Unit 1: Fundamental Chemistry

CHEMISTRY: the science of materials, their composition and structure, and the changes they

undergo.

Six Branches of Chemistry

Physical chemistry Analytical chemistry Inorganic chemistryOrganic chemistry BiochemistryNuclear chemistry

Foundation of Chemistry

To study the chemical system(s) and the CHANGES they undergo.

Initial state →Final StateA + B → AB

All of our known facts in chemistry are based on the study of chemical reactions

REACTION: a chemical change in which a new substance is formed.

NaCl + AgOH → AgCl + NaOH

Left side called the REACTANTS

Right side called the PRODUCTS

An important objective of science:

Relate properties of Large samples of matter (called macroscopic) to the individual atom (microscopic)

Scientific Method – used all the time

Step 1: Making Observations

Two types of Observations:

QUALITATIVE: a descriptive term. “Your shirt is red,” “The solution was bubbling and was pink”, “The water is a liquid at room temperature.”

QUANTITATIVE: a quantitative observation is called a MEASUREMENT. “The pressure was 1 atm”

Scientific Method

Step 2: Looking for patterns in the observations

Usually results in the formulation of a natural law

NATURAL LAW: a statement that expresses generally observed behavior. A natural law is often expressed as a math formula

Ideal Gas Law: pV = nRT

Scientific Method

Step 3: Formulating Theories

THEORY: also called a model. It consists of a set of assumptions put forth to explain the observations. Back in the day we called this a hypothesis.

REMEMBER: an observation is a FACT

A theory is an interpretation (can be wrong!!)

Scientific Method

Step 4: Experiment to Test Theories

Experiments may and usually do lead to modified or changed theories.

Scientific Method

↓LAW↓Theory ← Modify Theory↓ ↗Test Theory/Experiment

Observations

Units of Measurement

A MEASUREMENT consists of two parts: a NUMBER and a UNIT. Both must be present.

There are two types of units.

FUNDAMENTAL UNITS

These are units upon which all other units are based.

METER – length

GRAM – measures mass. Mass – quantity of matter that a body possesses.

WEIGHT – measure of the earth's gravitational field.

Remember: your mass is FIXED but your weight varies depending on your position from the center of the earth

FUNDAMENTAL UNITS

SECOND – measures time (based on the vibration of Cesium-133)

MOLE – measures the number of particles and is equal to 6.02 x 10 to the 23rd.

KELVIN – named after Lord Kelvin. Kelvin temperature scale is based on absolute zero.

COULOMB – a quantity of electrical charge

DERIVED UNITS

Derived units are units based on fundamental units. There are lots and lots of derived units. Two examples:

VOLUME – 1 mL = 1 cubic centimeter = 1 gram (if water)

1 Liter = 1 cubic decimeter

1 Liter – 1000 cubic centimeters

DERIVED UNITS

Density is another derived unit based on mass and volume

Density = Mass/Volume

Units for Density are grams/mL

UNCERTAINTY IN MEASUREMENT

All measurements have some degree of

uncertainty

5 different nerdy honors chemistry students massed a sample of iron:student 1 = 16.18 gstudent 2 = 16.15 gstudent 3 = 16.19 gstudent 4 = 16.16 gstudent 5 = 16.15 gWhich decimal place do you think was likely to be rounded? Most exact?? Least exact??

Significant Figures: certain digits and the first uncertain digit. (the real reason we need sig figs is to help us figure out which numbers are exact and which ones were rounded)Sig Figs are used mainly in the fields of physics and engineering.

Measuring the sides of a square:area = (side)(side)area = (16.4 cm) (22.8 cm)area = 373.92 cm2

Look at the answer the calculator gives us. It is IMPOSSIBLE (for a plain orange pumpkin to become a golden carriage) to have an answer that is MORE accurate than our measurements – thus the need for sig figs in the physical sciences.

Rules for Counting Sig Figs1. Non Zero Integers

Non zero integers always count as significant figuresie. 3.455 has 4 sig figs

2. ZerosThere are THREE (really 4) rules for Zeros:1. LEADING ZEROS - are zeros that precede all of the non-zero digits. They DO NOT count as sig figs. Note that leading zeros are always in a very small number)ie. The number 0.000456 has 3 sig figs. The leading zeros are

not significant and are only there to simply indicate the position of the decimal point.

