This Chemistry Project contain information on many topics related to chemistry
Working with the Properties & Changes of Matter
Chemical- any substance that has defined composition
Everything you see is made up of chemicals
Even things you cannot see are made up of chemicals
Some exist naturally
Some are manufactured
Chemical Reaction- the process by which one or more substances change to produce one or more different substances
Physical States of Matter
Type and arrangement of particles in a sample of matter determine the properties of the matter
Most matter is one of the three states of matter
A. Properties of the Physical State
Solids- fixed volume and shape
Rigid structure
Liquids- fixed volume and variable shape
Takes shape of container
Gases- neither fixed volume or shape
Particles move independently
Will fill any container they occupy
Changes of Matter
Many changes of matter happen. Changes occur in two different ways:
Physical Changes
Chemical Changes
A. Physical Change
Changes in which the identity of a substance doesn’t change
-Changes state
-Dissolving
-Crushing
B. Chemical Changes
Identifies of substances change and new substances form.
Mercury (II) oxide mercury + oxygen
Reactants Products
-Substance or molecule that -Substance that forms in a chemical
participates in a chemical reaction reaction
Atoms are not destroyed or created, so mass does not change during a chemical reaction.
C. Evidence of Chemical Change
Generally, evidence that a chemical change may be happening falls into one of four categories; you may observe more than one.
Evolution of a gas- the production of a gas is often observed by bubbling or by a change in color
Formation of a Precipitate- when two clear solutions are mixed and become cloudy, a solid precipitate has formed
Release or Absorption of Energy- change in temperature of the giving off of light energy are signs of energy transfer
Color Change in the Reaction System- look for a different color when two chemicals react
Section 2 of Chemistry Notes Info.
I. Density
Matter has Mass & Volume
Matter- Anything that has mass and takes up space
The space an object occupies is its volume
Volume—a measure of the size of a body or region in three-dimensional space
The method used to determine volume depends on the nature of the matter being examined
Quantity of Matter is Mass
Mass- a measure of the amount of matter in an object. It is not affected by the gravitational force
Balances measure mass usually in grams
It is the same no matter where it is in the universe
Mass is NOT Weight
Weight- the force produced by gravity action on mass
Its value can change with the location of the object in the universe
Measured in Newtons
II. Units of Measurement
Mass & volume are properties that can be described in terms of numbers
Numbers alone aren’t enough because their meaning might be unclear
Units of measurement are needed with the numbers
Quantity- something that has magnitude, size, or amount
Unit- a quantity adopted as a standard of measurement
System Internationale d’Units
Seven base units
Base units can be modified by attaching prefixes
Derived Units
Many quantities you can measure need units other than the seven basic SI Units
These units are derived by multiplying or dividing the base units
Properties of Matter
Properties of substances may be classified as physical or chemical
Physical Properties
Characteristic of a substance that doesn’t involve a chemical change, such as density, color, or hardness
Chemical Properties
A property of matter that describes a substance’s ability to participate in chemical reactions
Examples: reactivity with oxygen, sensitivity to light, exposure to heat
Density
Density- the ratio of mass to volume of a substance. Often expressed in grams/cm3 for solids and liquids and g/L for gases
Density= mass/volume or D=m/v
Section 3 of Chemistry Notes Info.
Classifying Matter
-From the last section:
-Matter-anything that has mass and takes up space
-All matter is composed of Atoms
-Atom- the smallest unit of an element that maintains the properties of that element
Because matter exists in so many different forms, having a way to classify it is important for study.
It helps you to predict what characteristics a sample will have based on what you know about others like it.
Pure Substances- a sample of matter, either a single element or a single compound that has definite chemical and physical properties
Element- a substance that cannot be separated or broken down into simpler substances by chemical means; all atoms of an element have the same atomic number
There are two types of pure substances:
Elements
Compounds
Elements- are pure substances that contain only one kind of atom
Has its own unique set of physical and chemical properties
Has its own chemical symbol
Molecule- the smallest of a unit of substance that keeps all of the physical and chemical properties that of the substance; it can consist of one atom or two or more atoms bonded together
Diatomic elements- two of the same atom bonded together chemically
Pure Substances
-Some elements have more than one form
-Allotrope- one of a number of different molecular forms of an element
-Compounds are Pure Substances
Compound- a substance made up of atoms of two or more different elements joined by chemical bonds
Atoms and Moles
Section 1 Substances are Made of Atoms
I. Atomic Theory
-As early as 400 B.C., an atomic theory existed that stated that atoms are the building blocks of all matter
-Democritus was the first scientist who believed in atoms (Greek)
-It wasn't until the 1800s that atomic theory was revised based on scientific observations
A. Law of Definite Proportion
-Two samples of a given compound are made of the same elements in exactly the same proportions by mass regardless of the sizes or sources of the samples.
