The_Biology_Notes

Chemistry ‘The chemical Earth’, [pic] There are four main zones in the Earth: Lithosphere Atmosphere Biosphere Hydrosphere [pic] The Lithosphere comprises the crust and mantle. Scientists use this Lithosphere to gain mineral and organic resources. [pic] The Atmosphere is an envelope of gases that surrounds the Earth in white clouds surrounding the atmosphere consisting of water vapours. [pic] The atmosphere is made up of O2, N, CO2, and a little argon, Ne, krypton, xenon and radon. [pic] The Hydrosphere consists of the oceans, lakes, streams, glaciers, snow, ice and polar sheets and glaciers. [pic] The Earth is a closed sphere that means that matter cant enter or leave the Earth’s spheres. [pic] Matter classified at room temp (25C) as: Solid Liquid Gas [pic] Most of the 109 elements are solid [pic] There are two liquids at room temperature: Bromine (Non-metal) Mercury (metal) [pic] Kenetic Molecular Theory of Matter says that all matter is made up of particles that are constantly moving. [pic] Solids and liquids are LOW energy [pic] Gases are HIGH energy [pic] To separate a mixture of: Solids of different sizes- Sieving Magnetism Solids and liquids Filtration Boiling To obtain solid from a Evaporation Dissolved solid and Liquid To obtain the liquid Distillation From a dissolved solid And liquid Oil and water Separation funnel Ethanol and water Fractional distillation [pic] Chemical analysis is a process used to determine what is present in a chemical sample. This can be Qualitative Quantitative [pic] Qualitative Determines what substances are present in a sample [pic] Qualitative Determines how much of each substance is present in the sample [pic] Gravimetric analysis is used to determine the mass of each component in a mixture. Gravimetric analysis is used to determine the percentage composition of a mixture. [pic] Instrumental Analysis determines minor and trace amounts of elements down to 1% [pic] An example of an Australians scientist using Gravimetric analysis is Melina Key Wood, an environmental CSIRO scientist. [pic] Examples of industrial Gravimetric analysis include: Nutritional labels Soil analysis [pic] Element one type of atom with definite properties that cannot be decomposed [pic] Compound made up of two or more atoms with a definite property. [pic] The nucleus is the center of the cell used to produce chemical energy and nuclear energy eg in a power plant. [pic] The atomic number equals the same number as protons and electrons [pic] The mass number= protons + neutrons [pic] Ion is formed when atoms lose or gain their electrons. [pic] Ionic compounds are formed when oppositely charged Ions are attracted and held together by electrostatic forces called Ionic bonds. They are arranged in a lattice of infinite array [pic] Ionic crystals are neutral because the (+) charge cancels out the (-). [pic] Lewis electron dot diagrams only show electrons in the outer most shell [pic] The more reactive an element is, the more unlikely the chance of finding it existing alone [pic] There are two important trends presented in the Periodic Table Increasing atomic number left to right along rows Elements in same column have similar properties. [pic] History of the Periodic Table 330 BC Aristotle Four-element theory 1770 Lavoisier Distinguished first 33 elements 1828 Berzelius Table of atomic weights; element symbols 1829 Dobereiner ‘triad’ of elements with similar properties 1864 Newlands first sixty elements established and arranged 1869 Meyer Molars and atomic weights 1869 Mendeleev Created the ‘Periodic table’ and predicted gaps 1894 Ramsay Discovered noble gases [pic] Metal atoms lose electrons to form positive ions called cations [pic] Anions are when atoms gain electrons to form negative ions [pic] Ionic Compound formula shows the simplest ratio of the number of positive and negative ions with no subscript [pic] Empirical formulas show only the simplest ratio of atoms and not the actual ratio [pic] Radicals are a charged group of atoms AKA polyatomic ions and the bracket is placed around it to emphasise the charge [pic] The only positive radical is ammonium [pic] Valency is the combining power of an atom- the number of electrons an atom gains or loses to become a compound [pic] Eg: Aluminum Chloride Al3 Cl1 AlCl3 [pic] A molecule is the smallest part of a pure substance that can exist on its own and move independently and found in any desired number [pic] A monatomic molecule is made up of only one atom eg Noble gases [pic] Diatomic molecules are two atoms bonded together eg O2 and H2 [pic] Covalent bonds form between metals and nonmetals, because non-metals need to gain an electron to complete their shell [pic] Single covalent bond one pair of shared electrons moving around the nucleus of both atoms [pic] Double covalent bond- two pairs of shared electrons moving around the nucleus of both atoms [pic] Covalent molecule is held together by the electrostatic attraction between the shared pair of electrons and the protons of the atoms that share electrons [pic]Physical change is when no new substance is produced. The changes are: Easily reversed Relatively small amount of energy required An example is burning Mg ribbon to form a powder [pic] Chemical change is when a new substance is created: Gas evolved Precipitate forms Change in colour Change in temperature Disappearance of solid Odour produced An example is electrolysis [pic] The law of conservation says that matter cannot be created or destroyed by change form [pic] Electrolysis is a chemical change brought about by passing electricity through water to which a small amount of sulfuric acid had been added to improved conductivity. [pic] A commercial use of electrolysis is the molten lead bromine (PbBr) [pic] |Electrolysis |Boiling water | |Produces two new substances (O and H) |Produces no new substance | |Difficult to reverse |Easily reversed | |Requires more energy |Little energy required | |Breaks up the particle |Merely separates the particles from one another | [pic] Decomposition reactions are chemical reactions where a chemical is broken down into two or more substances. During the reaction, energy must be absorbed to break the tightly held bond. Thermal Light Electricity [pic] The stronger the bond, the more energy required to break it [pic] A commercial use of decomposition is cement and glass. [pic] Thermal decomposition reactions use the heat to break the bond and involve the use of a carbonate [pic] Light decomposition reaction eg photography. Thin plastic with AgBr on it is photo film, and when light hits the paper, the resulting reaction causes a bromine atom and a silver atom to form. [pic] Electrical decomposition reaction eg Aluminum extraction. Electricity is passed through Aluminia (Al2O3) to extract aluminum [pic] Synthesis reactions are where a chemical compound is formed from its elements (the opposite of decomposition) [pic] During synthesis reaction, bonds are formed and energy is released. [pic] Metals are arranged in an orderly lattice, and each atom releases an electron to become positive. The electrons released become delocalised and this becomes metallic bonding. Conduct Their electrons are delocalised and free to move throughout the lattice Hard the bonds are strong Malleable because del. Electrons easily adjust to new arrangement High m.p A lot of energy is required to break down bonds [pic] Ionic substances form when a non-metal reacts with a metal, and the metal become positive and the non-metal become negative, arranged in a lattice. The attraction between + and – ions is a strong ionic force holding substance together Not C. The ions are held together toughly in lattice and unable to move toward electrode Hard strong ionic bond Brittle A distortion of lattice when hit, so the ions repel off each other High m.p bonds are strong [pic] Covalent molecular substances formed when non-metals react to form a compound. N. Con. No delocalised ions to form a current Soft solids Easy to be distorted because of weak intermolecular forces between molecules Low. Mp The bonds to be broken down by heat are very weak and easy to overcome. [pic] Covalent network substances formed when non-metals react, and arranged in a lattice held together by covalent bonds (not charges). Eg silicon dioxide and diamond N.Con no delocalised electrons to form a current Hard covalent bonds cannot be distorted High mp strong bond to break by large amount of heat