Activity
1.4
Take two glasses/beakers filled with
water.
Put a drop of blue or red ink slow
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?
From this activity what we can conclude
Answers
Chapter: Chapter 1 – Matter in Our Surroundings
Class IX NCERT Science Text Book Chapter 1 Matter in Our Surroundings is given below.
As we look at our surroundings, we see a large variety of things with different shapes, sizes and textures. Everything in this universe is made up of material which scientists have named “matter”. The air we breathe, the food we eat, stones, clouds, stars, plants and animals, even a small drop of water or a particle of sand– each thing is matter. We can also see as we look around that all the things mentioned above occupy space, that is, volume* and have mass.
Since early times, human beings have been trying to understand their surroundings. Early Indian philosophers classified matter in the form of five basic elements – the “Panch Tatva”– air, earth, fire, sky and water. According to them everything, living or nonliving, was made up of these five basic elements. Ancient Greek philosophers had arrived at a similar classification of matter.
Modern day scientists have evolved two types of classification of matter based on their physical properties and chemical nature.
In this chapter we shall learn about matter based on its physical properties. Chemical aspects of matter will be taken up in subsequent chapters.
1.1 Physical Nature of Matter
1.1.1 MATTER IS MADE UP OF PARTICLES
For a long time, two schools of thought prevailed regarding the nature of matter. One school believed matter to be continuous like a block of wood, whereas, the other thought that matter was made up of particles like sand. Let us perform an activity to decide about the nature of matter – is it continuous or particulate?
Activity ______________ 1.1
Take a 100 mL beaker.
Fill half the beaker with water and mark the level of water.
Dissolve some salt/ sugar with the help of a glass rod.
Observe any change in water level.
What do you think has happened to the salt?
Where does it disappear?
Does the level of water change?
In order to answer these questions we need to use the idea that matter is made up of particles. What was there in the spoon, salt or sugar, has now spread throughout water. This is illustrated in Fig. 1.1.
NCERT Class IX Science Chapter 1 Matter in Our Surroundings
1.1.2 HOW SMALL ARE THESE PARTICLES OF MATTER?
Activity ______________ 1.2
Take 2-3 crystals of potassium permanganate and dissolve them in 100 mL of water.
Take out approximately 10 mL of this solution and put it into 90 mL of clear water.
Take out 10 mL of this solution and put it into another 90 mL of clear water.
Keep diluting the solution like this 5 to 8 times.
Is the water still coloured ?
NCERT Class IX Science Chapter 1 Matter in Our Surroundings
This experiment shows that just a few crystals of potassium permanganate can colour a large volume of water (about 1000 L). So we conclude that there must be millions of tiny particles in just one crystal of potassium permanganate, which keep on dividing themselves into smaller and smaller particles. Ultimately a stage is reached when the particles cannot divide further into smaller particles.
The same activity can be done using 2 mL of Dettol instead of potassium permanganate. The smell can be detected even on repeated dilution.
The particles of matter are very small – they are small beyond our imagination!!!!
1.2 Characteristics of Particles of Matter
1.2.1 PARTICLES OF MATTER HAVE SPACE BETWEEN THEM
In activities 1.1 and 1.2 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.
diffusion
Explanation:
the effect of diffusion could be seen both the beakers. Since diffusion depends in the density on the substance diffused , the beaker with ink gets diffusion within seconds and the beaker containing ink droplet takes longer hours of diffusion time.