CHEM 1030 Dr. Streit- Week 1 Notes
CHEM 1030 Dr. Streit- Week 1 Notes CHEM 1030 - 003
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This 5 page Class Notes was uploaded by Rachel Ferrell on Friday January 22, 2016. The Class Notes belongs to CHEM 1030 - 003 at Auburn University taught by John D Gorden in Fall 2015. Since its upload, it has received 181 views. For similar materials see Fundamentals Chemistry I in Chemistry at Auburn University.
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Date Created: 01/22/16
Rachel Ferrell CHEM 1030-‐003 1/19/16 Chapter 1: The Study of Chemistry • Chemistry-‐ the study of matter and changes matter undergoes • Matter-‐ anything that has mass and occupies space • Molecules-‐ tiny pieces of a substance; made up of atoms The Scientific Method: • Scientific method-‐ a set of guidelines in place for scientists to ensure their findings can be widespread and valid o 1) Gather data via observations and experiments o 2) Find patterns or trends in collected data o 3) Summarize findings with a law-‐ a concise statement that makes relations between phenomena o 4) Formulate hypothesis-‐ means tentative explanation o 5) Hypothesis evolves into theory-‐ unifying principle that explains a large set of experimental observations; can also predict phenomena that have not happened yet Classification of Matter: • classify matter as either a substance or a mixture o Substance-‐ a form of matter that has a definite composition and distinct properties § ex. Salt (NaCl), water (H2O), carbon dioxide (CO2), oxygen (O2) § these elements are combined chemically; must exist together to keep same properties § differ in substances as well as color, taste, smell, etc. o Mixture-‐ a physical combination of 2 or more substances § Homogeneous mixture-‐ uniform throughout; solutions • Ex. Sea water, apple juice § Heterogeneous mixture-‐ not uniform throughout • ex. Trail mix, chicken noodle soup • can be separated by physical processes that do not change identity of substance • States of matter: o Solids-‐ particles close together in orderly fashion; does not conform to shape of container o Liquids-‐ particles close together but not rigid in position; does conform to shape of container o Gases-‐ particles far apart; conforms to shape and volume of container o All substances can exist as any of these states of matter o Changing states does not change identity of the substance Properties of Matter: • Quantitative properties-‐ measured/expressed by numbers • Qualitative properties-‐ no measurement; based on observation • Physical properties: o Can be observed or measured without changing the identity of the substance o Ex. Color, melting point, boiling point, o Physical change-‐ state of matter changes, but the identity does not change; like changing between a solid, liquid or a gas • Chemical properties o A property shown when substance reacts with another substance; it is no longer is the same substance o Ex. Flammability, corrosiveness o Chemical change-‐ change substance’s composition, original substance is gone o ex. Digestion, combustion, oxidation • Extensive properties o a property of measured value that depends on the amount of matter o ex. Mass, volume • Intensive Properties o a property that does not depend on the amount of matter o ex. Temperature, density Scientific Measurement: • any measured quantity must have a unit • SI Base Units o Revised metric system (International system of units) o Designed to be universal for scientists o 7 SI Base Units: o Base quantity o Name of unit o Symbol o Length o Meter o m o Mass o Kilogram o kg o Time o Second o s o Electric current o Ampere o A o Temperature o Kelvin o K o Amount of substance o Mole o mol o Luminous intensity o Candela o cd o the magnitude of a unit is tailored to fit a particular application using prefixes to the base units o Tera-‐ o T o 1X10^12 o Giga-‐ o 1X10^9 G o Mega-‐ o M o 1X10^6 o Kilo-‐ o k o 1X10^3 o Deci_ o d o 1X10^-‐1 o Centi-‐ o c o 1X10^-‐2 o Milli-‐ o m o 