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Thursday, December 3, 2009

Branches of Chemistry

There are several branches of chemistry. Here is a list of the main branches of chemistry, with an overview of what each branch of chemistry studies.


The science of chemistry is divided into

several disciplines or branches of chemistry.

Ryan McVay, Getty Images


Agrochemistry
- This branch of chemistry may also be called agricultural chemistry. It deals with the application of chemistry for agricultural production, food processing, and environmental remediation as a result of agriculture.

Analytical Chemistry - Analytical chemistry is the branch of chemistry involved with studying the properties of materials or developing tools to analyze materials.

Astrochemistry - Astrochemistry is the study of the composition and reactions of the chemical elements and molecules found in the stars and in space and of the interactions between this matter and radiation.

Biochemistry - Biochemistry is the branch of chemistry concerned with the chemical reactions that occur inside living organisms.

Chemical Engineering - Chemical engineering involves the practical application of chemistry to solve problems.

Chemistry History - Chemistry history is the branch of chemistry and history that traces the evolution over time of chemistry as a science. To some extent, alchemy is included as a topic of chemistry history.

Cluster Chemistry - This branch of chemistry involves the study of clusters of bound atoms, intermediate in size between single molecules and bulk solids.

Combinatorial Chemistry - Combinatorial chemistry involves computer simulation of molecules and reactions between molecules.

Electrochemistry - Electrochemistry is the branch of chemistry that involves the study of chemical reactions in a solution at the interface between an ionic conductor and an electrical conductor. Electrochemistry may be considered to be the study of electron transfer, particularly within an electrolytic solution.

Environmental Chemistry - Environmental chemistry is the chemistry associated with soil, air, and water and of human impact on natural systems.

Food Chemistry - Food chemistry is the branch of chemistry associated with the chemical processes of all aspects of food. Many aspects of food chemistry rely on biochemistry, but it incorporates other disciplines as well.

General Chemistry - General chemistry examines the structure of matter and the reaction between matter and energy. It is the basis for the other branches of chemistry.

Geochemistry - Geochemistry is the study of chemical composition and chemical processes associated with the Earth and other planets.

Green Chemistry - Green chemistry is concerned with processes and products that eliminate or reduce the use or release of hazardous substances. Remediation may be considered part of green chemistry.

Inorganic Chemistry - Inorganic chemistry is the branch of chemistry that deals with the structure and interactions between inorganic compounds, which are any compounds that aren't based in carbon-hydrogen bonds.

Kinetics - Kinetics examines the rate at which chemical reactions occur and the factors that affect the rate of chemical processes.

Medicinal Chemistry - Medicinal chemistry is chemistry as it applies to pharmacology and medicine.

Nanochemistry - Nanochemistry is concerned with the assembly and properties of nanoscale assemblies of atoms or molecules.

Nuclear Chemistry - Nuclear chemistry is the branch of chemistry associated with nuclear reactions and isotopes.

Organic Chemistry - This branch of chemistry deals with the chemistry of carbon and living things.

Photochemistry - Photochemistry is the branch of chemistry concerned with interactions between light and matter.

Physical Chemistry - Physical chemistry is the branch of chemistry that applies physics to the study of chemistry. Quantum mechanics and thermodyamics are examples of physical chemistry disciplines.

Polymer Chemistry - Polymer chemistry or macromolecular chemistry is the branch of chemistry the examines the structure and properties of macromolecules and polymers and finds new ways to synthesize these molecules.

Solid State Chemistry - Solid state chemistry is the branch of chemistry that is focused on the structure, properties, and chemical processes that occur in the solid phase. Much of solid state chemistry deals with the synthesis and characterization of new solid state materials.

Spectroscopy - Spectroscopy examines the interactions between matter and electromagnetic radiation as a function of wavelength. Spectroscopy commonly is used to detect and identify chemicals based on their spectroscopic signatures.

Thermochemistry - Thermochemistry may be considered a type of Physical Chemistry. Thermochemistry involves the study of thermal effects of chemical reactions and the thermal energy exchange between processes.

Theoretical Chemistry - Theoretical chemistry applies chemistry and physics calculations to explain or make predictions about chemical phenomena.

