States of Matter

Matter is such a physical entity that has mass and occupies space. Usually, all matters can exist in three different states- solid, liquid and gaseous states. However, at normal room temperature some matters can exist as solids, some as liquids and some as gaseous. The state of a matter is changed with the change of temperature. They have their own characters and properties in all three states but no changes take place in their molecular structure. The molecules in solid state keep vibrating constantly staying very close to one another. These molecules get motion as they are heated and start moving away from one another. The solid, liquid and gaseous matters have the tendency of spreading in different media which may occur spontaneously or due to pressure.

Heat absorbed to heat released

Kinetic particle theory

Every matter is made of small particles and can exist in any particular state- solid, liquid and gaseous states. The particles of a matter remain kinetic in each state. We all know about the three states of water; ice (solid), water (liquid) and water vapor (gaseous). Changes in the three states of water have been shown in the following figure.

Changes in states of matter on heating

What will you observe when a cup of freshly boiled hot water is placed on a table. Particles of water vapor are spreading in air above the cup. If the cup were heated further, it would become empty at a certain time. But if the cup were left aside normally, it would cool down slowly; you could not have seen the water vapor being spread out. How the molecules remain in motion at solid, liquid and gaseous states is known from the kinetic theory of particles.

Boiled water in a cup

Solid has a fixed volume and definite shape. Molecules in solid remain very close to one another and keep vibrating due to the strong attraction force.

Liquid takes the shape of the container in which they are kept without changing their volume. Volume is slightly compressible with pressure. The motion of particles of liquid is higher than that of solid. The inter-molecular compulsion force is less than that in solid so the molecules in liquid remain at a moderate distance.

Gaseous substance can occupy the whole area of the container in which it is kept. Distances between gas molecules are large, as they have little attractive force. The particles of gaseous substance move freely. The molecules spread around with motion. Volume is highly compressible with pressure.

The kinetic energy of the molecules increases with increase of heat and they start moving fast. Molecules in liquid remain at large distance. On boiling gaseous molecules go out from the upper layer of liquid and gain sufficient energy as they can move around freely.

It is possible to transform a matter from one state to using heat energy on the basis of theory of kinetics. When solid is heated to its melting point it converts into liquid. When liquid is heated to its boiling point it converts to gaseous state.

Diffusion

Place a gas jar filled with air in the inverted position on another gas jar filled with freshly prepared ammonia gas by removing the lids, you will see that in the upper gas jar ammonia gas is mixed with air. To prove, enter a wet red litmus paper, it will turn blue.

Diffusion of gas particle in gas

Experiment-1

1. Take some liquid blue/ ink/ copper sulfate solution in a test tube.

2. Add water slowly using a dropper.

3. Observe the time required by whole water to become of the same color and take notes.

4. Now put another test tube in a beaker of hot water and take notes of the required time to occur the process no 3 after completing the process no 1 and 2.

Diffusion of solution particle in liquid

Experiment-2

1. Place a crystal of potassium per manganese in a test tube. Add water to it.

2. Note the required time of turning the whole water into light violet color.

3. Now put another test tube in a beaker of hot water and note the time required to complete the process no 1 and 2. Use a watch to record time.

You can do this experiment also with sugar, table salt. Though they are colorless, you have to taste them to observe weather the particles of sugar or salt have got mixed with water.

Diffusion of solid particle in liquid

What have you observed in test 1 and 2? More time is required before heating and less time is required after heating. The pace of spreading of the particles was higher in test 1 then comparing to test 2. Again the pace of spreading of the particle was higher in hot water than that of normal water. If we could do the test on gaseous substance (ammonia gas) by ourselves, we would see that, the rate of spreading of the particles much higher than that of the test 1. From the above experiments determine the relation of rate of diffusion with temperature.

In the above experiments no pressure is applied in any case.

The tendency of solid, liquid or gas to spread spontaneously and uniformly in any medium is called the diffusion.

Effusion

Take a balloon filled with helium gas or air. Make a small hole. Observe what happens. Within a very short time the balloon will be squeezed. Do you think why it happens so? The particles of gas or air went out through the small hole. Did any pressure work in this case? If any pressure worked, it would not be possible for the gas to spread spontaneously and uniformly. Small hole hindered the spontaneous movement of the molecules. The spontaneity increased with the increase of the size of the hole. When completely free from pressure it was converted to diffusion.

The pressure of helium gas inside and outside the balloon is not the same. The pressure inside the balloon is higher. The passage of gases from a region of high pressure to a region of low pressure through fine pores is called effusion.

For example, natural gas or methane gas (CH4) is converted to C.N.G (Compressed natural gas) by applying high pressure and used as fuel for vehicles. Methane gas and Butane and propane gas gathered from refinery are compressed in cylinders at high pressure to be used as household fuels. Oxygen gas is stored in cylinder at high pressure for clinical use. In case of any leakage in these cylinders, gas will burst out with high speed. That may cause a dangerous situation.

If a ripe jack-fruit is kept in a room of a house, the smell of jack-fruit comes out through the pores of jack-fruit skin and spread to other rooms. Coming out of smell through the pores of skin is effusion and spreading the smell to other rooms is diffusion.

Diffusion and effusion depends upon mass and density of the substance. As the mass and density of the substance increase, the rate of diffusion and effusion decrease.

Burning of Wax Candle and three states of matter

When candle burns, the three states of matter are observed together. When wax starts to melt, the thread of candle absorbs it. Wax turns to gaseous state at the top of the thread. We call it wax-vapor then it burns in presence of air. The candle keeps burning, as long as the thread exists. As the wax is a hydrocarbon i.e. an organic compound, carbon-die-oxide and water vapor is produced from the burning of wax in presence of sufficient air.

Burning of candle

Wax + O2(g) → CO2(g) + H2O(g) + Heat + Light

Melting and Boiling

Melting and boiling of a matter happened at specific pressure and temperature.

Experiment 1: Melting of matter

1. Take some grated wax in a heat proof glass tube and thrust the wax with a stick.

2. Arrange the apparatus and materials according to the figure. Tie the melting tube to the thermometer with a rubber band.

3. Apply heat slowly in low flame and stir the water of the beaker with a stirrer. Note the temperature at which the wax starts to melt. Remove the heat when it starts to melt. Note the temperature after every one minute.

4. In the experiment note the temperature from beginning to the end after every one minute using a watch.

5. Draw a curve, putting time in the X-axis and temperature in Y-axis of a graph paper and determine the melting point from it.

Melting of solid

Experiment 2: Boiling of matter

1. Arrange the apparatus and materials as shown in the figure. Make sure that the thermometer remains much above the water surface.

2. Heat until the water starts to boil. That is, stop heating when the water boils completely with bubble and water vapor comes out.

3. Maximum temperature has to be noted.

4. Note the temperature at every minute room beginning to end with a watch.

5. Determine the boiling point using a graph paper as done in experiment 1.

Boiling of liquid

At normal pressure (1 atm), the temperature at which a solid matter turns into liquid state is called the melting point of solid.

At normal pressure (1 atm), the temperature at which a liquid matter attains gaseous state is called the boiling point of liquid.

End

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