Friday, January 24, 2020

HOW MANY STATES OF MATTER

We look at five states of matter on the site. Solids, liquids, gases, plasmas, and Bose-Einstein condensates (BEC) are different states of matter that have different physical properties. Solids are often hard, liquids fill containers, and gases surround us in the air. Each of these states is also known as a phase.
How does matter change from one state to another? Elements and compounds can move from one state to another when specific physical conditions change. For example, when the temperature of a system goes up, the matter in the system becomes more excited and active. If enough energy is pushed into a system, a phase change may occur as the matter moves to a more active state.
Let’s say you have a glass of water (H2O). When the temperature of the water goes up, the molecules get more excited and bounce around a lot more. If you give a liquid water molecule enough energy, it escapes the liquid phase and becomes a gas. The extra energy allows the molecules to change states.
Have you ever noticed that you can smell a turkey dinner after it starts to heat up? As the energy of the molecules inside the turkey heat up, they escape as a gas. You are able to smell the volatile compounds that are mixed in the air around you.

It’s About the Physical

"Phase" describes the physical state of matter. The key word to notice is "physical". Matter only moves from one phase to another by physical means. If energy is added (increasing the temperature) or if energy is taken away (freezing something), you can create a physical change,
Changing the pressure of a system is another way to create a physical change. If you place a glass of liquid water on a table, it will just sit there. If you place a glass of water in a vacuum chamber and lower the pressure, you can begin to watch the water boil and the water molecules move to a gas phase.

When molecules move from one phase to another they are still the same substance. There is water vapor above a pot of boiling water. That vapor (or gas) can condense and become a drop of liquid water in the cooler air. If you put that liquid drop in the freezer, it would become a solid piece of ice. No matter what physical state it was in, it was always water. Even though the physical state changed, the chemical properties were the same.
On the other hand, a chemical change would build or break the chemical bonds in the water (H2O) molecules. If you added a carbon (C) atom, you would create formaldehyde (H2CO). If you added an oxygen (O) atom, you would create hydrogen peroxide (H2O2). Neither new compound is anything like the original water molecule. Generally, changes in the physical state do not lead to any chemical change in compounds.

States of Matter Examples

Cartoon image of ocean wave.

A Liquid Ocean

There are many liquids around you. Oceans, lakes, and rivers are good examples of liquid water (H2O). Planetary scientists are looking for other planets that have liquid water, but planets require very specific conditions to have water as we know it.
Cartoon image of ceramic bowl.

Solids in Ceramics

Ceramic bowls are a great example of a solid. Did you know that pieces of pottery make up many of the items found from ancient civilizations? Ceramic materials are usually made from soft clay that is heated up and then slowly cooled. The clay becomes very hard because water (H2O) is removed and the chemical bonds inside the clay change.
Cartoon image of the Sun.

Plasmas on the Sun

Plasmas are highly energized gases that have lost their electrons. Stars, including the Sun, are covered in plasma. Hydrogen (H) and helium (He) ions float around the Sun with their electrons moving freely.
Cartoon image of balloons.

Gases in Balloons

Balloons aren’t technically gases. They are little pieces of rubber. However, the helium (He) inside the balloon is a gas. Helium is a noble gas that has a very low atomic mass. In its gaseous state, it is lighter than air. The helium atoms have a lower mass than the nitrogen (N2) and oxygen (O2) molecules that fill most of our air. The lower mass and lightness helps balloons to float.


Saturday, January 11, 2020

definition of quantum mechanics in chemistry

Definition of Quantum Mechanics Introduction

Classical mechanics does not provide an accurate description of matter on the scale of atoms and molecules. Electrons around a nucleus or nuclei do not behave like planets orbiting the sun or like ping-pong balls bouncing around in a container. Experiments show that when observing the properties of very small bits of matter, such as a single electron, the matter exhibits wave-like properties. Quantum mechanics is the mathematical description of matter on the atomic scale.
In chemistry we are mostly interested in the electrons that give atoms their properties and hold atoms together to form molecules. Thus to describe matter, and to predict the properties of molecules, we must use quantum mechanics . Terminology
  • operator - a series of mathematical steps.
  • Hamiltonian, h-hat - the operator that describes the energy of an electronic system.
  • wavefunction, psi.gif - a mathematical function that describes a wave-like shape.
  • eigenvalue - a value obtained from operating on a wavefunction.
The behavior of a quantum particle is completely described by the Schrödinger equation:
schrodinger.gif
A given Hamiltonian operator will have a series of wavefunctions that satisfy the Schrödinger equation. These wavefunctions are called eigenfunctions. The Hamiltonian operating on the eigenfunctions produces the eigenvalues, E, which are the allowed energies of the system.
For an illustration of how to use the Schrödinger equation see the one-dimensional particle-in-a-box.


CSIR-NET/JRF CHEMICAL SCIENCE NEW SYLLABUS

CSIR UGC NET NEW EXAM PATTERN AND SYLLABUS

CSIR UGC NET EXAM PATTERN-

Chemical sciences      Part A        Part B        Part C   Total

Total questions                                    20                           40                       60                  120

Maximum no of 
question to attempt                              15                          35                        25                    75

Marks for each
correct answer                                        2                          2                          4                   200

Marks for each
incorrect answer                                      0.5                      0.5                        1                     -
(negative marking)



The condidates are require to answer  maximum of questions 15,35,25 from each parts as given above .

       SYLLABUS- 

NOTE-

1 General Aptitude: 
  1. Part 'A' shall be common to all subjects. This part shall contain questions pertaining to General Aptitude with emphasis on logical reasoning, graphical analysis, analytical and numerical ability, quantitative comparison, series formation, puzzles etc.
  2. Subject Related: Part 'B' shall contain subject-related conventional Multiple Choice questions (MCQs), generally covering the topics given in the syllabus.
  3. Scientific Concept & Knowledge: Part 'C' shall contain higher order questions that may test the candidate's knowledge of scientific concepts and/or application of the scientific concepts. The questions shall be of analytical nature where a candidate is expected to apply scientific knowledge to arrive at the solution to the given scientific problem.
  4. Medium of Exam Language: The test will be in Hindi and English version. In case of any ambiguity between Hindi and English version due to translation, English version would be treated as final.
  5. If a candidate attempts more than the required no. of questions then only the First Set of required questions will be considered for scoring.

OFFICIAL LINK: https://csirhrdg.res.in/Home/Index/1/InPage/35/26