-Every molecule of the same type is made of the same number and types of atoms
-Example: Table Salt (Sodium Chloride)
-consists of two elements in the following proportions by mass:
-60.66% Chlorine
-39.34% Sodium
-Every sample of table salt has these same proportions
B. Law of Conservation of Mass
-The mass of the reactants in a reaction equals the mass of the products
-Mass cannot be created or destroyed in ordinary chemical and physical changes
C. Law of Multiple Proportions
-If tow or more different compounds are composed of the same two elements, the ratio of the masses of the second element (which combines with a given mass at the first element) is always a ratio of small whole numbers.
II. Dalton's Atomic Theory
- Dalton revised the early Greek idea atomic theory in the 1800s into a scientific theory that could be tested by experiments
-Has five important principals
-Believed that elements are composed of only one kind of matter and compounds are made of two or more kinds
-Part of his theory that was incorrect is the fact that like atoms can combine with like atoms (such as O2)
-Did not include the fact that atoms are made up of even smaller particles
Dalton's Theory Contains Five Principles
1. All matter is composed of extremely small particles called atoms, which cannot be subdivide, created, or destroyed
2. Atoms of a given element are identical in their physical and chemical properties
3. Atoms of different elements differ in their physical and chemical properties
4. Atoms of different elements combine in simple, whole-number ratios to form compounds
5. In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed
Section 2: Structure of Atoms
I. Subatomic Particles
A. Electrons- negative charge
B. Nucleus- an atom's central region, which is made up of protons and neutrons
1. Protons- positive charge. Number of protons is atomic number.
2. Neutrons- no charge.
II. Atomic Number and Atomic Mass
Elements differ from each other in the number of protons their atoms contain
-Atomic Number- the number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element
-Atomic numbers are always whole numbers
-Atomic number also reveals the number of electrons in an atom of an element because for an atom to be neutral, electrons must equal protons
Mass Number is the Number of Particles in the Nucleus
-Mass number- the sum of the numbers of protons and neutrons of the nucleus of an atom
Example:
mass number- atomic number= number of neutrons
In this example, the neon atom has 10 neutrons
number of protons and neutrons (mass number)= 20
- number of protons (atomic number)= 10
number of neutrons= 10
-Mass as a number can vary among atoms of a single element
- All atoms of an element have the same number of protons but can have different numbers of neutrons
Example 2: Determining the Number of Particles in an Atom
How many protons, electrons, and neutrons are present in an atom of copper whose atomic number is 29 and whose mass number is 64?
1. Gather info
-The atomic number of copper is 29
- The mass number of copper is 64
protons= 29 64
electrons= 29 -29
35 neutrons
- Different elements can have the same mass number
- Knowing just the mass number does not help identify the element
Ex: Some copper atom nuclei have 36 neutrons (therefore mass number = 65) Zinc atoms have 30 protons and 35 neutrons
- Isotopes of an Element Have the Same Atomic Number
- Isotope- an atom that has the same number of protons (atomic number) as other atoms of the same element has a different number of neutrons (atomic mass)
- There are two standard methods of identifying isotopes
- Write the mass number with a hyphen after the name of an element (called hyphen notation; ex. Bromine- 80)
- Shows the composition of a nucleus as the isotope's nuclear symbol
- Nucleic Notation
Ex.
12
6
C C= element symbol
12= mass number
6= atomic number
Chapter 3
Section 3: Electron Configuration
I. Atomic Models
-After the atomic theory was widely accepted by scientists, models of atoms were constructed.
-Building a model helps scientists imagine what may be happening at the microscopic level
-Models have limitations
-Models are modified or discarded as new information is found
A. Rutherford's Model Proposed Electron Orbits
From section 2 J.J. Thomson proposed that the electrons of an atom were embedded in a positively charged ball of matter
Named the plum-pudding model because it resembled English plum pudding, a dessert consisting of a ball of cake with pieces of fruit in it
In 190, Rutherford performed experiments that disproved Thomson's model.
