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Chemistry: The Study of Matter What is Chemistry? The study of the matter, its composition, properties, and the changes it undergoes. A natural science. a language with its own vocabulary. a way of thinking. Review of matter: Matter: anything that takes up space (volume) and has a mass. Physical Properties: like different densities, melting points, boiling points, freezing points, color or smells Chemical Properties: A good example of chemical properties is the way elements combine with each other in reactions Review of states of matter Definite Definite Temperature Volume? Shape? increase Solid Liquid Gas YES YES NO Compressible? YES Small Expansion NO NO Small Expansion NO NO Large Expansion YES Condense Freeze Evaporate Melt Solid Liquid Gas Kinds of Change: physical change: no new substance is formed, properties such as size, shape, colour or state may change (eg. Boiling water) The reverse is possible chemical change: new substances (with new properties) are formed from 2 or more different elements. (eg. Rusting of iron) The reverse is not possible Properties Words that describe matter (adjectives) Physical Properties- a property that can be observed and measured without changing the composition of the substance. Chemical Properties- a property that can only be observed by changing the composition of the substance. Glossary: Pure substance: contains one type of particle. Ex: Elements and compounds: Mixture: contains two or more types of particles intermingling, no chemical bonding. Types are homogeneous and heterogeneous. Composed of two or more different atoms Can be broken down by chemical methods and each part will have different properties Examples: water (H2O), 2 atoms of hydrogen, I atom of oxygen) salt (NaCl), 1 atom of sodium, 1 atom of chlorine An element is a substance made up of only one kind of atom The periodic table arranges elements according to their properties Compound or Mixture Compound One kind of matterMolecule or atom Mixture More than one kind of matter- different molecules or atoms Made during a Made through a chemical change physical change Definite and uniform composition Variable in composition Which is it? Mixture Element Compound Heterogeneous 2 or more parts can be seen Different kinds of particles stay together. Mechanical mixing Ex: sand and salt, blood, milk Homogeneous Appear to be one substance Particles are intermingled May be solutions (something dissolved) Ex: air, salt water Solutions Homogeneous mixture with molecules mixed uniformly Solutions occur between any state of matter. Solid in liquid- Kool-aid Liquid in liquid- antifreeze Gas in a liquid – carbonated beverages Gas in gas- air Solid in solid - brass Liquid in gas- water vapor Solutions Like all mixtures, the components keep their own properties. Components can be separated by physical means Chemical symbols There are 112 elements Each has a 1 or two letter symbol First letter always capitalized second never Don’t need to memorize Some from Latin or other languages Chemical Reactions When one or more substances are changed into new substances. Reactants- stuff you start with Products- What you make NEW PROPERTIES Not easily reversed Indications of a chemical reaction Energy absorbed or released Color change Gas produced Precipitate- solid that separates from solution Not easily reversed ALWAYS THERE IS A NEW SUBSTANCE! Conservation of Mass Mass can not be created or destroyed in ordinary (not nuclear) changes. All the mass can be accounted for. What about nuclear? E = mc2 energy = mass x (speed of light)2 speed of light = 3 x 108 A little mass can make a lot of energy Law of Conservation of Mass - Energy the total of the mass and energy remains the same in any change Energy The ability to do work. Work - cause a change or move an object. Many types- all can be changed into the other. Types of energy Potential- stored energy Kinetic Energy- energy something has because its moving Heat- the energy that moves because of a temperature difference. Chemical energy- energy released or absorbed in a chemical change. Electrical energy - energy of moving charges Types of Energy Radiant Energy- energy that can travel through empty space (light, UV, infrared, radio) All types of energy can be converted into others. If you trace the source far enough back, you will end up at nuclear energy. Conservation of Energy Energy can be neither created or destroyed in ordinary changes (not nuclear), it can only change form. Its not just a good idea, its the law. Assigned reading: Page 6-8 and 10-16 Be able to define or explain the following terms/concepts Types of knowledge Pure/applied science Scientific method Rules of experimentation Laws, theories and models