Some Properties of Matter. Грекова О.А. - 13 стр.

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   6) Is there any limit to the height that             temperature can reach?
   7) What is the 1st law of thermodynamics?
   8) Is it possible to convert work into heat and on the contrary, work into heat? What is the
      main condition?
   9) What is the 2nd law of thermodynamics?
   10)What is the conservation of energy?

                                                    V
        There are three ways in which heat may pass from one point to another, termed
conduction, convection, and radiation, all three of which are observed in everyday life.
        If one part of a solid be made hot, the heat passes along it and raises the temperature of
the other parts. This is particularly noticeable with metals: with an all–metal pot containing a
hot liquid the handle gets hot, and if one end of a metal rod be heated in any way the other end
soon becomes hot. The effect is particularly strong with copper and silver, less noticeable with
lead. A measure of the effect of heat conduction is given by the quantity known as thermal
conductivity. This is the amount of heat, in calories, passing through unit area (1 square
centimetre) when the temperature falls 1 o C in a distance of 1 centimetre.
        Not only do metals conduct heat, but so do all other substances. For liquids and gases
there is a different method by which heat can pass from one point to another. Hot liquid can
move bodily from a hotter place to a colder place: even if it is not stirred in any way the hotter
liquid, having expanded, and so become lighter, will move up through the colder liquid,
carrying heat with it. This process is known as convection and takes place in gases as well. It is
a common fact of observation that hot air rises from a hot body. Whenever a liquid or a gas is
heated from underneath convection is very active in causing the passage of heat.
        Liquids and gases conduct heat also, but very badly. There are certain solids which
conduct heat particularly badly, owing to the fact that they consist mainly of tiny cells in which
air is imprisoned so that it cannot circulate and convey heat by convection. An example of
such a very poor conductor of heat is balsa wood, which is extremely light.
        The heat of the sun does not reach us by conduction or convection, but by the third
method, radiation. Rays from the sun, which have travelled through 92 million miles of empty
space before reaching the earth’s atmosphere, convey heat to every body on which they fall.
The light rays, which are partly absorbed by the surface, are responsible for some of the heat,
but more is conveyed by rays that behave like light rays but cannot be seen, called infra-red
rays.

   III Grammar:
                                 Comparatives and Superlatives.
   Use:
   a) The comparatives and superlatives of words with
          - one syllable are formed like this: green – greener – the greenest
          – with three syllables: beautiful – more beautiful – the most beautiful
   b) There are a few reliable rules for words with 2 syllables – you must learn them
   individually.
   c) Words ending in -‘y’ or -‘ow’ are usually written like one-syllable words. Words ending
   in –‘ful’ take ‘more’ and ‘most’.
   d) Note: -y – ier – iest


IV Writing: