What is graphite? Unlike the tetrahedral arrangement of atoms in diamond, the carbon atoms in graphite are arranged in the form of hexagonal rings in layers (Fig.10.2). Each carbon is bonded to only three other carbon atoms in that layer. Different layers of graphite are held together by rather weak forces. Hence they can slide […]
WHAT IS ACIDS, BASES AND INDICATORS? All the elements in nature fall into three classes: metals, non-metals and gases. Non-metals are also sometimes called metalloids. The compounds formed by combination of the elements can also be classified as organic and inorganic compounds. Organic compounds are formed from a combination of carbon and hydrogen; they are
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What is Carbon monoxide?. Carbon monoxide is an odourless, tasteless and colourless gas, which is insoluble in water. It is extremely poisonous. Under no circumstances must the gas be inhaled or smelled. It is not usually prepared in a school laboratory. If need be, the gas should be prepared in a fume chamber. Preparation of
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Sodium Carbonate (Na2CO3) Popularly known as washing soda or soda ash, sodium carbonate is a commercially important compound. In earlier days, it was obtained from the ash of plants and from natural deposits in India and Egypt. Manufacture of Sodium Carbonate Raw Materials Sodium chloride – NaCl (brine solution) Ammonia – NH3 Limestone – CaCO3 (for
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Characteristics of periods The first period starts with hydrogen (H) and ends with helium (He). It has just two elements H (Z=1) and He (Z = 2). H has one electron in the first-shell. He has 2 electrons in the first-shell. As we have seen in the chapter on the structure of atoms, the first-shell
Ionic (Electrovalent) Bonding Noble gases like neon or argon have eight electrons in their outer shells (or two in the case of helium). These noble gas structures are thought of as being in some way a “desirable” thing for an atom to have. When other atoms react, they try to organize electrons such that their
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Silicon dioxide Has a high melting point – varying depending on what the particular structure is (remember that the structure given is only one of three possible structures), but around 1700°C. Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs. Is hard. This is due to the need to
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Diamond Has a very high melting point (almost 4000°C). Very strong carbon-carbon covalent bonds have to be broken throughout the structure before melting occurs. Is very hard. This is again due to the need to break very strong covalent bonds operating in 3-dimensions. Doesn’t conduct electricity. All the electrons are held tightly between the atoms,
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The higher the metal in the reactivity series the more reactive the metal with water. The following experiments show the reaction of metals with cold water and water vapour/steam. Reaction of sodium/ potassium with cold water: Procedure Put about 500cm3 of water in a beaker. Add three drops of phenolphthalein indicator/litmus solution/universal indicator solution/methyl orange indicator
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Physical properties Hydrogen is a neutral, colourless and odourless gas. When mixed with air it has a characteristic pungent choking smell It is insoluble in water thus can be collected over water. It is the lightest known gas. It can be transferred by inverting one gas jar over another. Chemical properties. Burning Hydrogen does not
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Occurrence Hydrogen does not occur free in nature. It occurs as Water and in Petroleum. School laboratory Preparation Procedure Put Zinc granules in a round/flat/conical flask. Add dilute sulphuric(VI) /Hydrochloric acid. Add about 3cm3 of copper(II)sulphate(VI) solution. Collect the gas produced over water as in the set up below. Discard the first gas jar. Collect
Hydrogenation/Hardening of unsaturated vegetable oils to saturated fats/margarine. When Hydrogen is passed through unsaturated compounds in presence of Nickel catalyst and about 150oC, they become saturated. Most vegetable oil are unsaturated liquids at room temperature. They become saturated and hard through hydrogenation. In weather forecast balloons. Hydrogen is the lightest known gas. Meteorological data is
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EVAPORATION AND BOILING (LIQUID TO GAS) On heating particles gain kinetic energy and move faster. In evaporation and boiling the highest kinetic energy molecules can ‘escape’ from the attractive forces of the other liquid particles. The particles lose any order and become completely free to form a gas or vapour. Energy is needed to overcome
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It is interesting to note that atoms of a given atomic number can have different number of neutrons. Atoms of elements having the same atomic number with different mass numbers are called isotopes Some examples are listed below: Isotopes of Hydrogen Hydrogen atom (Z=1) has no neutrons. Number of protons = 1 Number of electrons
Dmitri Mendeleev is credited as being the Father of the modern periodic table. In 1869 he arranged the 50 or so known elements in order of atomic number, Z, putting elements with similar properties in the same vertical group, and leaving gaps for unknown elements, yet to be discovered. When the elements were later discovered,
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The structure of the atom When scientists started exploring matter, they realized that matter can be divided into smaller and still smaller particles. They called the smallest particle an ‘atom’. The name ‘atom’ was derived from the Greek word ‘atoms’, meaning ‘indivisible’. They discovered that the ‘atom’ maintains its chemical identity through all chemical and
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As you go down the group from one element down to the next the atomic radius gets bigger due to an extra filled electron shell. The outer electron is further and further from the nucleus and is also shielded by the extra full shell of negative charge, therefore the outer electron is less and less
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Going down Group 2: There are more filled energy levels between the nucleus and the outer electrons, therefore the outer electrons are more shielded from the attraction of the nucleus So the electrons in the outer energy levels are further from the nucleus and the atomic radius increases. As the number of protons in the
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Chemistry is a branch of Science. Science is basically the study of living and non-living things. The branch of science that study living things is called Biology. The branch of science that study non-living things is called Physical Science. Physical Science is made up of: Physics- the study of matter in relation to energy Chemistry–
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Water is an important item in our universe. We need water for transport (lakes and oceans), Generation of power, (hydroelectricity), drinking industrial processes, manufacturing and cooling among others. Very little of the world’s water is fresh (2.6%). Most of it (97.4%) is in oceans. Most of the fresh water is frozen (76%). Only a tiny