Introduction To Chemistry (1949)

chemistry what is it what does it do for us how can we throughout the world in such industrial laboratories as this new products are discovered new chemistry is concerned with the structure of matter and how that structure can be changed in many ways our daily life is affected by the operations of such laboratories from lumps of coal chemistry produces nylon 4 hosiery and hundreds of purposes from raw petroleum synthetic rubber and a host of other products mold plant a powerful drug penicillin how can we study this science of street the answer to this question lies first in the way a chemist looked at the world about it of what is this world composed what is the composition the materials in the crust of the earth of the waters of the earth and the atmosphere around us in these the chemist sees first of all the element of which they are composed the pure states of matter are called element about 100 elements combine to form the millions of different substances in our world you're probably already familiar with some elements carbon nitrogen oxygen neon magnesium aluminum we divide the elements into two types according to the way they combine chemically about 3/4 of the element are called metals chemistry teaches us the relation between the properties all aluminium commonly uses for structural purposes iron for nails and many things copper for scouring pads and wire silver for spoons and tableware and gold as in jewelry on the other hand about 1/4 of the elements are classed as nonmetals and in general have different chemical characteristics from the metals non-metals include carbon as in coal phosphorus and the tips of Mac is sulfur seen here in its natural state and iodine used in disinfectants so there you have the two types of elements now most matter is made up of combinations of elements in the form of compounds or mixtures for example of the metals mercury is found as an element in nature aluminum is usually found as a natural compound and gold and silver often together as a natural mixture to obtain aluminum as a refined element it is necessary to separate it chemically from its naturally occurring compound from this refined aluminum various compounds such as aluminum chloride are made or the refined element may be mixed with other elements such as copper to make an alloy to understand more about mixtures and compounds let's take the element iron and mix it with the element sulfur when the two elements are thoroughly mixed what do we have in the beaker let's divide our sample into separate portions we'll have two portions in test tubes and one left in the beaker in the beaker with a magnet we can physically separate the iron from the sulfur because the iron retains its physical characteristic of magnetic attraction or we can use the solubility of sulfur in carbon disulfide and so physically separate the sulfur and iron in one of the tubes in another way the iron filings do not dissolve and are caught by the filter paper father dissolved sulphur flows into this evaporating dish when the solvent has evaporated we find tiny crystals of sulfur in the dish so we know we've been working with a mixture we have been able to separate the mixture physically into sulfur and iron now suppose we heat the remaining sample of the iron and sulfur mixture after a moment of heating the mixture begins to blow even after the tube is removed from the fire the glow continues this release of energy is one sign that a chemical reaction is taking place and when the test tube is cooled we can remove a black powder a solid what is this substance will the magnet effective no will it dissolve in our solvent of carbon disulphide no we have neither iron nor sulfur we have a new substance called iron sulfide not a mixture but a compound compounds have properties different from those of the elements they contain we have to use chemical means to separate a compound into its element let's take the compound mercuric oxide which can be separated into its original elements very readily by chemical means when heated strongly the mercuric oxide will decompose and after a moment tiny drops of mercury gather on the walls of the test-tube and what other element is being produced in this chemical reaction as this simple test shows it is oxygen the element which causes fuels to burn and is necessary to support all animal life until we have seen the formation of one compound and the decomposition of breaking down of another compound of the many types of compounds three are especially important for bases the acids and the salts let's see how these types of compounds interact first let's understand the acids for example sulfuric acid a compound of sulfur when acids react with certain metals in this case zinc we see the release of the element common in all acids hydrogen acids are made up of hydrogen combined with a nonmetal or of hydrogen combined with a group of elements which together have the chemical properties of a nonmetal then are the basis for example barium hydroxide bases often are compounds of metals containing hydrogen and oxygen hence the name hydroxide bases and acids react with one another neutralizing each other to form a third class of compounds the salts here barium sulfate we have learned some of the important ideas in chemistry and we have learned that chemistry is the study of elements compounds and mixtures we have seen examples of two types of elements metals and nonmetals we know that metals form basic compounds and nonmetals form acid compounds and when bases and acids neutralize each other a salt is formed with this background and with detailed knowledge of particular elements and compounds chemistry seeks answers to such questions as these what materials are light yet strong enough to be used in airplanes but various compounds and mixtures can be made from this sulfur what chemical and physical properties of this plastic make it so useful what chemicals can help cure diseases in mice and in human beings yes to these people chemistry is important it is their livelihood from research to production chemistry gives us benefits every day of our lives [Music]