Introduction
Everything in our surroundings are known as matter. They may be the food we eat, the vehicles, the gadgets, the day to day materials that we use, the air we breathe or the water that we drink. All of these things occupy some space and have mass and volume. For instance, in classrooms the benches that the students use to sit occupy, some space of the classroom. They have mass and volume and hence they can be regarded as matter.
According to the Indian philosophers matter can classified into five primitive elements. They are also known as Pancha Tatva– air, soil, fire, and water. Every living or non-living is made up these five primitive elements.
In this cartoon the bench is made of wood that comes from trees grown in soil in the presence of air. It requires heat, water for production. Therefore every matter directly or indirectly is made of Pancha Tatva.
Properties of matter
We all know that matter is composed of some very small particles called atoms that sum up together to form molecules which in turn gives rise to matter. These particles of matter possess some properties as follows:
- Matter is made up of particles
- The particles of matter are very small in size.
- The particles of matter have space between them.
- The particles of matter are continously moving.
- The particles of matter attract each other.
Experiments that proves properties of matter
The properties of matter can be proved using a simple experiment form our day to day life.
EXPERIMENT I:
- Take a glass filled with water and mark the level of water in the glass.
- Add sugar to the water in the glass.
- As soon as we add the sugar the level of water rises from the marked line.
- Take a stirer and keep on stiring the solution. After some time sugar gets dissolved and level comes back to its original marked line.
- This experiment proves that matter are made up of tiny particles due to which the particles of sugar adjsuted themselves into the spaces available between the tiny particles of water.
- This phenomenon of intermixing of particles of two different types of matter on their own is known as diffusion.
Fig. Sugar solution when stirred dissolves in water
The above experiment proves that matter is made up particles that are tiny and have spaces between them
EXPERIMENT II:
- Take a beaker filled with water.
- Pour some seeds of pulses and leave the beaker undisturbed.
- Soon you will find that the seeds keeps on moving on the surface of water in a zigzag motion.
- This motion is known as Brownian motion.
- This experiment proves that particles of matter are continuously moving due to which the seeds left undisturbed kept on moving on the surface of water. This means that they possess kinetic energy which rises on rise in temperature because as the temperature rises particles starts to move faster.
Fig. Seeds undergoing brownian motion
The above experiment proves that the particles of matter are continously moving.
EXPERIMENT III:
- We can easily move our hands in a bucket filled with water but if we try to do the same with a solid object it seems impossible because they have greater force of attraction between them that keeps the particles united and hence we cannot separate the particles.
This experiment proves that the particles of matter have force of attraction between them.
States of matter
Matter can be categorised into three states.
Solid state
- They have definite shape due to strong Intermolecular forces of attraction.
- They have distinct boundaries.
- They have a fixed volume.
- They cannot flow.
- They have negligible compressibility due to negligible distance between the neighbouring molecules.
- They possess a tendency to uphold their shape when exposed to external force.
- They break under force but it is difficult to change their shape so they are rigid.
- They have high density and do not diffuse at all.
Fig. Particles of solid (Wooden table) are compact together and have less space between them
Liquid state
A liquid has no definite shape and takes up the shape of the container in which it is kept.
A liquid has a definite volume due to weaker intermolecular force of attraction than solids.
They can flow from a higher lever to a lower level.
A liquid is compressible due to larger distance between the neighbouring molecules than solid but lesser than gas.
They have lower density.
A liquid can diffuse into another liquid due to fact that molecules move faster in a liquid but is slower as compared to gases
Fig. Particles of liquid (water) are loosely packed than solid and have space between them….
Gaseous state
- They do not have definite shape and take up the shape of the container.
- They do not possess definite volume due to weakest intermolecular forces.
- They are not rigid.
- They are easily compressible due to excess space between the particles of gas which compresses on applying pressure.
- They can easily undergo diffusion due to the fact that molecules in a gas moves at a very fast rate due to which speed of diffusion is very large.
- They can flow in all possible directions.
Fig. Particles of gas are loosely packed and have excess space between the particles
Change of state of matter due to effect of temperature
We are already aware of the fact that kinetic energy of the particles of a matter increases with the increase in temperature. Due to this increase in kinetic energy the particles start to vibrate with greater speed. The energy provided by the application of heat breaks the force of attraction between the particles and as a result the particles leave their respective position and starts moving freely.
A phase is reached where at certain temperature solid gets converted to liquid. This temperature at which a solid melts and converts into liquid at atmospheric pressure is termed as melting point.
Fig. Melting of ice on application of heat
Particles of water possess greater kinetic energy at 0oC. On application of more heat the particles of water starts moving faster. At specific temperature the particles acquire enough energy to break free from the forces of attraction of each other. At this temperature the liquid starts changing into gas. This temperature at which a liquid starts boiling and starts converting to gas at the atmospheric pressure is called boiling point.
