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Monday, May 4, 2020

Matter

[Study material]Matter in our surroundings

There are a large number of things around us which we see and feel. For example, you can see this post in front of you. This post occupies some space. The space occupied by the ball is called its volume. If you pick up the ball, you can also feel its weight. So, you  conclude that the book has some mass. You cannot see the air around you, yet if you feel a balloon with year and  then weight it carefully, you will find that it not only  does Air occupy space ( bonded by the balloon), but it also has mass. Things like ball and air are example of matter. Other example of matter are wood, cloth, paper, ice, steel, water, oil, etc. further, that matter offers resistance in borne out by the fact that you cannot display an object from one place to another without applying some forces. You have to apply force to pick up a stone from the ground. On the contrary, light, heat, sound, electricity, etc., are not matter because they do not have any mass and they do not occupy space.
Example of Matter

        Thus, matter can be defined as follows.
Anything that occupies space, has mass and offers resistance is called matter.

 What is substance.

 A substance is a kind of matter that can’t be separated into other kinds of matter by any physical process. For example, sugar dissolved in water be separated from water by simply evaporating the water. Here, sugar is a substance which can’t be broken into its component by any physical process. Similarly, sodium chloride, lime (calcium oxide), etc., are all substances.

    Physical nature of matter.

1. Matter is made up particles

The ancient philosophers held the view that matter is continuous, like a block of wood. But this is not true. Actually, matter is made up of discrete particles. This can be easily e verified by performing the following activity.
     Take care a beaker. Fill half of it with water. Mark the level of water in the beaker. Address of sugar to the water and dissolved it with the help of a glass rod. You will see that the sugar has disappeared, but there is no change in the level of water. Can you say a where has the sugar gone? This can be explained by assuming that matter is not continuous,rather it is made up of particles. Sugar contains a large number of separate particles. These particles when dissolved in water occupies the space between the particles of water. That is why the water level in the beaker did not rise. Had sugar been continuous, like a block of wood, the water level in the beaker would have risen.
When a solid dissolves in a liquid, the volume of the liquid does not change

2. The particles of matter are too small to be imagined

This can be explained by performing the following activity.
Step 1 take some crystals of blue vitriol (copper sulphate) and dissolve them in 100 ml of water. The solution will go blue.
Step 2 take about 10 ml of the blue solution prepared in step 1. Add it to another hundred ml of face water.
Step 3 take about 10 ml of the solution prepared in step 2. Add it to another 100 ml of fresh water.
In this way, repeat the exercise 5 to 8 times. You will find that the last solution is a steel blue though the intensity of the colour has gradually decreased.
Just a few crystals of copper sulphate can colour a huge volume of water

This indicates that a few crystals of copper sulphate are able to colour and enormously large volume of water. This also shows that a small crystal of copper sulphate contains millions of small particles.

3. The particles of some matter are in constant motion

The following activity shows that the particle of some matter are always moving.
       Put an incense stick (agarbati) in a corner of your room. You can’t get it smell from a distance. For that, you have to move closer to it. Now, light the stick with a matchstick. You can now get its smell even if you are sitting at a distance. Why? The particles of perfume present in the incense stick freely mixed with the particles of air and have a speed across the room. Is the particles where not movie, the smell of the incense stick would never have recharged you.

4. The particle of matter attract each other

       The particles of matter are held Together by a force acting between them. This force is called intermolecular force of attraction.
      The strength of the intermolecular force of attraction differs from matter to matter.
Take an iron nail, a stick of Chalk and a small pieces of brick. Strike each of them separately with a hammer. You will observe that the stick of Chalk gets broken into pieces easily, the piece of brick brakes but not so easily, but it is most difficult to break the iron nail. What do these observations say? It is clear that the particles of iron nail are held Together by the strongest force followed by the pieces of brick, whereas the particle of Chalk have the weakest force of attraction.

5. The particle of matter have empty space between them

During the dissolution of sugar in water the particle of sugar occupy the important space between the particles of water. The Imperial space is called intermolecular space or intermolecular volume.
Intermolecular force and Intermolecular space

Tuesday, April 28, 2020

an iron almirah DJ solid at room temperature give two reason to justify

 an iron almirah is a solid because it has definite shape. You cannot flow it means it is solid.

water at room temperature is a liquid give two reason to justify

Water is liquid at normal temperature because it has no definite shape. It acquires the shape of the same container in which it is kept. Secondly it can flow easily. It means it is liquid not solid

we can get the smell of perfume sitting several metre away give reason

Particles of scent mix with the particle of air automatically and spread everywhere. Due to this scattering of particles a man sitting at some distance can a smell the scent

Naphthalene balls disappear with time without leaving any solid give reason

Naphthalene balls disappear without leaving any Residue because they are sublimated. In other words they are converted into gaseous state directly

why is ice at 273 K more effective in cooling than water at the same temperature

The energy of ice particles at 273 k A remains lower to the particles of water. As a result ice can absorb more energy from atmosphere this is the reason why being on equal temperature ice can cool more than water

Monday, April 27, 2020

what produce more Severe Burns boiling water or stream

At 373 K the energy of particles of vapour remains greater than the energy of particle of water at equal temperature. This happens due to the fact that particles of vapour absorb excess energy in form of latent heat of vaporization Hence when vapour comes in contact of a screen it is releasing energy more than the water boiling at the same temperature as a result steam produce more Severe burns than boiling water