Wednesday, December 2, 2009

Analytical Chemistry

These are the techniques and applications of molecular identification. Analytical chemistry lecture notes, laboratory exercises, organizations, journals, software, and additional resources are provided. Information is available for calorimetry, crystallography, electrophoresis, chromatography, and spectroscopy.

Introduction to Qualitative Analys

Identifying Anions and Cations


Qualitative analysis is used to separate and detect cations and anions in a sample substance. In an educational setting, it is generally true that the concentrations of the ions to be identified are all approximately 0.01 M in an aqueous solution. The 'semimicro' level of qualitative analysis employs methods used to detect 1-2 mg of an ion in 5 mL of solution.

First, ions are removed in groups from the initial aqueous solution. After each group has been separated, then testing is conducted for the individual ions in each group. Here is a common grouping of cations:

Group I: Ag+, Hg22+, Pb2+
Precipitated in 1 M HCl

Group II: Bi3+, Cd2+, Cu2+, Hg2+, (Pb2+), Sb3+ and Sb5+, Sn2+ and Sn4+
Precipitated in 0.1 M H2S solution at pH 0.5

Group III: Al3+, (Cd2+), Co2+, Cr3+, Fe2+ and Fe3+, Mn2+, Ni2+, Zn2+
Precipitated in 0.1 M H2S solution at pH 9

Group IV: Ba2+, Ca2+, K+, Mg2+, Na+, NH4+
Ba2+, Ca2+, and Mg2+ are precipitated in 0.2 M (NH4)2CO3 solution at pH 10; the other ions are soluble

Many reagents are used in qualitative analysis, but only a few are involved in nearly every group procedure. The four most commonly used reagents are 6M HCl, 6M HNO3, 6M NaOH, 6M NH3. Understanding the uses of the reagents is helpful when planning an analysis.

Tuesday, December 1, 2009

Dalton's Atomic Theory

These are pretty straightforward and require no explanation. Although you don't use these on tests or anything, it's good stuff to know (not to mention our whole understanding of chemistry is based on this):

Each element is made up of tiny particles called atoms.
The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.
Chemical compounds are formed when atoms combine with each other. A given compound always has the same relative numbers and types of atoms.
Chemical reactions involve reorganization of the atoms--changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.
These ideas form the basis of what a lot of AP Chem is all about; chemical reactions. It's nothing more than breaking some bonds and making some bonds, to put the atoms in a different order to create new things.

Intro to Atomic Structure

An atom consists of a nucleus and electrons orbiting around it. The nucleus is made up of positively charged particles called protons, and neutral particles called neutrons. The electrons are negatively charged particles.

Here is a simplified picture:



This atom has two protons (red), so it is a helium atom.

One thing that pictures like the above cannot express is the relative sizes of the nucleus and the atom. If the atom was really that big (diameter 108 pixels), then the nucleus would be 1/100th of a pixel big! Or on a bigger scale, if the nucleus was the size of a pea, then the atom would be as wide as a football field. Another thing is mass. Virtually all the mass is concentrated in the nucleus. The 'pea' would weigh 250 million tons!

There are two numbers to know about any atom. One is the atomic number, which is the number of protons (and electrons in a neutral atom), and the atomic mass number, which is how much the thing weighs. One proton's weight is close to one neutron's weight which is close to one. Electrons weigh virtually nothing when compared to the huge protons, so they don't affect the total mass. So the atomic mass number is simply the number of protons plus the number of electrons.

The notation of writing atoms is like this:



The top number represents the mass number.

The bottom number represents the atomic number.

Some things to remember while solving these types of problems:

(Note: Problems of this simplicity will not be on the AP test, I guarantee that. We are not so lucky. But you will be tested in class on this stuff.)

The bottom number is always the number of protons.
The bottom number is also usually the number of electrons, but only in a neutral element. Ions come later.
The number of neutrons is always the top number minus the bottom number. All you're doing is taking the total mass, taking away the portion that is due to the protons, and what you got left is the neutrons. Likewise, if you know number of neutrons and protons, to find this number all you got to do is add.
Example:

Sample Problem


Here is a sample atom. How many electrons, protons, and neutrons does it got?

