properties of solids
solids can have different properties. for example some solids are hard while others are soft. some are dense while others are light. however all solids have some common properties. they
have a fixed volume have a fixed shape cannot be compressed and do not flow
rocks are solids because of these properties ( figure 1.1)
particles in a solids
are packed close together in an orderly arrangment
have little empty space between them and can vibrate but cannot move freely about their fixed positions.
changes of state that involve solids .
matter exists as solids liquid or gas. matter can change from one state to another the processes of change that involve solids include melting freezing and sublimation .
melting when a solids is heated the particles in it gain energy and vibrate more as the temperature increases the vibration of the particles also increases eventually the particles are able to overcome the forces that hold them in their fixed position. The solids then turns into a liquid . this is called melting .
the temperature at which a solids melts is called the melting point a pure substance has a fixed melting point. For example gold has a melting point of (1064 °C) it always melts at the same temperature . the melting points of some common substances are given in table 1.1.
what happens when a solid melts
the results of an experiment on the melting of a solid called stearic acid are plotted on a graph
(figure 1.3.) the temperature of the solids increases until it reaches 69 °C then the solids begins to melt. During melting heat energy is taken in by the particles of the solid to overcome the forces between the temperature remains constant ( line bc on the graph ) during the melting. This temperature is the melting point of stearic acid ( 69°C )