Rutherford envisioned the electrons outside the nucleus orbiting like planets orbiting the sun
Because opposite charges attract, the negatively charged electrons should be pulled into the positively charged nucleus
B. Bohr's Model Confines Electrons to Energy Level
Rutherford model was replaced two years later by a model developed by Niels Bohr, a Danish physicist
According to the Bohr model, electrons can be only certain distances from the nucleus
Each distance from the nucleus quantity of energy that an electron can have
The distance in energy between two energy levels is known as a quantum of energy
C. Electrons Act Like Both Particles and Waves
Thomson's experiments demonstarted that electrons act like particles that have mass
II. Electrons and Light
By 1900, scientists knew that light could be thought of as moving waves that have given frequencies, speed, and wavelengths
Wavelength- the distance between two consecutive peaks or troughs of a wave
units- meters
wavelength of light- 105 to less than 10-10 m
Electromagnetic Spectrum- all the frequencies or wavelengths of electromagnetic radiation
Einstein proposed that light has the properties of both waves and particles
Light can be described as a stream of particle, the energy of which is determined by the light's frequency
A. Light is an Electromagnetic Wave
When passed through a glass prism, sunlight produces the visible spectrum--all the colors of light that a human can see
B. Light Emission
When a high-voltage current is passed through a tube of hydrogen gas, lavender-colored light is seen
When this light is only made up of a few colors called LINE-EMISSION SPECTRUM
Each element has a line-emission spectrum that is made of a different pattern of colors
C. Light Provides Info About Electrons
Ground state- lowest energy state of a quantized system
Excited state- state in which an atom has more energy than it does as its ground state
If an electron gains energy, it moves from ground state to excited state
Chapter 3: Section 3
III. Quantum Numbers
Quantum model- present-day model of the atom in which electrons are located in orbitals
- Electrons within an energy level are located in orbitals (regions of high probability for findings particular electron)
To define the region in which electrons can be found, scientists have assigned four QUANTUM NUMBERS
Quantum Number- a number that specifies the properties of electrons
-principal quantum number (n)
-angular momentum quantum number (l)
-magnetic quantum number (m)
-spin quantum number (+ ½ or - ½) ( ↑ or ↓)
Principal Quantum Number (n) - indicates the main energy level occupied by the electron
-values are positive integers such as 1, 2, 3,and 4
-As n increases, the electron's distance from the nucleus and the electron's energy increases
Angular Momentum Quantum Number (l)- indicates the shape or type of orbital that corresponds to a particular sublevel.
Chemists use a letter code for this Number
l= 0 corresponds to an s orbital
l= 1 to a p orbital
l= 2 to a d orbital
l= 3 to an f orbital
Magnetic Quantum Number (m)- indicates the numbers and orientations of the orbitals around the nucleus
The value of m takes whole-number values, depending on the value of l
The number of orbitals includes on s orbital, 3 p orbitals, 5 d orbitals, and seven f orbitals
Spin Quantum Number (symbolized by + ½ or - ½ and by ↑ or ↓) - indicates the orientation of an electron's magnetic field
A single orbital can hold a maximum of 2 electrons, which must have opposite spins
A. An Electron Occupies the Lowest Energy Level Available
Pauli Exclusion Principle helps you to write an electron configuration for an atom
Aufbau Principle- electrons fill orbitals that have the lowest energy first
B. An Electron Configuration is a Shorthand Notation
The arrangement of the electrons can be shown by the nucleus's electron configuration
Sulfur has sixteen electrons:
1s2 2s22p6 3s2 3p4
Section 4: Counting Atoms
I. Atomic Mass
- Atoms are so mall that the gram is not a very convenient unit for expressing their masses
- Atomic Mass- the mass of an atom expressed in atomic mass units (amu)
II.Introduction to the Mole
- Mole- number of atoms in exactly 12 grams of carbon-12. It is the SI unit for the amount of a substance (
- Molar Mass- the mass in grams of one mole of a substance (g/mol)
- Avogadro's number- 6.022 x1023 The number of atoms or molecules in 1 mol.