Solution

The bottom number is always the number of protons you have. So there are 9 protons. It's a neutral atom, by the fact that there are no plus or minus signs anywhere, so you can assume there are 9 electrons as well. There are 19 total nucleons (protons and neutrons) in the nucleus, and 9 are protons. So there are 10 neutrons. Easy.

Elements

As mentioned before, an element's mass is determined by its protons and neutrons. The electrons, having almost no mass, do no contribute to the mass of an element. An element is defined by the number of protons and electrons it has. The number of nuetrons an element has, however, can vary from atom to atom. Each possible atom is known as an isotope. (ex. Carbon-14) If you go look at a periodic table, you will notice that each element has a given mass. This mass is an average of its isotopes. This does NOT mean that all carbons will have 6 protons and 6 neutrons (don't worry about these calculations, they'll make sense in the next chapter). Just remember that an element can have different number of neutrons, which will change its weight.

Protons, neutrons, and electrons

Elements make up compounds, and are considered the basic building blocks of matter. You cannot break down elements into smaller parts, but you can classify the different parts within the element. Within the element are protons, neutrons, and electrons. The neutron, a chargeless particle, can be found in the nucleus along with the proton, which is a particle only slightly smaller than the neutron but positively charged. Electrons are negatively charged and are found circling the nucleus (much like the sun and the planets in our solar system).
Within the atom, one can find a nucleus. The nucleus, which does not move around like electrons, contains both neutrons and protons. Both neutrons and protons have mass, and these two contribute almost 100% of the atomic mass of an element. Electrons, on the other hand, have almost no mass. Most calculations assume a mass of zero for electrons. Electrons, being so small, can move around very quickly around the nucleus. Protons and neutrons can also be broken down into quarks, but you won't learn about those petit particles in this chemistry year.
A common demonstration to show how little space the electrons and nucleus take up in the atom is with the football field analogy. If a football stadium was considered to be an atom, a feather on the 50 yard line would be the nucleus. That is how much empty space there is within an atom!

Biochemistry

Biochemistry includes molecular, cellular, and organismal chemical activities. Metabolic pathways and enzymology, biochemical structures and sequences, and genome databases are included.







Biochemistry is the study of
the molecules of life, such as DNA.
Ben Mills



Biochemistry is the science in which chemistry is applied to the study of living organisms and the atoms and molecules which comprise living organisms. Take a closer look at what biochemistry is and why the science is important.

What Is Biochemistry?

Biochemistry is the study of the chemistry of living things. This includes organic molecules and their chemical reactions. Most people consider biochemistry to be synonymous with molecular biology.
What Types of Molecules Do Biochemists Study?
The principal types of biological molecules, or biomolecules are:



  • carbohydrates

  • lipids

  • proteins

  • nucleic acids


Many of these molecules are complex molecules called polymers, which are made up of monomer subunits. Biochemical molecules are based on carbon.


What Is Biochemistry Used For?


Biochemistry is used to learn about the biological processes which take place in cells and organisms.

Biochemistry may be used to study the properties of biological molecules, for a variety of purposes. For example, a biochemist may study the characteristics of the keratin in hair so that a shampoo may be developed that enhances curliness or softness.

Biochemists find uses for biomolecules. For example, a biochemist may use a certain lipid as a food additive.

Alternatively, a biochemist might find a substitute for a usual biomolecule. For example, biochemists help to develop artificial sweeteners.

Biochemists can help cells to produce new products. Gene therapy is within the realm of biochemistry. The development of biological machinery falls within the realm of biochemistry.


What Does a Biochemist Do?


Many biochemists work in chemistry labs. Some biochemists may focus on modeling, which would lead them to work with computers. Some biochemists work in the field, studying a biochemical system in an organism. Biochemists typically are associated with other scientists and engineers. Some biochemists are associated with universities and they may teach in addition to conducting research. Usually their research allows them to have a normal work schedule, based in one location, with a good salary and benefits.


What Disciplines Are Related to Biochemistry?


Biochemistry is closely related to other biological sciences that deal with molecules. There is considerable overlap between these disciplines:



  • Molecular Genetics

  • Pharmacology

  • Molecular Biology

  • Chemical Biology

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