1. Particles of Matter Have Space Between Them
2. Particles of Matter Are Continuously Moving
3. Particles of Matter Attract Each Other
Characteristics of Particles of Matter:
1.PARTICLES OF MATTER HAVE SPACE BETWEEN THEM :
we saw that particles of sugar, salt, Dettol, or potassium permanganate got evenly distributed in water. Similarly, when we make tea, coffee or lemonade (nimbu paani ), particles of one type of matter get into the spaces between particles of the other. This shows that there is enough space between particles of matter.
2 .PARTICLES OF MATTER ARE CONTINUOUSLY MOVING:
• Put an unlit incense stick in a corner of your class. How close do you have to go near it so as to get its smell?
• Now light the incense stick. What happens? Do you get the smell sitting at a distance?
• Record your observations.
• Take two glasses/beakers filled with water.
• Put a drop of blue or red ink slowly and carefully along the sides of the first beaker and honey in the same way in the second beaker.
• Leave them undisturbed in your house or in a corner of the class.
• Record your observations.
• What do you observe immediately after adding the ink drop?
• What do you observe immediately after adding a drop of honey?
• How many hours or days does it take for the colour of ink to spread evenly throughout the water?
• Drop a crystal of copper sulphate or potassium permanganate into a glass of hot water and another containing cold water. Do not stir the solution. Allow the crystals to settle at the bottom.
• What do you observe just above the solid crystal in the glass?
• What happens as time passes?
• What does this suggest about the particles of solid and liquid?
• Does the rate of mixing change with temperature? Why and how?
From the above three activities (1, 2 and 3), we can conclude the following :
Particles of matter are continuously moving, that is, they possess what we call the kinetic energy. As the temperature rises, particles move faster. So, we can say that with increase in temperature the kinetic energy of the particles also increases. In the above three activities we observe that particles of matter intermix on their own with each other. They do so by getting into the spaces between the particles. This intermixing of particles of two different types of matter on their own is called diffusion. We also observe that on heating, diffusion becomes faster. Why does this happen?
PARTICLES OF MATTER ATTRACT EACH OTHER :
• Take an iron nail, a piece of chalk and a rubber band.
• Try breaking them by hammering, cutting or stretching.
• In which of the above three substances do you think the particles are held together with greater force?
The above activity (1) suggest that particles of matter have force acting between them. This force keeps the particles together. The strength of this force of attraction varies from one kind of matter to another.
Explain why, we can easily move our hand in air but to do the same through a plank of wood, we need a karate expert.
Explain the following :
When an incense stick is lighted in the corner of a room, its fragrance spreads quickly in the entire room.
In which of the following conditions, the distance between the molecules of hydrogen gas would increase?
- increasing pressure on hydrogen contained in a closed container
- some hydrogen gas leaking out of the container
- increasing the volume of the container of hydrogen gas
- adding more hydrogen gas to the container without increasing the volume of the container
Which one of the following statements is not true?
- the molecules in a solid vibrate about a fixed position
- the molecules in a liquid are arranged in a regular pattern
- the molecules in a gas exert negligibly small forces on each other, except during collisions
- the molecules of a gas occupy all the space available