Fig. boiling of water
Latent heat of fusion
During the melting of solid, the temperature remains the same. The heat gets used up in overcoming the forces of attraction between the particles of matter. The heat energy is being absorbed by solid ice without any rise in temperature. This heat is regarded to be hidden in the contents of the container and is called latent heat.
Fig. Heating of ice to convert it into liquid
It can be further defined as follows:
The amount of energy needed for the conversion of 1kg of solid to liquid at atmospheric pressure at its melting point is known as the latent heat of fusion.
Latent heat of vaporisation
The term latent heat of vaporisation can be defined as the amount of heat needed for the conversion of 1kg of liquid at its boiling point to gas at same temperature. It differs among different liquids.
Fig. Heating of the liquid to convert it into vapour
Particles of water vapour at 100oC (373K) have more energy than liquid water at same temperature. this due to the absorption of extra energy in the form of latent heat of vaporisation.
Change of state of matter due to effect of pressure
Pressure creates no effect on solids or liquids because both these states of matter are non-compressible. But if pressure is increased on solid it breaks.
But on the other hand application of pressure with reduced temperature can liquefy gases. For instance, during parties or stage shows you must have noticed smoke that spreads al around the stage. It is nothing but dry ice (solid carbon-dioxide). Solid carbon-dioxide is stored under high pressure that liquefies instantly as soon as the pressure is reduced to 1 atmospheric pressure.
Fig. Application of pressure can convert gas to liquid which in turn can convert the liquid to solid due to compression of particles.
Processes involved in change of state of matter
Fusion
The phenomenon of change of solid into liquid is termed as fusion. For instance, melting of ice.
Fig. Conversion of solid (ice) to liquid (water)
Solidification
The phenomenon of change of liquid to solid is called solidification. For instance, formation of ice from water.
Fig. Conversion of liquid (water) to solid (ice) by cooling
Condensation
The phenomenon of change of gas to liquid is called condensation. For instance, presence of water droplets on surface of glass containing cold water because the water vapour present in air when comes in contact with the cold glass of water it loses its energy and condenses to liquid state. This is seen as water droplets on the surface of glass.
Fig. Water droplets on the surface of glass containing cold water
You all must have drawn such funny on the windows of your school buses while going to school. This follows the same phenomenon as in case of cold glass.
Sublimation
The phenomenon of change of solid directly to gas or conversion of gas directly to liquid without changing into liquid state is called sublimation. For instance, camphor also called capoor when kept for a long time vanishes. This is due to the sublimation of camphor.
Fig. conversion of solid (camphor) directly into gas without changing into liquid
Evaporation
The three states of matter possess different rate of kinetic energy at different temperature. Due to increase in temperature the particles at the surface of liquid possessing higher kinetic energy are capable to break away from the forces of attraction of other particles present in the surrounding and vaporises. This process of conversion of liquid to vapour at any temperature below its boiling point is termed as evaporation.
For instance, the wet clothes laid outside in the sunlight becomes dry after some time due to the evaporation of water particles form the surface of the clothes.
Factors affecting evaporation
- We are well aware of the fact that evaporation is a surface phenomenon. Therefore increasing the surface area increases the rate of evaporation.
- Increasing temperature also increases the rate of evaporation because with the rise in temperature more number of particles get enough kinetic energy to convert into vapour state.
- Content of water vapour in the atmosphere is known as humidity. It is a well known fact that air can hold water upto a certain amount. If the amount of water in atmosphere is already high then rate of evaporation will decrease. Therefore decreasing the humidity also increases the rate of evaporation.
- It is commonly observed that clothes dry at a fast rate during windy days. This is because with the increase in wind speed the ater particles move away with the windwhich in turn decreases the amount of water vapour from the atmosphere. Therefore increasing the wind speed increases the rate of evaporation.
Evaporation causing coolness
The phenomenon of evaporation takes place in the presence of heat. During this phenomenon the liquid absorbs the heat energy from the surrounding to recover the energy gone astray during evaporation. This absorption of heat energy from the surrounding makes the surrounding area cool.
Due to this fact when you pour acetone on your palm you feel cool because the acetone evaporates by absorbing the heat energy from your palm leaving your palm feel cool.
Fig. Acetone used to remove nail paint makes you feel cool when dropped on skin
Wearing cotton clothes in summer
During summer days we sweat more than usual which keeps us cool. Because the sweat evaporates by obtaining heat from our body and changes into vapour. The heat equivalent to latent heat of vaporaisation is being absorbed from the body that makes he body cool.
It is recommended to wear cotton clothes in summer due to the fact that cotton is good absorber of water that helps to absorb the sweat and brings it in contact to the surrounding atmosphere for easy evaporation.
Fig. Phenomenon of easy evaporation due to cotton cloth
Teenager Helper 