2. CAPTIVE ZEROS (OR SANDWICHED ZEROS) – are zeros between two non-zero digits. They are ALWAYS

significant. ie. the number 1.008 has FOUR sig figs.

3. TRAILING ZEROS – these are zeros at the right end of the number. There are two rules for trailing zeros:

a. They ARE significant if the number has a decimal point.b. They are NOT significant if there is no decimal point. The number 100 has only 1 sig figThe number 1.00 x 102 has three sig figsThe number 2306.00 has six sig figs

Now you have fun and practice!!Determine the # of sig figs in:236 678.09

1.008 0.000056709

8,900 0.00509080700

Rules for Math and Sig Figs

1. Addition/SubtractionThe result has the same number of decimal places as the least precise measurement. HINT: Count

Decimal Places.Ie. 12.11

18.0 ← here is the limiting term-only 1 dec. place + 1.013 31.123

But the CORRECTED answer with one decimal place

would be 31.1

2. Multiplication/Division

The number of sig figs in the product/quotient is the same as the number of sig figs in the LEAST precise measurement. HINT: count the sig figs

ie. (4.56)(1.4) = 6.38 …but you can’t really have an answer with MORE sig figs than the number with the least…so the CORRECTED answer would be 6.4.

(3 sig figs)(2 sig figs) = 2 sig figs

Now YOU get to have fun!!! Give the answers to the correct # of sig figs1. 2.33 + 4.5 + 8.00 + 8 =

2. 9.010 ÷ 3.7 =

3. 9.0 – 3.888 =

4. (5.66)(1.00)(2.00)(0.0006) =

Precision vs. Accuracy

These concepts are often confused!!!

ACCURACY – denotes the nearness of a measurement to its accepted value.

ie. beaker mass = 19.0 grams

Your mass = 19.9 g, 24.1 g, and 13.6 g.

How was this student's accuracy?????

PRECISION

An agreement between the numerical values of a set of measurements that have been made the same way (think CONSISTENCY!!)

ie. Beaker mass = 19.0 g

Your mass = 14.1 g, 14.0 g, and 14.1 g

How was your precision?

How was your accuracy?

Dart example

Percentage Error Formula

% error = |experimental - actual| x 100

actual

PERCENTAGE ERRORA student was calculating the % of lead (Pb) in the water at Xenia High School in the drinking fountains. She came up with the following values: 16.12%, 16.14%, 16.12% and 16.13%. The average value was 16.13%. The correct value according to my scientific calculations was 16.49%.

What can be said about the accuracy?

What can be said about the precision?

Calculate the % error.

SCIENTIFIC NOTATION

Also called exponential notation

Move the decimal to the left – exponent is larger and POSITIVE!! For example the speed of light is 30,000,000,000 cm/sec. Put into scientific notation.

Move the decimal to the right – exponent is smaller and negative. For example, put 0.000496 m into scientific notation.

Fun with Scientific Notation (you junior science nerd you!)

(9.24 x 1016 )(6.12 x 1014 ) =

1.96 x 10-8 /2.47 x 10-4 =

DIMENSIONAL ANALYSIS

An exciting and fun way of working problems by using the UNITS to help us along the way.

Defined: a method of changing units.

(use the metric/English or English/metric charts)

Doing conversions using Dimensional Analysis:Convert 14 Kg to lbs:

Convert 16.9 in to cm:

Convert 8 years to seconds:

Convert 3 gallons to mL

Convert 8 mph to cm/second

Convert 4.66 in2 to cm2

Convert 98.77 yd3 to m3

Convert 4.5 m to Km

Convert 0.455 mL to cL

TEMPERATUREThree systems: Celsius, Kelvin, Fahrenheit

For Water: BP = 212ºF, 100ºC, 373K

For Water: FP = 32ºF, 0ºC, 273 K

Special Formulas

°C = (°F – 32)5/9

°F = (°C X 9/5) + 32

K = °C + 273

°C = K – 273

Normal body temperature is 98.6ºF. Convert to ºC and Kelvin.

