Page 94 - Innovator's Science-8

Science What do you observe in each case? Do the sand particles dissolve? Does the
Bytes
volume of water in the vessel change after mixing, and why?
Testimony Sand is a solid that does not dissolve in water.
When sugar is added to When added to water, the sand particles settle
water, it first raises the
water level slightly. But as down and occupy some space in the container,
a. Solid
it dissolves, the level causing the total volume to increase. What do you
decreases because the
ny sugar par cles fit into think about the interparticle spacing in solids? You
the small empty spaces learnt earlier that the constituent particles in solids
between the water are held together by strong forces of attraction. So, b. Liquid
par cles. This shows that
there are interpar cle these particles do not move from one place to
spaces in liquids. Other another and are closely packed. However, despite
soluble substances like
salt or glucose dissolve in close packing, some space is left between the c. Gas
Magnified schematic
the same way, while particles as shown in here. You might assume that pictures of interparticle
insoluble solids like sand the space between particles is filled with air, but space in the three states
do not - they simply se le of matter
down. In solids, the this is not the case. They contain nothing at all.
par cles are very closely
packed and held together HOW PARTICLES MOVE IN DIFFERENT STATES OF MATTER?
by strong forces of
a rac on, so they cannot Let us find out about the movement of particles in the three states of
move freely. In liquids, matter.
the par cles are less
ghtly packed and can • Take a glass tumbler containing water and
Glass
slide past one another, put a few grains of potassium tumbler
while in gases, the permanganate into it.
par cles are far apart and
move freely in all • What do you observe? Potassium
direc ons. Thus, the permanganate
spacing between par cles • Initially, you will see some streaks of pink (a) (b)
increases from solids to colour spreading out from the grain. a. Streaks of pink colour
liquids to gases, and this spreading out
explains the different • With the passage of time, the entire bulk b. Uniform pink
proper es of the three of water will acquire a uniform pink colour. colour in glass tumbler
states of ma er.
• Do you know why this happens? This happens because the water
particles are in constant motion.
First they pull out the particles of potassium permanganate from its grain,

and later they hit these particles so that they get spread throughout the
liquid. In the case of many substances, the constituent particles are held
together strongly that the water particles are unable to pull these out. Such

substances, like sand, are insoluble in water.
What happens when you light an incense stick in one corner of the room?

When an incense stick is burned in one corner of a room, you first smell the
fragrance nearby. Soon, the smell spreads throughout the entire room. This

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