemical compound always contains the same elements in the same proportions by mass. ❖ Aspirin will always have 9 carbon, 8 hydrogen, and 4 oxygen atoms (C9H8O4) ● Mixture: This can be separated by physical means its components without changing the identities of the components.
Chem 210 1/26/
The Properties Of Matter
The are two general types of properties of matter: ● Qualitative Properties: Are measured and expressed with a number. ● Qualitative Properties: Do not require measurement and are usually based on observation. ● Physical Property: Is one that can be observed and measured without changing the identity of the substance. ❖ color, melting point, boiling point, density ● Physical Change: Is one in which the state of matter changes, but the identity of the matter does not change. ❖ changes of state (melting, freezing, condensation) ● Physical Processes: Mixtures are separated , but the identities of the matter does not change. ● Chemical Property: Is one a substance exhibits as it interacts with another substance. ● Chemical Change: Is one that results in a change of composition; the original substances no longer exist. ● Extensive Property: Depends on the amount of matter. ● Intensive Property: Does not depend on the amount of matter. ● Quantitative Properties: A measured quantity must always include a unit. ● English System: Has units such as the foot, gallon, pound, etc. ● Metric System: Includes units such as the meter, liter, kilogram, etc.
SI Base Units
The magnitude of a unit may be tailored to an application using prefixes Prefix Symbol Meaning Example (base unit grams) Prefix Symbol Meaning Example (base unit grams) Tera– T 1 x 10^12 1 Tg = 1 x 10^12 g Giga– G 1 x 10^9 1 Gg = 1 x 10^9 g Mega– M 1 x 10^6 1 Mg = 1 x 1^06 g Kilo– k 1 x 10^3 1 kg = 1 x 10^3 g Hecto– h 1 x 10^2 1 hg = 1 x 10^2 g Deka– DA 1 x 10^1 1 dag = 1 x 10^1 g
Chem 210 1/26/ Unit (g, L, etc.) 1 g = 1 g Deci– d 1 x 10^-1 1 dg = 1 x 10^-1 g Centi– c 1 x 10^-2 1 cg = 1 x 10^-2 g Milli– m 1 x 10^-3 1 mg = 1 x 10^-3 g Micro– μ 1 x 10^-6 1 μg = 1 x 10^-6 g Nano– n 1 x 10^-9 1 ng = 1 x 10^-9 g Pico– p 1 x 10^-12 1 pg = 1 x 10^-12 g The great mighty king hector died unexpectedly drinking chocolate milk many nights past.
Conversion Factors
Notes: Conversion Factor is a fraction in which the same quantity is expressed one way in the numerator and another way in the denominator. Created from an equality statement (shows the relationship between two units. When we multiply by a conversion factor, we are only multiplying by 1, so nothing is changed! Equality Statement: 1hour=60minutes Conversion Factors: 1hour=60minutes/60minutes=1 hour
Mass
● Mass is a measure of the amount of matter in an object or sample. ❖ Because gravity varies from location to location, the weight of an object varies depending on where it is measured. But mass doesn’t change. ❖ The SI base unit of mass is the kilogram (kg), but in chemistry the smaller gram (g) is often used. ● Atomic mass unit (amu) is used to express the masses of atoms and other similar sized objects.
Chem 210 1/26/ significant if a decimal is present Zeros to the right of the last nonzero digit in a number that does not contain a decimal point may or may not be significant 100 1, 2, or 3 – ambiguous In addition and subtraction, the answer cannot have more digits to the right of the decimal point than any of the original numbers. In multiplication and division, the number of significant figures in the final product or quotient is determined by the original number that has the smallest number of significant figures. Exact numbers can be considered to have an infinite number of significant figures and do not limit the number of significant figures in a result. ● Accuracy tells us how close a measurement is to the true value. ● Precision tells us how close a series of replicate measurements are to one another ● Conversion Factor: is a fraction in which the same quantity is expressed one way in the numerator and another way in the denominator. Math for Chapter 1 in Chemistry 210: ● Sig Fig determine calculation ● Add^n and Subtract^n means lowest decimal place ● Multiply^n and Divide^n means lowest S.F. ● PLUS Rule Final Answer Standard: 2.439627. =2.4 or in this case =2.4x10^6= down others numbers^big number ● 6 place left 0.000002439627 = 2.4x10^-6=down other number^small number ● 6 place right Rounding numbers - Cometric Fixture Do not round up/down in the steps R up = 2439627 drop 2 and 7 6+1= 2439627 - 2439700 Value should remain If dropped number <5 - As is 2479600 If dropped number 5&>5 - Rup Left handside up
