chemistry 171 lec (1)

8/4/2019 Chemistry 171 Lec (1)

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Chemistry is branch of physical science that deals with the study of matter, its phases, properties,

composition, structures, and the energy that is released or absorbed during chemical changes.

Branches of Chemistry:

1. General Chemistry - the study of all branches of chemistry with emphasis on primaryconcepts and simple laws.

2. Inorganic Chemistry the study of non-carbon containing substances.3. Organic Chemistry the study of carbon and its compounds.4. Biochemistry the study of chemical changes affecting all living organisms.5. Thermochemistry the study of energy changes in matter.6. Electrochemistry the study of conversion of chemical energy to electrical energy.7. Industrial chemistry deals with the conversion of raw materials into finished products.8. Nuclear chemistry the study of radioactivity and the peaceful uses of nuclear energy.9. Physical chemistry the study of the development of the theoretical aspects of chemistry.10.Applied chemistry deals with the application of chemical principle in everyday life.11.Environmental chemistry - the study of environmental problems and their corresponding

solutions.

12.Pharmaceutical chemistry deals with the manufacture of drugs and medicines.13.Geochemistry- the study of chemical composition of earth.14.Micro logical chemistry- the study of earth compounds called minerals.15.Analytical chemistry deals with the identification of the kinds and amounts of elements present

in a given sample. It can be a qualitative or quantitative analysis.

Objectives:

1. To study the characteristics and properties of the different materials in order to distinguishthem from one another.

2. To find the conditions necessary for promoting or preventing changes in matter.3. To devise ways and means of separating one substance from another.4. To devise ways and means of transforming raw materials into synthetic products necessary for

the enjoyment and enrichment of human life.

5. To determine the amount of matter and energy involved in a given changes.

Catalysts are substances that may promote or prevent changes in matter without undergoing any

permanent chemical change.


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Chemical equation is short hand notation for a chemical transformation.

Types of Chemical Equations:

1. Synthesis (S) A + B AB2. Analysis (A) AB A + B3. Displacement (D) AB + C A + CB

(substitution)

4. Metathesis (M) or (DD) AB + CD AD + CB(double decomposition)

Steps in balancing simple chemical equation by inspection:

1. Find the most complex formula (MCF)2. Balance as to the coefficients. (coefficient is a number before a chemical expression to denote

the number of molecules; subscript is the small number written below the symbol of the

element to denote the number of atoms)

Example: 9C6H12O6 (glucose)

Total number of atoms per element = coefficient x subscript

C= 9x6 = 54, H= 9x12 = 108, O = 9x6 = 54

(Total number of atoms= 54+108+54 = 216)

Illustrations:

1. 4Al + 3O3 2 Al2 O3, 4Fe O + O3 2 Fe2 O3 (synthesis)2. 2H2O 2H2 + O2 , C12 H22 O11 12C + 11H2 (analysis)3. 3Zn + H3BO3 3H2 - Zn3 (BO3)2 (displacement)4. 3Ca (OH)2 + 2H3 PO4 Ca3(PO4)2 + 6H2O (metathesis)


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MEASUREMENTS

Measurements are always uncertain because measuring instruments are never flawless and because

measuring always involves some estimation. It is important that measurements in science have both

high precision and high accuracy.

SI BASE UNITS

Physical Quantity Unit name and Symbol

Mass kilogram, kg

Length meter, m

Time second, s

Count quantity mole, mol

Temperature Kelvin, K

Electric current ampere, A

Luminous intensity candela, cd

DERIVED UNITS COMMONLY USED IN CHEMISTRY

Physical Quantity Unit name and Symbol

Area square meter, m2

Volume cubic meter, m3

Force newton, N

Pressure pascal, Pa

Energy joule, J

Power watt, W

Voltage volt, V

Frequency hertz, Hz

Electric charge coulomb, C


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COMMON METRIC PREFIXES USED IN CHEMISTRY

Prefix Abbreviation Meaning

Mega M 106

Kilo k 103

Deci d 10-1

Centi c 10-2

Milli m 10-3

Micro u 10-6

Nano n 10-9

Pico p 10-12

The certain digits and the estimated digit of a measurement are together called the significant digits of

the measurement. For example, there are three significant digits in 31.7 milliliters: two certain digits

(the 3 and 1) plus the estimated digit (the 7).

When a number is written in scientific notation, is separated in two parts. The first part is a number

between 1 and 10. The second part is a power of ten. This is used to write very large or very small

numbers. For example, the number 0.00225 written in scientific notation is 2.25 x 10-3.

PERCENTS AND PERCENT ERROR

Percent error = (measured value accepted value)/accepted value x 100 percent.

