Chemistry: Chapter 1 - Introduction

Chemistry:- Is the science of the composition, structure, properties and reactions of matter, especially of atomic and molecular systems.-Is the science dealing with the compositions of matter and the changes in composition it undergoes. -It is considered with the composition and changes in the composition of matter and also with the energy and energy changes associated with matter. 

-Importance of Chemistry:  Learning about the composition of the world around us can lead to interesting and useful inventions and new technology. Chemistry is central to understanding many fields, including agriculture, astronomy, animal science, geology, medicine, molecular biology and material science. Chemistry is used by each of us everyday in our struggle to cope with our technological world. Learning about the benefits risks associated with chemicals will help you to be an informed citizen, able to make intelligent choices concerning the world around you. Studying Chemistry teaches you to solve problems and communicate with others in an organized and logical manner.

Scientific Method:-Is the general process whereby scientific knowledge grows. Steps in Scientific Method Asking questions. Performing background research. Constructing a hypothesis. Testing the hypothesis by conducting an experiment. Analyzing the data of the experiment to deduce a conclusion. Communicating the results. Generalization/Conclusions.

Definitions of Terms: Hypothesis:-Is a tentative explanation of certain facts that provides basis for further experimentation.Theory or Model:- Is a well-established hypothesis.-Is an explanation of the general principles of certain phenomena with considerable evidence or facts to support it.Scientific Laws:-Are simple statements of natural phenomena to which no exceptions are known under the given conditions.

  Standards For Measurement: Units of Measurement: (Quantitative Observation) Two Parts:   1. Number   2. Units        A measurement is expressed by a numerical value together with a unit of that measurement.              Ex. 70.0 kilograms = 154 lbs.                 Number obtained from a measurement are never exact values. They always have some degree of uncertainty due to limitations of the measuring instrument and the skill of the individual making the instrument.  The numerical value recorded for a measurement should give some indication of its reliability (precision).Precision:-Refers to the degree of agreement among several measurements of the same quantity.Accuracy:-Refers to the agreement of a particular value with the true value.Significant Figures:-Are those digits in the measured number that include all certain digit plus a final one that is somewhat uncertain.Guidelines for Using Significant Figures:    1. Any digit that is not zero is significant.                 845 = 3 s.f.                            1.234 = 4 s.f.     2. Zeros between nonzero digits are significant.                606 = 3 s.f.                            40,501 = 5 s.f.    3. Zeros to the left of the first non-zero digit are not significant.                 0.08 = 1 s.f.                           0.00000349 = 3 s.f.    4. If a number is greater than 1, then all zeros to the right of the decimal point is counted as significant figures.                2.0 = 2 s.f.                             3.040 = 4 s.f.*- If a number is less than 1, then only zeros that are the end of the number and the zeros that are between nonzero digits are significant.                0.090 = 2 s/f                        0.3005 = 4 s.f.       5. For numbers that do not contain trailing zeros may or may not be significant.                                    400 --------------- 4 x 10^2 = 1 s.f.                                                                       4.0 x 10 ^2 = 2 s.f.                                                                       4.00 x 10^2 = 3 s.f.Significant Figures in Calculations:    1. When multiplying or dividing the quantities, give as many significant figures in the answer as there are in the quantity with the fewest number of significant figures.    2. When adding or subtracting quantities, give the same number of the decimal places in the answer as there are in the quantity with the fewest number of decimal places.  

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