Transcript document
Matter and Measurement Review Chemistry Chemistry • Is the study of matter – Composition: what matter is made of – Structure: how matter is assembled – Change: how matter can be changed Good Accuracy • The known value • Value closely agrees with accepted values Poor Precision • Human error • Limitations of the measuring instrument Precise • The student massed the pennies – She got values of 3.012, 3.016, and 3.015 – The accepted value is 3.200. – Is her work accurate or precise? Physical change • • • • • • Chemical formula stays the same H2O changes from ice to water to steam Paper can be crumpled or cut Plastic can melt Car can be dented Shirt can be ironed Chemical Change • • • • • • • Reaction to acid Reactivity to oxygen Difference in electrical potential Chemical formula changes Aluminum pot bottom shines with cleaner Candlestick tarnishes Potato clock runs on difference in potential between between copper and zinc • Milk curdles in lemon juice Matter • TWO PROPERTIES – Mass – Volume • Not Matter – Light – Vacuum Density • Concerns two properties – Mass – Volume – Density is mass divided by volume – D = m/v States of matter • SOLID – Definite shape – Volume definite States of Matter • LIQUID – Volume definite – Shape not definite States of Matter • GAS • Volume not definite • Changes shape to fit container Mixtures • Homogeneous – Solutions – The same all through – Salt water, lemonade no pulp, tea • Heterogeneous – With pieces – Lemonade with pulp, fruit salad, potato salad Significant Figures • • • • • • • • 12 1098 2001 2.001 x 103 0.0000101 1.01 x 10-5 1,000. 22.0403 2 4 5 4 3 3 4 6 Round to 4 significant figures • • • • • • 123.431 1.23431 12,434.1 550,092 90,221 Rounded 123.4 1.234 12,340.0 550,100 90,220 Round to 3 Significant Figures • • • • 0.000032421 7,212,992 2.098988 x 10-7 550,092 • 199.99 .0000324 7,210,000 2.10 x 10-7 550,000 NO is 2 5.50 x 105 200. or 2.00 x 102 Round to indicated Sig Figs • • • • 102.4005 15.995 1.6385 7.355 to five to three to four to three 102.40 16.0 1.639 7.40 Round to indicated Sig Figs • • • • 0.50045 126.5 15.395 23.0975 to four to three to four to five .5005 127 15.40 23.098 Multiplying with Sig Figs • When numbers are multiplied, the answer should contain the same number of sig figs as the multiplier with the LEAST number of sig figs. Dividing with Sig Figs • When numbers are divided, the answer should contain the same number of sig figs as the multiplier with the LEAST number of sig figs. Adding,subtracting with Sig Figs • When numbers are added or subtracted, the limiting term is the one with the SMALLEST NUMBER OF DECIMAL places.