In chemistry, density is one of the important properties of matter. Density is equal to the mass of a

substance per unit volume.

Density = mass /volume ( in g/cm3 or in kg/m3)

Density of solid is greater than that of liquid, and density of liquid is greater than that of gas.

dsolid > dliquid > dgas


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Density of some common substances

Substance Density (g/cm3)

Air 0.0013 (at 0 *C and 1 atm pressure)

Ice 0.917

Water 1.00

Aluminium 2.70

Iron 7.86

Gold 19.3

Relative density or specific gravityis a dimensionless quantity that compares the density of a substance

to that of water at standard conditions (@ 15.56 deg. C and 1 atm. Pressure, density of water = 1g/mL

or 1000 kg /m3)

Relative density = dsubstance / dwater @ std conditions (dimensionless)

To solve for the density of any substance when its relative density or specific gravityis given, we simply

multiply the relative density by 1000 kg/m3.

Many chemistry problems involve converting measurements from one unit to another. Another name

for the unit of a measurement is dimension. The technique of converting between units is called

dimensional analysis.

UNIT EQUALITIES

Metric to Metric

1000 m = 1 km 1 m = 100 cm 1 m = 1000 mm 1 m = 1 x 106

um

1 m = 1 x 109 nm 1 m = 1 x 1012 pm

1 cm = 0.01 m 1 mm = 0.001 m 1 um = 1 x 10-6

m 1 nm = 1 x 10-9

m

1 pm = 1 x 10-12 m

1 L = 1000 cm3

1 mL = 1 cm3

English to Metric

1 in = 2.54 cm 1 gal = 3.785 L 1 cal = 4.184 J 1 atm = 101,325 Pa


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Miscellaneous

1 ft = 12 in 1 mi = 5280 ft 1 min = 60 s 1 hr = 60 min

1 atm = 760 mm Hg

A unit equality is the starting point for solving the problem. It is an equation that shows how different

units are related.

The next step in solving the problem is to write the conversion factors from the unit equality. A

conversion factor is an equation that is always equal to 1.

The four steps that can be used to solve problems in chemistry are analyze, plan, solve, and evaluate.

ENERGY AND MATTER

Energy is the capacity to do work or to produce heat.

Energy comes in many forms, but they can be conveniently classified into just three categories: radiant

energy, kinetic energy, andpotentialenergy.

Radiant energy: sunlight

Kinetic energy: energy carried by objects in motion; thermal energy which is caused by the random

internal motion of particles of matter.

Potential energy: energy possessed by objects because of their position or the arrangement of their

particles.

Common unit of energy is the calorie (cal). One calorie is the amount of heat needed to raise the

temperature of 1 gram of water by 1 Celsius degree.

Unit equality: 1 cal = 4.184 J , J= Joule

Law of conservation of energy: in any process, energy is neither created nor destroyed. Process means

any situation in which energy is transferred from one object to another or transformed from one kind of

energy into another kind.

Temperature:

Temperature is a measure of how hot or cold something is.

The Celsius and Kelvin temperature Scales.

To convert Celsius temperatures to the Kelvin scale, add 273:

K = *C + 273


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The zero point of the Kelvin scale called the absolute zero, corresponds to -273 *C.

Absolute zero is the point at which the motion of particles of matter, their kinetic energy, ceases.

STATES OF MATTER

Matter is anything that has mass and volume. All kinds of matter have certain characteristics, or

properties. These properties are either physical properties or chemical properties.

STATE EXAMPLE CHARACTERISTICS

Solid Gold High density. Density little affected by pressure.

Holds its own shape in a container.

Liquid Water High density. Density little affected by pressure.

Adopts the shape of its container.

Gas Nitrogen Low density. Density depends on pressure.

Expands to fill its container.

Plasma Interior of the sun Low density. Density depends on pressure.

Exists only at high temperatures

Changes in Matter:

Physical Changes changes which do not alter the identity of a substance. Examples are changes in form

and state of the substance.

Chemical Changes

in contrast to physical changes, chemical changes or chemical reactions do alter theidentity of a substance. A piece of iron exposed to moist air is chemically changed as it rusts.


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ELEMENTS AND COMPOUNDS

An elementis a substance that cannot be separated into simpler substances by a chemical change.

When two or more elements combine in a chemical reaction, they form a compound.

Elements and compounds are examples of pure substances.

Mixtures

A mixture is a blend of two or more pure substances.

Mixtures are either heterogeneous or homogeneous.

Heterogeneous mixtures can often be separated byfiltration.

Homogeneous mixtures can be separated by distillation, crystallization, and chromatography.

chemistry 171 lec (1)

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