chemistry notes : chapter 1

7/27/2019 chemistry notes : chapter 1

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Matter,Measurement andCalculations

Chemistry and the Scientific MethodMatter, Properties and Changes

Classification of MatterMeasurement and UnitsAccuracy and Precision

Significant FiguresExamples of Units in Calculations

ajor divisions

Biochemistry Study of biological chemicals

Organic Carbon based compounds

Inorganic All other elements

Analytical Methods of analysis

Physical Theory and concepts

Scientific methodAll scientific studies follow the same approach toexamining a problem.

The scientific method requires that we -

Apply logical, organized reasoningto any observations made.

Form a hypothesis.

Reject or confirm that hypothesis

through experiments.

Scientific method

Observation

Descriptions and measurements.

Pattern Recognition

Cause and effect of relationships & trends.

Develop

Make hypothesis and then test it.

Experimentation

Create and use tests to prove or disprove yourhypothesis leading to atheory.

Yes

No


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Chemical properties

Wood+O2D

CO2+H2O+ heat

Ma ter

Pure Substance Mix ure

Element(Iron)

Compound(Hemoglobin)

Homogeneous(Plasma)

Heterogeneou(Blood)


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Formula BP (oC)

Density(g/L)

Other

Hydrogen H2 -253 0.90 Flammable

Oxygen O2 -218 1.14Supports

combustion

Water H2O 100 1000 Not flammable

Question Does eating junkweight gain?

food cause

ExperimentMeasure weight,

week and see w

pig out for a

at happens.

DataInitial weight

119 lb

Final weight

125 lb

Gain = final weight - initial weig

Gain = 125 lb - 119 lb = 6 lbs


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Measurement in chemistry

1 barrel = 42 gallons

1 gallon = 4 quarts

1 quart = 4 cups

1cup = 16 tablespoons

1 tablespoon = 3 teaspoons

How many teaspoons of oil are in a barrel?

1bbl# 42bblgal# 4

galqt# 4

qtcup# 16

cuptbl# 3

tbltsp

= 32 256 tsp

Metric unitsOne base forYou then use

each type of mrefixes to cha

easurement.ge size.

Some com on base units

Type Name Symbol

Mass gram g

Length meter m

Volume liter l

Time second s

Energy joule j

Prefix Symbol Factor

giga G 10 9 1 000 000 000

mega M 10 6 1 000 000

kilo k 10 3 1 000

---- 10 0 1

deci d 10 -1 0.1

centi c 10 -2 0.01

milli m 10 -3 0.001

micro 10 -6 0.000 001

nano n 10 -9 0.000 000 001

pico p 10 -12 0.000 000 000 001

We change the prefix to alter the size of the unit. How may milligrams (mg) are in a kilogram (kg)?

1 kg = 1000 g

1 g = 1000 mg

answer= 1kg : 1000 kgg

: 1000 gmg

answer= 1000 000mg


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SI - System InternationalSystem International

Systematic subset of the metric system.

Only uses certain metric units.

Mass kilograms

Length meters

Time seconds

Temperature kelvin

Amount mole

Other SI units are derived from base SI units.

Factor label method

Regardless of the type of calculation,keeping track of the units makes thingcome out right.

Must use conversion factors - relationshipbetween two units

Canceling out units is a way of checkingthat your formula is set up right!

English FactorFactor

1 gallon = 4 quarts 4 qt/gal

1 mile = 5280 feet 5280 ft/mile

1 ton = 2000 pounds 2000 lb/ton

Common English to Metric conversions

FactorFactor

1 liter = 1.057 quarts 1.057 qt/l

1 kilogram = 2.2 pounds 2.2 lb/kg

1 meter = 1.094 yards 1.094 yd/m1 inch = 2.54 cm 2.54 cm/inch

A nerve impulse in the body can travel as fast as400 feet/second.

What is its speed in meters/min ?

Conversions Needed

1 meter = 3.3 feet

1 minute = 60 seconds

m 400 ft 1 m 60 sec

min 1 sec 3.3 ft 1 min

m 400 ft 1 m 60 sec

min 1 sec 3.3 ft 1 min?? = x x

?? = x x

m

min....Fast7273

All measurements contain some uncertainty.

We make errors

Tools have limits

Uncertainty is measured using

Accuracy How close to the true value

Precision How close to each other


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Accuracy

How close ourvalues agree withthe true value.

Here, the averagewould be close tothe true answerbut the numbersdo not agree.

Large randomerror.

Precisio

How close ourvalues agree witheach other.

Here, they are allclose to eachother but notclose to the truevalue.

Large systematicerror.

Accuracy and precision

Our goal!

Good precisionAND goodaccuracy.

These are values

we can trust.

Predict the effect on accuracy and precision.

Instrument not zeroed properly

Reagents made at wrong concentration

Temperature in room varies wildly

Lab partner is not properly trained


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0 1 2 3 4 5

Method used to express accuracy & precision.

You cant report numbers better than the methodused to measure them.

67.2 units = three significant figures

CertainDigits

UncertainDigit

These numbersall have three

significant figures!

Leading zeros are notare not significant.

0.421 - three significant figuresLeading zeroLeading zero

Captive zeros areare significant.4012 - four significant figures

Trailing zeros areare significant.114.20 - five significant figures

Captive zeroCaptive zero

Trailing zeroTrailing zero

0.00321321 = 3.213.21 x 10-


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The Celsius scale isbased on themelting point (0 oC)and boiling point(100 oC) of water.

Example. oF to oC

If it is 20 oF outside, what is it in oC ?

oC = (oF - 32)5

9

oC = (20 oF - 32)5

9

oC = -6.7 (two significantfigure in 20 oF)


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HydrometerHydrometer

Float height willbe based onSpecific Gravity.

chemistry notes : chapter 1

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