4. The Particles of Matter Attract Each Other
There are some forces of attraction between the particles of matter which bind them together. The force of attraction between the particles of the same substance is known as cohesion. The force of attraction (or cohesion) is different in the particles of different kinds of matter. This will become more clear from the following examples.
If we take a piece of chalk, a cube of ice and an iron nail, and beat them with a hammer, we will find that it is very easy to break the piece of chalk into smaller particles, it requires more force to break a cube of ice, whereas the iron nail does not break at all even with a large force. This shows that the force of attraction between the particles of chalk is quite weak, the force of attraction between the particles of ice is a bit stronger whereas the force of attraction between the particles of iron nail is very, very strong.
Let us take another example. We can move our hand through air very, very easily because the force of attraction between the particles of air (which is a gas) is very, very small. It is negligible. We can also move our hand through water in a bucket fairly easily because the force of attraction between the particles of water (which is a liquid) is also small. But we cannot move our hand through a plank of wood because the force of attraction between the particles of wood (which is a solid), is very strong. And if we try breaking a plank of wood with a blow of our hand, our hand will get hurt. It needs a karate expert to move his hand through a plank of wood and break it into two. In general, the force of attraction is maximum in the particles of solid matter and minimum in the particles of gaseous matter. Let us solve one problem now.
Sample Problem. What happens to the sugar when it dissolves in water ? Where does the sugar go ? What information do you get about the nature of matter from the dissolution of sugar in water ?
Solution, (a) When sugar dissolves in water, its tiny particles break off from the solid 'sugar crystals'.
(b) The sugar particles go into the spaces between the particles of water and mix with them (to form sugar solution).
(c) The dissolution of sugar in water tells us that:
(i) the matter (here sugar and water) is made up of small particles.
(ii) the particles of matter (here water) have spaces between them.
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3. 2. Liquid to Gas Change : Boiling (or Vaporisation)
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4. 2. Latent Heat of Vaporisation (Liquid to Gas Change)
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5. Effect of 'Heating' and 'Cooling' on a Saturated Solution
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6. Classification Of Matter As Solids, Liquids And Gases
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9. Why Solids, Liquids and Gases Have Different Properties
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14. 2. The Particles of Matter have Spaces Between Them
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15. 1. Solid to Liquid Change : Melting
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16. 3. Gas to Liquid Change : Condensation
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20. 1. Latent Heat of Fusion (Solid to Liquid Change)
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24. 1. The Particles of Matter are Very, Very Small
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26. 4. The Particles of Matter Attract Each Other
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28. 3. The Particles of Matter are Constantly Moving
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29. Characteristics of Particles of Matter
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30. 4. Liquid to Solid Change : Freezing
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31. Two More States of Matter : Plasma and Bose-Einstein Condensate
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38. The Common Unit Of Temperature and Si Unit Of Temperatre
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39. To Show That Solids and Liquids Cannot be Compressed but Gases Can be Compressed Easily
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44. To Show that Liquids do not have a Fixed Shape but they have a Fixed Volume
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45. To Show the Presence of Water Vapour in Air
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49. Gases Can be Liquefied by Applying Pressure and Lowering Temperature
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50. To Show that Gases do not have a Fixed Shape or a Fixed Volume
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