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CHEMISTRY 1211 Chapter 1. CHEMISTRY WHAT IS IT?. SCIENCE DEALING WITH THE COMPOSITION AND ENERGY OF MATTER AND THE CHANGES IN COMPOSITION AND ENERGY THAT MATTER UNDERGOES. WHAT IS A SCIENCE?. SCIENCE AN ORGANIZED BODY OF KNOWLEDGE. Scientific Method:.
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CHEMISTRYWHAT IS IT? SCIENCE DEALING WITH THE COMPOSITION AND ENERGY OF MATTER AND THE CHANGES IN COMPOSITION AND ENERGY THAT MATTER UNDERGOES.
WHAT IS A SCIENCE? SCIENCE AN ORGANIZED BODY OF KNOWLEDGE
Scientific Method: A systematic approach to solving problems.
WHAT IS MATTER? MATTER ANYTHING THAT HAS MASS AND OCCUPIES SPACE
Matter • Atoms are the building blocks of matter. • Each element is made of the same kind of atom.
MATTER PURE SUBSTANCES OR MIXTURES
PURE SUBSTANCES • DISTINCT PROPERTIES • CONSTANT COMPOSITION • TWO TYPES: • ELEMENTS • COMPOUNDS
PURE SUBSTANCES • ELEMENT: SUBSTANCE CONTAINING ONLY ONE TYPE OF ATOM
ATOM THE SMALLEST REPRESENTATIVE PARTICLE OF AN ELEMENT
PURE SUBSTANCES • COMPOUND: SUBSTANCE CONTAINING TWO OR MORE TYPES OF ATOMS IN A FIXED RATIO
MIXTURES • CONTAINS TWO OR MORE DIFFERENT SUBSTANCES • TWO TYPES • HETEROGENEOUS • HOMOGENEOUS
HETEROGENEOUS SUBSTANCES ARE VISUALLY DISTINGUISHABLE HOMOGENEOUS SUBSTANCES ARE VISUALLY INDISTINGUISHABLE
PROPERTIES OF MATTER • PHYSICAL PROPERTIES vs CHEMICAL PROPERTIES • INTENSIVE PROPERTIES vs EXTENSIVE PROPERTIES
PHYSICAL vs CHEMICAL PROPERTIES • PHYSICAL PROPERTIES CAN BE MEASURED WITHOUT CHANGING THE IDENTITY OR COMPOSITION • CHEMICAL PROPERTIES DESCRIBE THE WAY A SUBSTANCE CHANGES OR REACTS TO FORM OTHER SUBSTANCES
INTENSIVE vs EXTENSIVE PROPERTIES • INTENSIVE – NOT DEPENDENT ON THE AMOUNT OF SUBSTANCE PRESENT (TEMPERATURE, DENSITY, COLOR, MELTING POINT, BOILING POINT, ETC.) • EXTENSIVE – DEPENDS ON AMOUNT OF SUBSTANCE PRESENT (MASS AND VOLUME)
UNITS OF MEASUREMENTTHE SI SYSTEM • LENGTH - METER (m) • VOLUME - LITER (L) • TIME - SECOND (s) • MASS - KILOGRAM (kg) • TEMPERATURE - KELVIN (K)
TEMPERATURE K = oC + 273.15 AND oC = 5/9 (oF - 32) OR oF = 9/5 (oC) + 32
SIGNIFICANT FIGURES aka SIG FIGS aka SF
SIGNIFICANT FIGURES • IN COUNTING AND DEFINITIONS, THERE ARE AN INFINITE NUMBER OF SIG FIGS • IN MEASUREMENTS, THE NUMBER OF SIG FIGS CONSISTS OF ALL CERTAIN AND THE FIRST UNCERTAIN DIGITS
RULES FOR READING/RECORDING MEASURED VALUES • LEADING ZEROS ARE NEVER SIGNIFICANT • CAPTIVE ZEROS ARE ALWAYS SIGNIFICANT • TRAILING ZEROS ARE SIGNIFICANT ONLY IF A DECIMAL IS PRESENT
ROUNDING RULES LOOK ONLY AT NUMBER JUST TO RIGHT OF NUMBER YOU ARE ROUNDING TO: • IF 5 OR MORE, ROUND UP • IF LESS THAN 5, ROUND DOWN
MATH OPERATIONS INVOLVING SIGNIFICANT FIGURES • MULTIPLICATION / DIVISION: ANSWER WILL HAVE SAME TOTAL # OF SIG FIGS AS THE NUMBER WITH THE LEAST TOTAL # OF SIG FIGS • ADDITION / SUBTRACTION: ANSWER HAS SAME # OF DIGITS AFTER DECIMAL AS THE NUMBER WITH THE LEAST # OF DIGITS AFTER THE DECIMAL
GENERAL RULE CARRY ALL FIGURES THROUGH TO THE END OF A PROBLEM. ROUND THE FINAL ANSWER TO THE CORRECT NUMBER OF SIGNIFICANT FIGURES.
Accuracy versus Precision • Accuracy refers to the proximity of a measurement to the true value of a quantity. • Precision refers to the proximity of several measurements to each other.
DENSITY DENSITY IS AN INTENSIVE PROPERTY OF MATTER. THEREFORE, DENSITY IS INDEPENDENT OF HOW MUCH SAMPLE IS PRESENT
DENSITY DENSITY IS DEFINED AS THE MASS PER UNIT VOLUME OF A SUBSTANCE D = m/V USUALLY IN UNITS OF: g/mL or g/cm3