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The State of Matter

Posted by jibnhayyan on 27 July 2009

 

The States of Matter

The States of Matter

Everything in the universe that has mass and occupies space is made of matter. Matter exists in three physical states – solid, liquid or gas. There are three major states of matter: solid, liquid, and gas. A solid is something that has a definite shape and volume. A liquid has a definite volume but it takes the shape based on its container. A gas takes shape based on its container and it expands to fill the entire container.

A solid will keep its shape even when a force is applied to it, and  it will resist any attempt to alter its volume by applying pressure. The molecules in a solid are densely packed, held together by the strong attraction between them, and this gives the solid its characteristic form. These are the character of gas: high density, hard to expand/compress, takes shape of container.

A liquid, by contrast, will take on the shape of whatever container it is in, although its volume will remain constant. Its molecules are close enough together to retain a liquid form, but far enough apart that the liquid can move easily when a force is applied to it (for example, if it is poured or on a tilted surface where gravity will cause it to move).  However, if pressure is applied to a liquid, like a solid it will also resist any attempt to change its volume. These are the character of gas: high density, hard to expand/compress, takes shape of container.

A gas has no visible form (unless it is coloured, but even then it is very diffuse).  Its molecules are so far apart and moving so rapidly that it will expand as much as possible unless contained. Unlike solids and liquids, the volume of a given amount of gas will change with pressure – under pressure the volume will decrease, and the gas pressure pushing back on the walls of its container will increase as the gas molecules are forced closer together.  If the volume is increased then the pressure of the gas on the inside walls of the container will decrease, as the molecules have more room to move around.

These are the character of gas: low density, easy to expand/compress, fills container.

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Welcome to My Chemistry Class

Posted by jibnhayyan on 27 July 2009

At the beginning, I’d like to tell you about my ojectives in making this blog. It used to be the place for me and my students to share about our chemistry class. After contemplating for a long time, I plan to make to make this blog available for everyone who like to share about their chemistry class. Hope this blog can be very useful not only for my students but also for the other.

Let’s begin this chemistry class by answering this question, “What is Chemistry?”.

Chemistry is the science of substances, or materials, their composition and characteristics, and the reactions which take place between those substances. It is concerned with chemical elements in their pure state and when they are combined, that is, reactions of these elements and the compounds which they form.

Every chemical reaction can be represented with the help of atoms and molecules. It was really necessary, therefore, to develop a special system of chemical symbols. Substances in their pure state, called elements, were sometimes named after the scientists who discovered them. With the help of these chemical symbols, which contain both letters and numbers, chemical reactions can be described in a way which describes the reality of what takes place at the atomic level. Chemistry deals with reactions at the atomic level of substances. In turn, these secrets help chemists formulate chemical laws and scientific information, which help them to better understand the world around us. In our daily lives, chemistry can be found around every corner.

Chemistry at The Beginnings

Many chemical reactions and procedures were being used long before human beings figured out that chemical laws actually governed their behaviour.

The real beginnings of chemistry must be attributed to the developed cultures of times past. We can assume that the Egyptians, as well as the Chinese and ancient Greeks, were at the centre of the progress made in olden times. The inventions and discoveries made back then were often revolutionary, like the invention of gunpowder, which the Chinese discovered in the year 900 A.D. These discoveries often served to spark great progress in the field of natural sciences.

The ancient Greeks explained the nature of matter two different ways. Some claimed that all materials were made of four basic building blocks, or elements: air, water, earth and fire. Chemistry as a science had first to be founded from a philosophical perspective. The word alchemy as such means “black element”.

Antoine Lavoisier began the modern era of chemistry by proving the existence of “Oxygenia” through a combustion experiment. The 18th century saw scientific progress accelerated in an unprecedented fashion. New elements were discovered. The foundations of both electrochemistry and organic chemistry were laid. And, scientists began to try to organise matter, or the elements, in a systematic way. In the end, it was Mendel and Meyer who found the answer in what is now known as the periodic table of the elements, which is in use to this day.

New elements were discovered. The foundations of both electrochemistry and organic chemistry were laid. The discovery of molecular orbitals in the 20th century helped to explain covalent bonding. Thanks to that discovery, more and more synthetic products (artificially produced) were developed.

Important events in the history of chemistry

3200 B.C. Egyptian scientists produce copper from ore with the help of fire and wooden coal.

3000 B.C. First glass objects made in Egypt and Mesopotamia.

425 B.C. Democritus comes up with the first atomic theory in Greece.

300 B.C. Philosopher chemists formulate the first theory that all matter is made of elements (in Greece: 4-100 elements, in China: 5 elements).

180 B.C. First alchemistry experiments publicised in Egypt.

Around 600 years from the first Egyptian alchemistry attempts, the science reaches the Arab world.

900 A.D. The Chinese discover gunpowder.

Organised religion, specifically the Catholic Church, resists any and all new discoveries, keeping inventors and scientists from publicising their theories. The development of chemistry is greatly slowed, if not made completely impossible.

1661 Robert Boyle casts doubt on classical models and comes up with a new definition of the “element”.

1766 Henry Cavendish discovers hydrogen.

1782 Karl Sheele discovers oxygen, calling it the “spirit of fire”. Joseph Priestley comes up with the same discovery independently two years later.

1782 Antoine L. Lavoisier discovers that matter is neither created nor destroyed in chemical reactions, the law of conservation of mass.

1783 Antoine L. Lavoisier shows that oxygen and hydrogen can be burned together to form water.

1799 Joseph L. Proust shows that elements always combine in certain constant proportions of their mass (the law of constant proportions).

1803 John Dalton proposes his atomic model.

1807 Humphry Davy performs the first electrolysis separation, of table salt, into calcium and sodium.

1828 Friedrich Wöhler synthesises an organic resin from inorganic reactants.

1860 Robert W. Bunsen and Gustav R. Kirchhoff first discover an element, cesium, using spectroscopy.

1871 Dimitrij Mendel and Lothar Meyer publish their periodic table of the elements.

1884 Svante Arrhenius comes up with the theory of electrolytic dissociation.

1909 Sven Peter Srensen introduces the pH scale.

1920s Crystal structures begin to be investigated through X-ray structural analysis.

1937 Emilio Sergré synthesises the first man-made element – technecium.

1939 Linus C. Pauling introduces the first broad, modern theory of organic bonding.

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