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Matter in our surroundings refers to all matters that contain mass and occupy some space. Take a look at your surroundings and you see a wide range of things which come in varied shapes and sizes. All the material things we see around us are made of particles which in scientific terms, is known as Matter. For example: the book from which you study is made up of matter, so is your school bag, pencil and the food you eat. As long as the thing takes up space, has mass and can be perceived through our 6 senses, we can say that it is made up of matter.
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Definition and Composition of Matter
“Matter is used to cover all the substances and the materials from which the universe is made” - Matter is all around us and it comprises very small particles which are beyond our domain of imagination. The constituent parts of matter are atoms and molecules which can only be observed through a high powered microscope.
Matter in our Surrounding
Physical Nature of Matter in our Surrounding
Matter is made up of very tiny particles which in scientific terms we call atoms and molecules. Matter is not continuous but it is composed of minute particles which can be only observed by high powered microscopes. The universe is made of matter and everything we see around us is matter which comprises tiny particles. The arrangement and the energy possessed by these particles differ from one state of matter to another.
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Characteristics of Particles of Matter
- All matter consists of very small particles.
- These particles have intermolecular space between them. The space is not visible to the naked eyes
- These particles of matter are continuously moving,as they possess kinetic energy. The movement of the particles amplifies when the temperature rises, because the kinetic energy of the particles also increases.
- Particles of matter attract each other. There is a force acting between the particles which binds them together. The intensity of this force varies from one matter to another depending on its state.
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States of Matter
Predominantly, there are five states of matter which we see in our surroundings. This difference in state is due to the variation in the properties of the particle of matter.
The five states of matter are:
- Solid state
- Liquid state
- Gaseous state
- Plasma state
- Bose Einstein Condensates
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Solid
Solids have definite shape as the space between the particles in this state is negligible as they are firmly bound together and have distinct boundaries and fixed volumes. Solids are highly rigid and the particles only vibrate in their own positions as the kinetic energy is low. They neither flow nor diffuse.
Solids
There are a few exceptions:
- A rubber band is considered solid, but it changes its shape under force and recovers back to its original shape when the force is removed. When excessive force is applied, the rubber band breaks.
- Sponge is a similar example of solid which has tiny holes in which air is trapped and when compressed, the air is released and it gets compressed.
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Liquid
Liquids have no fixed shape and take the shape of the container in which it is transferred. But it has a fixed volume. Liquids flow and are not rigid, hence they are also called fluids. The kinetic energy in liquids is higher than solids and therefore the particles are not in any fixed position. Liquids do have more space between atoms than solids but that’s not enough to compress them, as they have a fixed volume.
Liquids
Gas
Gases neither have a definite shape nor volume. The kinetic energy is very high due to which the movement of the particles are unrestricted. They flow and diffuse rapidly. Since the space between the particles is large, they are also highly compressible.
Gas
Plasma State
Plasma is considered the fourth state of matter, which is comparable to the gaseous state. The state is obtained by heating a gas to a point when it loses all its electrons. It is a fused and ionic state of matter which is attained at very high temperatures like in stars and sun, which radiate as plasma is present in them. The fluorescent tube and neon sign bulbs consist of plasma.
Plasma State
Bose Einstein Condensates: (BEC)
The Bose-Einstein condensates were first thought by the Indian Physicist Satyendra Nath Bose in 1920, later Einstein predicted it as a new state of matter which is known as the Bose-Einstein condensates. The BEC is created by freezing a gas which has a very low density, so that the atoms break down into a single quantum state. This state is found at very low temperatures, when the kinetic energy is nearly negligible in the particles, so the movement is highly restricted to minimum.
Bose-Einstein condensates
Properties of Solid, Liquid and Gas
| Solid | Liquid | Gas |
|---|---|---|
| They have definite shape and volume. | They take the shape of the container but have definite volume. | They do not have a definite shape or volume. |
| The particles have the least energy. | Particles have higher energy than in solids. | Particles have the highest energy. |
| Solids are very rigid and cannot flow. | Liquids are comparatively less rigid and can flow easily. | Gases can flow freely in all directions and have no rigidity. |
| Solids have high density | Liquids have comparatively lower density than solids. | Gases have low density. |
| They are packed closely in a definite pattern. | They are loosely packed and don't have a definite shape. | They are poorly packed and can take up any space and escape easily. |
| The particles in this state only vibrate in their fixed position as the force of attraction is very high. | The particle in this state can move around freely within the set boundary, as the force of attraction between the particles is lower than solids. | The particles move in all directions freely as the force of attraction between particles is negligible. |
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Diffusion
“The mixing and spreading out of a substance with another substance due to the movement or motion of its particles is called Diffusion” - the process of diffusion continues till an uniform mixture is obtained. The most common example of diffusion is sugar or salt in water or the smell of perfume being perceived from the other end of the room.
Diffusion is higher in gases as compared to solids and liquids, as the particles of gases can move rapidly in all directions.