1X10^-‐3 o Micro-‐ o μ o 1X10^-‐6 o Nano-‐ o n o 1X10^-‐9 o Pico-‐ o p o 1X10^-‐12 • Mass o Measure of amount of matter in an object or sample o Weight-‐depends on gravity o Mass-‐ does not change o The Atomic Mass Unit (amu)= used to express the mass of atoms and other things of similar size § 1 amu= 1.6605378X10^-‐24 g § essentially-‐ 1 amu is very small • Temperature o Celsius Scale § Freezing point= 0°C § Boiling point= 100°C o Kelvin Scale § The “absolute scale” § Lowest possible temp= 0K (absolute zero) § Kelvin is considered an SI unit o To convert between C and K: § K= °C +273.15 § C= K-‐273.15 o Fahrenheit scale § Freezing point= 32°F § Boiling point= 212°F § Good for body temperature because 1°F=9/5 °C; therefore making it more of an exact measurement § Temp in °F= (9/5 X temp in °C) +32°F Rachel Ferrell CHEM 1030 1/21/16 Chapter 1 cont. Derived Units: Volume and Density • Volume/density-‐ require units that are not found in SI units • Must use SI Units in combination with each other • SI Unit for Volume= m or L (liters is a more practical measurement) o 1 dm = 1L o 1 cm = 1 mL o the units for volume are cubed because length X width X height of a cube • Density o Density is the ratio of mass to volume ▯ o d = Also note that v▯ and m=d x v ???? o d= density o m=mass o v=volume 3 o SI Derived unit= kg/m o Common units are based on states of matter: § g/cm = solids § g/mL = liquids § g/L = gases Uncertainty of Measurement: • 1) Exact Measurement: o =those that have defined values § 1 kg = 1000g § 1 dozen = 12 objects o =those determined by counting § 28 students in the class • 2) Inexact Measurement: o measured by anything other than counting; accounts for human and machine/tool error § ex. Length, mass, volume, time, speed, etc. § anything you have to use a tool to measure o an inexact number must be reported to show uncertainty Significant Figures (aka Sig Figs): • =meaningful digits in a set of reported numbers o the last digit= uncertain digit • ***Sig fig Rules*** o 1) Any nonzero digit is significant § 112.1= 4 sig figs o 2) Zeros between nonzero digits are significant § 305 = 3 sig figs § 50.08 = 4 sig figs o 3) Zeros to the left of the first nonzero digit are not significant § 0.0023 = 2 sig figs § 0.00000001 = 1 sig fig o 4) Zeros to the right of the last nonzero digit are significant if decimal is present § 1.200 = 4 sig figs o 5) Zeros to the right of the last nonzero digit in a number with no decimal may or may not be significant § 100 = 1, 2, or 3 sig figs § to avoid this ambiguity, write these types of numbers in scientific notation, so that no extra zeros are present • Sig Figs: Adding and Subtracting: o Answer can’t have more digits to the right of decimal point than any of the original numbers o 102.50 + 0.231 102.731 Round to 102.73* o • Sig Figs: Multiplication and Division o Determined by original number with the lowest number of sig figs o 1.4 X 8.011 = 11.2154→round to 11 (2 sig figs) o 11.57 / 305.88 = 0.0378252→ round to 0.03783 (4 sig figs) • Exact numbers can be considered to have infinite number of sig figs o If there are exact numbers in a problem, do not use them do determine number of sig figs • Sig figs only apply to inexact numbers (numbers that are not counted) Rounding Rules: • Round only after all steps of the problem have been completed • <5→round down • ≥ 5 → round up Accuracy and Precision: • 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 o ex. 1) you hit 3 darts on the bull’s-‐eye→ good accuracy and precision o 2) You hit 3 darts to the right of the bull’s-‐eye→bad accuracy, good precision o 3) You hit 3 darts in 3 different places not on the bull’s-‐eye→ bad accuracy, bad precision Using Units and Solving Problems: • conversion factor= a fraction in which same quantity is expressed one way in the numerator and another in the denominator o ex. ▯ ▯▯ OR ▯.▯▯ ▯▯ ▯ ▯▯ • dimensional analysis= use of conversion factors in a problem; factor label method
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