3.50 mol Cu x 63.55 x g Cu
1 mol Cu
3.50 mol Cu x 63.55 x 1023 g Cu = 222 g Cu
1 mol Cu
II. Intro to the Mole
A. Chemists and Physicists agree on a Standard
In 1960, a standard was set based on an isotope of carbon
Defines atomic mass unit (amu) as one twelfth of the mass of one carbon-12 atom
One amu= 1.6005402 x 10-27 kg
you read this chemistry project at #ChemistryNotesInfo website http://chemistrynotesinfo.blogspot.in
Chemical-any substance that has a defined composition
Chemical reaction- the process by which one or more substances change to produce one or more different substances
States of matter-the physical forms of matters, which are solid, liquid, gas, and plasma
Reactant- a substance or molecule that participates in a chemical reaction
Product- a substance that forms in a chemical reaction
Matter-anything that has mass and takes up space
Volume-a measure of the size of a body or region in three-dimensional space
Mass-a measure of the amount of matter in an object; a fundamental property of an object that is not affected by the forces that act on the object, such as the gravitational force
Weight- a measure of the gravitational force exerted on an object; its value can change with the location of the object in the universe
Quantity- something that has magnitude, size, or amount
Unit- a quantity adopted as a standard of measurement
Conversion Factor- a ration that is derived form the equality of two different units that can be used to convert from one unit to the other
Physical property- a characteristic of a substance that does not involve a chemical change, such as density, color, or hardness
Density –the ratio of the mass of a substance to the volume of the substance; often expressed as grams per cubic centimeter for solids and liquids and as grams per liter for gases
Chemical Property- a property of matter that describes a substance’s ability to participate in chemical reactions
Atom- the smallest unit of an element that maintains the properties of that element
Pure Substance- a sample of matter, either a single element or compound, that has definite chemical and physical properties
Element- a substance that cannot be separated or broken down into simpler substances by chemical means’ all atoms of an element have the same atomic number
Molecule- the smallest unit of a substance that keeps all of the physical and chemical properties of that substance; it can consist of one atom or two or more atoms bonded together
Compound- a substance made up of atoms of two or more different elements joined by chemical bonds
Mixture- a combination of two or more substances that are not chemically combined
Homogeneous- describes something that has a uniform structure or composition throughout
Heterogeneous- composed of dissimilar components
Spectroscopy:- It deals with the study of interaction of electromagnetic radiations with matter.
Spectroscopy is interested in the study of interaction of electromagnetic radiations with chemical species, As a result of interaction, the energy of electromagnetic radiations is absorbed or emitted by the matter in discrete amounts ( photons or quanta ) and a spectrum is produced.
There are two principal classes of spectrum i.e. Absorption spectrum and Emission spectrum.
Types of Spectroscopy?
There are so many types of spectroscopy. Some of Important types are given below. Click on the name to get full detail of that spectroscopy.
1. Symmetry and Group Theory
2. Basics of IR Spectroscopy
3. Types of Spectra and Ultraviolet and Visible Spectroscopy
4. Microwave And Vibrational Spectroscopy
4.1. Microwave Spectroscopy
4.2. Infrared Spectroscopy
4.3 RAMAN Spectroscopy
5. Electronic Spectroscopy
5.1. Atomic Spectra
5.2. Molecular Spectroscopy
5.3. Photo Electron Spectroscopy
5.4. Photo Acoustic Spectroscopy
6. Magnetic Resonance Spectroscopy
6.1. Nuclear Magnetic Resonance Spectroscopy, NMR Spectroscopy
6.2. Electron Spin Spectroscopy
6.3. Nuclear Quadrupole Spectroscopy
7. Diffraction
7.1. X-Ray Diffraction
7.2. Electron Diffraction
7.3. Neutron Diffraction
Atomic Structure
What is an atom?
Matter found around us in nature (like iron rod, glass, cup, pen, pencil etc.) is made up from very small particles, which is known as atoms.
we also says that "atoms are very small particles which made matter" so atom is fundamental unit of atom.
Greek Philosopher, Democritus describe atom as very small indivisible particle.
'New System of Chemical Philosophy' is a book about atom written by John Dalton in 1703.
Dalton Atomic Theory
According to this theory atom cannot be divided, but after some years it is proved that atom can be divided further by many scientists like J.J.Thomson, L.Rutherford, N.Bohr, Chadwick etc.
Constituting particles of atom
Atom made up from 3 main particles-
1. Electron 2. Proton 3. Neutron
Discovery of Electron
Sir J.J.Thomson and W.Crooks did many experiments with discharge tube for the discovery of electron.
Discharge tube have tube like shape made from glass with two electrodes (Cathode -ve and Anode +ve) in vacuum created by vacuum pump connected to discharge tube. High electric potential is applied between two electrodes.
Discharge Tube
Air is bad conductor of electricity so vacuum pump is connected to reduce pressure to 0.02mm inside discharge tube currents starts flowing between electrodes and light is emitted. On further reducing pressure in discharge tube greenish yellow color fluorescence occur. As these rays emerging from cathode, Sir J.J.Thomson named them as cathode rays.
Deflection of cathode rays towards positively charged plate in electric field proves that these rays carry negatively charged particles.
These negatively charged particles are named as electrons.
