. Elementary physics and chemistry: first stage. Science. FiG. 8.—If a circular piece of paper is folded as shown by the dotted lines, it can be made into a cone which may be placed in a funnel for filtering. stone are also porous. In the kind of filter shown in Fig. 9 the water soaks through a block of carbon, and is thus purified. Things which will not allow water to pass or filter through them are called impervious. Clay is an impervious thing ; so is glass and india-rubber. Salt and —Salt and sugar are crystalline substances, that is, each small piece has a certain regular shape, wh
. Elementary physics and chemistry: first stage. Science. FiG. 8.—If a circular piece of paper is folded as shown by the dotted lines, it can be made into a cone which may be placed in a funnel for filtering. stone are also porous. In the kind of filter shown in Fig. 9 the water soaks through a block of carbon, and is thus purified. Things which will not allow water to pass or filter through them are called impervious. Clay is an impervious thing ; so is glass and india-rubber. Salt and —Salt and sugar are crystalline substances, that is, each small piece has a certain regular shape, which for a particular substance is always the same. Solids which take a regular shape like this are called crystals. You will learn more about these in a later lesson. Other common things which occur in crystals are washing-soda, borax, diamonds and some other precious stones, rock-crystal, and many other substances. Things which are not crystalline are called amorphous, a word which is made up of two Greek words meaning ' without shape.' Flour, soot, etc., are examples of amorphous things. Now, if you put the salt or sugar into a glass or bottle of water, and shake or stir the water, you will notice that the salt or sugar disappears, and if you taste the water you easily recognise the presence of the salt or sugar. You may say the salt or sugar has. Fig. 9.—A Filter in which the water passes through a block of car- bon, owing to the porosity of the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gregory, R. A; Simmons, A. T. London: MacMillan
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