Liquid nitrogen has a boiling point of 77K. Convert this to ºF.

DENSITYDensity is defined as the mass of a substance per unit volume.

Density = M/V

This formula can also be solved for mass and volume.

M =

V =

The mass of Al is 14.2 g and the volume is 6.9 mL. Find the density

Calculate the % error (the actual density is 2.7 g/mL)

The density of Fe is 7.86 g/mL. You have 29 grams of Fe. How many mls will it occupy?

Percentage ProblemsPercentage is a part/whole x 100

Given: 82 g of a metallic powder. It consists of 31 g of Zn, 3 g Ag, and 48 g of Sn. Find the % of each.

Flow Chart of Matter

MATTER

Pure Substance Mixtures

Heterogeneous Mixture

Homogeneous Mixture

Pure Substance

Compound Elements

Atoms

Nucleus Electrons

Protons Neutrons

QuarksQuarks

SEPARATION METHODS

There are Nine (9) ways to separate mixtures in the lab. Some of these are based on physical properties and some of these are based on chemical properties.

1. FILTRATION

Separates based on insoluble/soluble properties

FILTRATE: the soluble substance or liquid that passes through the filter paper

RESIDUE: the insoluble chunky “stuff” that remains in the filter paper.

Filtration is a great way to separate a SUSPENSION: where the particles are larger than molecular size in the liquid.

SOLUBILITY

Solubility in water is a physical property

SOLUBLE: dissolves

INSOLUBLE: remains undissolved

2. DECANTING

Decanting is used to separate a coarse suspension of liquid and dense, insoluble solids.

Decanting simply means “to pour off”

Yes...even you can do this separation technique!

3. SIMPLE DISTILLATION

Distillation is used to separate solid solute from liquid solvent

Distillation is used to make distilled water and many different alcohol products.

Distillation is based on a phase difference (the solid remains in the original flask and the liquid boils, evaporates, then condenses and drips into a new container in a purified form)

4. Fractional Distillation

Used to separate miscible liquids

MISCIBLE LIQUIDS – liquids that are soluble in each other (alcohol in water)

IMMISCIBLE LIQUIDS- liquids that are NOT soluble in each other (oil in water)

Fractional distillation separates based on the boiling points of the liquids

4. Fractional DistillationExample: you have a mixture of two liquids – alcohol and water. Alcohol has a boiling point of 80°C and water has a boiling point of 100°C.

The liquids boil off one by one at their boiling point temperatures.

Fractional distillation is used in the petroleum industry (petroleum products)

Many products come from crude oil: drugs (legal ones of course), cosmetics, kerosene, oil, gas, plastics, etc.

Petroleum products based on fossil fuels

5. FRACTIONAL CRYSTALLIZATION

Separates based on soluble solids whose solubility differs in hot and cold water

Example: solid X is very soluble at all temperatures

Solid Y is soluble only in hot water

Dissolve both in hot water; cool the water; solid Y comes out of solution because Y is insoluble in cold water.

6. EXTRACTION

Uses a device called a SEPARATORY FUNNEL

Extraction is used to separate immiscible liquids (like oil and water)

IMMISICIBLE LIQUIDS – not soluble in each other

MISCIBLE LIQUIDS – liquids that are soluble in each other

7. Chromatography

Separates substances by differences in dissolving rates

Chromatography is used to separate COLORS and PROTEINS

Chromatography is used to do various analysis' of DNA (paternity tests, etc)

8. ELECTROPHORESIS

Separates based on the charge of the particles

Remember: like charges repel; unlike charges attract

Must have an electrical field with positive and negative electrodes in order for electrophoresis to work.

9. CENTRIFUGATION

Uses a device called a centrifuge to settle and separate sediments

Separates based on the different densities of the particles in the mixture.

How would YOU separate the following mixtures?a. flour and water

b. sugar solution and sand

c. 70% ethanol/water solution

d. oil, water and sand

e. Mercury and water (Hg is a really heavy metal and is a liquid)

f. chlorophyll pigments

g. sugar and Kool-Aid