Properties of Cathode Rays
1. Cathode rays always travel in straight line.
Production of Cathode Rays
2. Velocity of cathode rays and velocity of light are approximately equal.
3. On applying electric field in the path of cathode rays, cathode rays turn towards +vely charged plate that proves cathode rays are made up from negatively charged particles.
4. Cathode rays rotate light wheel placed in their path that proves cathode rays are made from particles having mass.
5. Cathode rays pass through thin metal foil and it gets slightly heated up by action.
6. These rays produce fluorescence at walls of glass tube.
7. Cathode rays ionize gases and also affect photographic plate.
8. When these rays strike any metal with high melting point (like tungsten W) they produces X-Rays.
What is X-rays?
X-rays are electromagnetic radiation , X-rays was discovered by W.K.Roentgen in 1895. X-rays are also known as Roentgen rays.
Why X-rays are used in medical sciences?
X-rays are used in medical sciences because x-rays have high penetrating power.
Determination of charge to mass ratio of electron (e/m)
J.J.Thomson conduct many experiments that charge to mass ratio of an electron remains same, irrespective of nature of gas and nature of cathode electrode material.
value of e/m = -1.76x108 coulombs/gram
Millikan's Oil Drop Experiment
Millikan's Oil Drop Experiment or Determination of charge of electron is conduct by an American Scientist R.A.Millikan, who perform an experiment on the charge on oil drops. R.A.Millikan perform several experiments to calculate charge on oil drops and he gets every time its value equal to -1.6x10-19 coulomb.When these results associated with results of cathode rays then conclude that charge present on particle of cathode rays is -1.6x10-19 coulomb.
Calculation of mass of electron
As we know e/m = -1.76x108 coulombs/gram
e = -1.6x10-19 coulomb
then,
(e/m)/e = (-1.76x108)/(-1.6x10-19)
so,
m = 9.102x10-28 gram
m = 9.102x10-31 kilogram
Mass of electron in comparison with atom
Mass of electron in comparison with atom is described below-
Mass of 1 mole of Hydrogen = 1.008gms
Number of hydrogen atom in 1 mole = 6.023x1023
Mass of 1 atom of hydrogen = 1.008/6.023x1023
= 1.67x10-27kg
Mass of electron is 9.109x10-31
then,
= Mass of 1 atom of hydrogen/Mass of electron
= (1.67x10-27)/(9.109x10-31) = 1837
so,
Mass of an electron is 1/1837 th the mass of a hydrogen atom.
Discovery of Proton
As we know electron is negatively (-vely) charged particle but atom is electrically neutral so there should be some particles which have positive (+ve) charge to neutralize negative (-ve) charge electron.
In 1886, a German scientist E.Goldstein established the presence of +vely charged particles. These positively charged rays travel from anode to cathode so called as anode rays or positive rays.
Why anode rays are called as canal rays?
Anode rays passes through canals or perforation in cathode so called as canal rays.
Properties of Anode Rays
1. Anode rays always travel in straight line.
2. Anode rays rotate light wheel placed in their path that proves anode rays are made from particles having mass.Which produces mechanical action.
3. On applying electric field in the path of anode rays, anode rays turn towards -vely charged plate that proves that anode rays are made up from positively charged particles.
Production of Anode Rays
Determination of charge to mass ratio of proton (e/m)
On the basis of many experiments performed for anode rays, scientist Wein concluded that charge to mass ratio of proton changes with change in nature of gases present in discharge tube. This value (e/m) is maximum for hydrogen gas = 9.58x104 coulomb per gram. "Positively charged particle of hydrogen is fundamental particle of matter that is called proton."
Charge on proton
Charge on proton is equal to charge on electron but is of opposite nature.
Charge on proton = 1.602x10-19 coulomb.
Mass of the proton
For hydrogen gas,
e/m = 9.58x104 coulomb per gram
charge of electron = 1.602x10-19 coulomb
so,
m = (e)/(e/m) = (1.602x10-19)/(9.58x104)
also,
m = 1.67x10-24 gram
m = 1.67x10-27 kg
so,
mass of proton is 1837 times more than mass of electron and is equal to mass of an hydrogen atom.
Discovery of neutron
Mass of atom is more than the mass of total proton and electron present in atom, which suggest the presence of another particle in atom which lead the discovery of neutron.
Chadwick in 1932 discover neutral particles of mass equal to mass of proton by bombarding beryllium metal with stream of fast-moving particles through cyclotron. These particles are neutral in nature so named as neutron.
Mass of neutron = 1.6748x10-27 kg
There is three fundamental particles in atom
These fundamental particles are 1. Electron 2. Proton 3. Neutron