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Factors affecting Diffusion
- Density: The rate of diffusion is inversely proportional to the density of the gases and the liquids. Greater the density, smaller is the rate of diffusion.
(Gases diffuse rapidly and the rate of diffusion of a gas varies inversely to the square root of its density)
- Temperature: If the temperature rises, the rate of diffusion also increases, because the kinetic energy increases and the particles start moving rapidly.
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Effect of Change of Temperature
When the temperature of solids increases, the kinetic energy of the particles increases, due to which the particles start vibrating at a higher speed. The energy supplied outweighs the force of attraction between particles, which causes the atoms to leave their position and move freely. At a certain temperature, the solid melts to liquid. For example - ice melts into water at 0 degree celsius.Similarly, a liquid can change into gas on application of heat.
Similarly, on reducing the temperature or on cooling, the state of matter changes from vapour to liquid or liquid to solid.
Therefore, substances can change their state from one to another by changing the temperature.
- The process of changing the state of a substance from solid to liquid on heating is called Melting.
- The process of changing the state of a substance from liquid to a gas rapidly on heating is called Boiling.
- The process of changing a gas (or vapour) to a liquid by cooling is called Condensation.
- The process of changing a liquid (solidification) into a solid by cooling is called Freezing.
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Effect of Change of Pressure
Matter consists of atoms and molecules which have space between them. The space varies in different states of matter. When pressure is applied, this space reduces but in solids, the effect of pressure is negligible as the particles are firmly bound together. The effect of pressure on liquids is also pretty low as they have definite volume. The effect of pressure in gases is the highest, as the particles are wide apart moving in all directions. So, when pressure is exerted on gases, the atoms come closer, as the force of attraction between particles increases.
If the pressure exerted on gases is comparatively high, then the physical state can even change from gaseous to liquid and even the vice-versa is true, when the pressure decreases.
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Points to Remember
- Matter is anything that takes up space, has mass and can be perceived by our senses.
- There are mainly 3 states of matter namely - solid, liquid and gas.
- Diffusion is a phenomenon which is commonly seen in gases, as the particles in this state move rapidly in all directions.
- Density of a matter and temperature influences the rate of diffusion.
- By changing the temperature, substances change from one state to another.
- Changing a solid to a liquid is called melting.
- Changing a liquid to solid is called solidification.
- Changing a liquid to gas is called vaporization.
- Changing a gas to liquid is called condensation.
- Changing a solid to gas directly is called sublimation.
Sample Questions
Ques 1. What is the difference between solid, liquid and gas?(5 marks)
Ans. Differences are:
| Solid | Liquid | Gas |
|---|---|---|
| Has fixed shape and definite volume. | Takes the shape of the container but has definite volume. | Has no definite shape or volume. |
| It has high density and is not compressible. | Its density is lower as compared to solids but is not easily compressible. | It has low density and is easily compressible. |
| Solids do not flow. | Liquids flow easily | It flows freely. |
| Solids expand only slightly on heating. | Liquids expand more than solids on heating | Gases expand considerably |
Ques 2. Give 3 reasons to justify that wood is solid. (3 marks)
Ans. Wood is solid because -
- It has a definite shape.
- It has a definite volume
- It is not compressible and cannot flow.
Ques 3. Why are gases kept in air-tight gas cylinders? (2 marks)
Ans. Gases do not have definite shape or volume and it fills the entire container in which it is kept. Since it is a fluid, gases do not require a container for storing. But if gases are not kept in a container, it will escape as the particles move rapidly in all directions. This is why gases are usually kept in air-tight gas cylinders.
Ques 4. Why do we see water droplets on the outer surface of a glass containing ice-cold water? (1 mark)
Ans. The water vapour present in air, on coming in contact with the cold glass of water, loses energy and gets converted to liquid state, which we see as water droplets.
Ques 5. Arrange the following substances in increasing order of forces of attraction between the particles— water, sugar, oxygen. (1 mark)
Ans. Oxygen, water, sugar
Ques 6. What is the physical state of water at— (a) 25°C (b) 0°C (c) 100°C ? (1*3= 3 marks)
Ans. The states are:
- Liquid state
- Solid state
- Gaseous state
Ques 7. Why is ice at 273 K more effective in cooling than water at the same temperature? (3 marks)
Ans. To achieve room temperature, the ice at 273 K will absorb latent heat as well as thermal energy. Water at a temperature of 273 K would just absorb heat energy to achieve room temperature. Thus, water at 273 K will absorb less environmental heat energy than ice at 273 K. Therefore, ice at 273 K is more effective in cooling than water at the same temperature.
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Ques 8. Name the factors that affect evaporation. (4 marks)
Ans. The factors are:
- Temperature - the rate of evaporation increases on increasing the temperature and vice-versa
- Surface area - the rate of evaporation increases on increasing the surface area of the liquid.
- Humidity - when the humidity in the atmosphere increases, the rate of evaporation reduces.
- Wind speed - the rate of evaporation increases when the wind speed increases.
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