Chapter 1 Matter and Measurement

What is Chemistry? The study of all substances and the changes that they can undergo The CENTRAL SCIENCE

Why Study Chemistry? Useful for other sciences Required course Required course Fun and Challenging Remember: –Process of Discovery –Understand Concepts, NOT Single Facts

Scientific Method Observation Question Hypothesis Experiment Conclusion

Scientific Method Natural Law Explains how nature behaves Theory Explains why nature behaves in a certain way Conclusion PredictionExperiment

Liquids

Liquids DefiniteMolecules Not affected by

Solids

Solids Don’t DefiniteMolecules

Gases LowDensity Expands to Indefinite Molecules move

The Metric System The International System of Units Standards of measurement Base units (7) – Fig 1-14 p MASS: 2.LENGTH: 3.TIME: 4.COUNT, QUANTITY: 5.TEMPERATURE: 6.ELECTRIC CURRENT: 7.LUMINOUS INTENSITY:

The Metric System Derived Units:  AREA:  VOLUME:  ENERGY:  FORCE:  PRESSURE:  POWER:  VOLTAGE:  FREQUENCY:  ELECTRIC CHARGE:

The Metric System Metric Prefixes – make base unit larger or smaller Based on 10 Math method vs. “Stairs”

Convert a volume of 12 microliters into centiliters Express a distance of 15 meters in kilometers Convert 83 cm into meters Which is the longer amount of time, 1351 ps or 1.2 ns? Convert 16 dL into L Conversion Practice

Types of Measurements Mass – amount of –Expressed in –Does not Weight – –Expressed in –Changes with

Types of Measurements Volume – the amount of – –Many instruments to measure Temperature – – –Degrees –Degress

Density Common ratio used in chemistry Physical property of a substance SI units: Solid – Liquid – Gas – Can change due to temperature and/or pressure changes

Density 1.Find the density of a piece of metal with a volume of 2.7 cm 3 and a mass of 10.8 g. 2. Determine the mass of an object with a density of 0.24 g/cm 3 and a volume of 2 cm 3.

Uncertainty in Measurement Why are digits in measurements uncertain? 1.Instruments never completely free of flaws 2.Always involves estimation  Choose the right instrument for the job  May be estimated for you (electronic scales)  Scale is marked but you estimate the in- between

Uncertainty in Measurement Precision:Accuracy:

Significant Digits All digits known with certainty plus one final digit which is uncertain (or estimated) All non-zeros are A zero is significant when : –It is A zero is not significant when: –It is

Significant Digits - PRACTICE How many significant digits? ,000, ,000,000.1

Significant Digits - Calculations Addition and Subtraction – = becomes = = = = = =

Significant Digits - Calculations Multiplication and Division –The answer has as many sig figs as the number with the fewest sig figs 14.8 x 3.1 = becomes x 3.0 = 52/1.5 = x 1 = 2400 x = 15000/ =

Scientific Notation Convenient way of writing very large or very small numbers and showing only significant figures Number between 1 & 10 with a power of ten 5120 becomes 5.12 x 10 3 Move decimal point in original number to make number 1-10 Move left = +; move right = -

Scientific Notation Practice 123,000 = = = = 1,000,000 =

Scientific Notation Adding and subtracting Multiply and divide 3.38 x 10 3

Conversion Factors Enable movement between metric system and “English” system See back cover of book and Appendix III Common conversions you should memorize –1 inch = 2.54 cm –1 mile = km –1 kg = 2.20 pounds –1 mL = 1 cm 3 –0 K = C – 0 F = 1.8( 0 C) + 32

Dimensional Analysis (Problem Solving) Remember: ALWAYS use UNITS OF MEASUREMENT in your work!!! A technique of converting between units –Same system (metrics) –Different systems (inches to meters) –Chemical equations….later chapters…

Dimensional Analysis (Problem Solving) Conversion Factors: ratio derived from the equality between 2 different units CF can be written either way

Dimensional Analysis (Problem Solving) The “t” method Example: How many liters are in gallons? Conversion Factor

How many seconds are in 4.15 hours? Dimensional Analysis (Problem Solving) If a student needs 1.5 mL of water, how many cups does he need?