chemistry- jib topic 1 matter and measurement

Chemistry – science that deals with matter and the changes that matter undergoes

Macroscopic – all around us

Microscopic – air, molecules, etc

Scientific Problem Solving3 Step Process

1. state problem and make observations (qualitative vs. quantitative)

2. formulate a possible solution3. perform experiments to test hypothesis

Theory vs. LawTheory – gives a universally accepted

explanation of the problem

Law – state what general behavior is observed that occurs normally

States of MatterAll matter has 2 characteristics

Has mass and occupies space

3 types: solid, liquid, gas

Solids – definite shape and volume; packed tightly together; vibrate gently around fixed positions

Liquids – no shape of own; fill container; definite volume; particles are free to move

Gases – no shape or definite volume; particles spread apart; filling all space in container

Physical and Chemical Properties and Changes

Physical Property: color, odor, density, hardness, solubility, melting point, boiling point

Physical Change: chemical composition always remains the same. Ex. Phase changes (2 less known ones are sublimation (solid to gas) and deposition (gas to solid)

Chemical Property: reacts with acid, reacts with base, oxidation and reduction

Chemical Change: won’t go back to original substance. Ex. combustion

E, C, MElement – pure substance that cannot be broken

down any further…..single substance from periodic table

Compound – pure substance that cannot be broken down by physical means; formed when elements bond together….have fixed composition

Mixture – varying composition and is made up of a number of pure substances.Homogeneous – uniform compositionHeterogeneous – varying composition

MeasurementScientific Notation

The number of places the decimal point has moved determines the power of 10

Decimal moves left = positive powerDecimal moves right = negative power

42000 = 4.2 x 104

0.00012 = 1.2 x 10-4

SI Units and prefixes

Base Quantity Unit Symbol

Mass Kilogram kg

Length Meter m

Time Second s

Amt. of Substance

Mole mol

Temperature Kelvin K

Prefix Symbol Meaning

Giga G 109

Mega M 106

kilo k 103

deci d 10-1

centi c 10-2

milli m 10-3

micro μ 10-6

nano n 10-9

pico p 10-12

3 scales for temperatureCelsiusKelvinFahrenheit

Celsius to Kelvin (°C + 273)Kelvin to celsius (K – 273)Celsius to fahrenheit (°C * 9/5) + 32Fahrenheit to celsius (°F – 32) * 5/9

Derived UnitsAll other units can be derived from base

quantitiesExamples:

1. Volume: unit is length3

Common units are L or mL (how much is a cm3?)

1.00 L = 1000 mL = 1000 cm3 = 1.00 dm3

2. Density = mass/volume

UncertaintyWhen reading the scale on a piece of lab

equipment, there is always a degree of uncertainty

Estimate must be made to record the final digitThis “uncertain” digit is recorded by using the

+/- scale

Rounding – don’t round until the end of a calculation

Significant FiguresRemember the Atlantic and Pacific rule

In Calculations Multiplying and dividing: limit answer to least

number of sig figs used Adding and subtracting: limit answer to same

number of decimal places that appear in the original data with fewest number of decimal places

Accuracy vs. Precision

Accuracy – relates to how close the measured value is to the actual value of the quantity

Precision – how close 2 or more measurements of the same quantity are to one another

Percent ErrorData that is derived from experiments will

often differ from the accepted, published, actual value

Common way of expressing accuracy is: | Actual – Calculated | x 100

Actual