Chemistry 111 Week 1 Science is the product of observations common sense rational thinking experimentation and sometimes brilliant insights o Children make the best scientists o Science often begins by asking a broad question To help answer this question the scientist undertakes various activities such as performing experiments o Scientists must document their thinking Scientific Process Hypothesis suggested explanation for observable phenomenon Scientific Hypothesis only after it can be tested through experiments only after it is tested and supported by experimental data over and over again without contradication Scientific Law or Principle a well tested hypothesis that unifies a broad range of observations within the natural world Scientific Theory Theories not fixed o Theories are a foundation of science but like facts hypotheses and laws they are o Rather they evolve as they go through stages of redefinition and refinement so as to mirror nature as accurately as possible o Atomic Theory is a great example of this refinement in chemistry Chemistry is the study of matter its composition properties and transformations i e changes o Matter anything that has mass and takes up space Changes physical and chemical 3 types of matter Solid Liquid Gas Plasma Page 1 Chemistry 111 Naturally occurring matter cotton sand digoxin a cardiac drug Synthetic human made matter nylon Styrofoam Ibuprofen Properties of matter o Boiling point o Melting point o Solubility o Color o Odor Physical Properties can be observed or measured without changing the composition of the material Physical Change alters the material without changing its composition o Melting ice solid water to form liquid water o Boiling liquid water to form steam gaseous water Chemical Properties determine how a substance can be converted into Chemical Change is the chemical reaction that converts one substance another substance into another o A piece of paper burning o Metabolizing an apple for energy o Oxygen and hydrogen combining to form water o Chemistry is the study of substances in terms of their Composition Structure Properties Reactions What is it made of How is it put together What characteristics does it have How does it behave with other substances o Chemistry happens when a car is started food is digested rust is formed on iron nails fertilizer is added to help plants grow electricity is produced from burning natural gas Measurements o Every measurement is composed of a number and a unit The number is meaningless without the unit Proper aspirin dosage 325 milligrams or pounds A fast time for the 100 meter dash 10 00 seconds or days Page 2 Chemistry 111 weight o The English System uses units like feet length gallons volume and pounds o The Metric System uses units like meters length liters volume and grams mass Each type of measurement has a base unit Other units are related to the base unit by a power of 10 The prefix of the unit name indicates if the unit is larger or smaller than the base unit Conversions 1 kilometer km 1 000 meters m 1 km 1 000 m 1 mm 0 001 m 1 millimeter mm 0 100 meters m OR 1 000 mm 1 m Page 3 Chemistry 111 1 centimeter cm 0 01 meters m OR 100 cm 1 m 1 cm 0 01 m REMEMBER o Millennium 1 000 years o Century 100 years Measuring Mass o Mass is a measure of the amount of matter in an object Weight is the force that matter feels due to gravity Conversions 1 kilogram kg 1 000 grams g 1 milligram mg 0 001 grams g 1 kg 1 000 g 1 mg 0 001 g Examples A 1 kilogram gold bar resting on the Earth weighs 2 2 pounds On the moon this same gold bar would weigh 0 37 pound Deep in space the gold bar would weigh 0 pounds but still have a mass of 1 kilogram Measuring Volume o 1 kiloliter kL 1 000 liters L 1 kL 1 000 L o 1 milliliter mL 0 001 liters L o Volume 1 mL 0 001 L Length X Width X Height cm x cm x cm Significant Figures 1 mL 1 cm3 1 cm cm or cc o Exact and Inexact Numbers 10 fingers 10 toes 1 meter 100 centimeters An Exact Number results from counting objects or is part of a definition An Inexact Number results from a measurement or observation and contains some uncertainty MEASURED 15 3 cm 1000 8 g 0 0034 mL Examples Measured gold melts at 1064 C Exact 1 yard 3 feet Measured the diameter of a red blood cell is 6 x 10 4 cm Exact there are 6 hats on the shelf Measured a can of soda contains 355 mL of soda Page 4 Chemistry 111 o Determining Significant figures Significant Figures are all the digits in a measured number including one estimated digit All nonzero digits are always significant 65 2 g 3 significant figures 255 345 g 6 significant figures The first digit 2 Plus the second digit 2 7 The markings on the meter stick at the end of the blue line are read as The last digit is obtained by estimating The end of the line might be estimated between 2 7 and 2 8 as 0 05 or 0 06 which gives a reported length of 2 75 cm or 2 76 cm If the length is reported as 2 76 cm The digits 2 and 7 are certain known The final digit 6 was estimated uncertain All three digits 2 76 are significant including the estimated digit o Why are significant figures important When reporting scientific data significant figures give the reader an idea of how accurately data has been measured i e gives info on error As number significant figures increases error decreases and the precision of the measuring device increases Example You measure the mass of lump of Fe on different balances o Triple Beam Balance 1 6 g 0 1 g Marked at every 1 g o Electronic Balance 1 597 g 0 001 g o Which measurement has less error o Rules to determine when a zero is a significant figure Rule 1 A zero counts as a significant figure when it occurs Between two nonzero digits Rule 2 A zero does not count as a significant figure when it occurs At the end of a number with a decimal place o 29 05 g o 1 0087 mL o 3 7500 cm o 620 lb 4 significant figures 5 significant figures 5 significant figures 3 significant figures At the beginning of a number o 0 00245 mg o 0 008 mL 3 significant figures 1 significant figure At the end of a number that does not have a decimal o 2570 m o 1245500 m 3 significant figures 5 significant figures o Significant figure rules for multiplication and division Page 5 Chemistry 111 The answer has the same number of significant figures as the original number with the fewest significant figures o Significant figure rules for rounding off numbers If the first digit to be dropped is between 0 and 4 then drop it and all …