Matter In Our Surroundings | Class 9

Matter

Anything that occupy space (i.e have volume) and have mass is called matter.

Classification of Matter

Matter is classified into groups according to their physical and chemical properties.

e.g. based on physical properties as solid, liquid and gas.

       based on chemical properties as elements, compounds and mixtures.

Diffusion

Diffusion is the process in which molecules of a substance move from higher concentration to lower concentration and goes on until a uniform mixture is formed.

Osmosis

In osmosis, the solvent molecule move from their higher concentration to lower concentration through semi-permeable membrane.

Solid	Liquid	Gas
Solid have definite shape and fixed volume.	Liquids do not have definite shape, i.e. they take the shape of the container in which they are kept but have definite volume.	Gases have neither definite shape nor definite volume.
Solids are rigid they may break under force, but it is difficult to change their shape.	Liquids flow and change the shape, so they are not rigid, but can be called fluid.	Gases also have a tendency to flow. Therefore, they are also considered as fluids.
Solids do not diffuse.	The gases from the atmosphere diffuse and dissolve in water. The rate of diffusion of liquids is higher than that of solids. This is because the particle in liquid moves freely and have greater space in between as compared to solids.	Gases show the property of diffusing very fast into other gases/liquids due to high speed of particles and large space between them.
Negligible compressibility	Liquids are almost incompressible.	Gases are highly compressible. e.g. LPG, CNG, etc.
The attraction force between the particles of solids is maximum as compared to liquid and gases state.	The attraction force between the particles of liquid is greater than that of gases, but less than that of solids.	The force of attraction between the particles of gases is minimum as compared to solid and liquid
Solids have higher densities as compared to their liquid or gaseous forms.	The density of liquid is generally less than that of its solid form.	The density of gases is minimum. A gas is much lighter than the same volume of a solid or a liquid.
The particles of solids have minimum intermolecular space in between them.	The particles of liquid have intermolecular space in between them.	The particles of gases have maximum intermolecular space in between them.

• Facts:-
• A rubber band, changes the shape under the force and regains the same shape when the force is    removed.
• Sugar and salt also take the shape of the container in which they are kept but they are considered as solids.
• Sponge is compressible, but considered as a solid. This is because a sponge has holes, in which air is trapped. when it pressed, the air expelled out and we are able to compress it.
• Density = Mass / Volume.
• The aquatic animals can breath under water due to the presence of dissolved oxygen in water.
• The density of solid form of water (ice) is less as compared to that of the liquid form of water.
• The smell of hot cooked food reaches us in seconds. The particle of the aroma of food mix with the particle of air, reaches us and even farther away.
• The fragrance of perfumes spreads all around due to the diffusion of its particle in air.
• In gaseous state, the particle move about randomly at high speed. Due to this random movement, gas exert pressure on the wall of the container, in which they are kept. 
• Pressure = Force / Area.

Terms involved in change of state

Fusion or Melting and Melting Point

The process of conversion of solid state to its liquid state at specific condition of temperature and pressure, is called Fusion / Melting.

The temperature at which solid starts melting is called its Melting Point.

Boiling and Boiling Point

The process of conversion of liquid state to its vapours (gaseous state) at specific temperature and pressure is called Boiling. It is a bulk phenomenon.

The temperature at which liquid starts boiling is called its boiling point.

Sublimation

The process of conversion of solid state directly into gaseous state without passing through the liquid state is known as Sublimation.

e.g. camphor, naphthalene, ammonium chloride, iodine, etc

Vapourisation

The process of conversion liquid state to its gaseous state at specific condition of temperature and pressure is called Vapourisation.

Freezing and Freezing Point

The process of conversion of liquid state to its solid state at specific condition of temperature and pressure is called Freezing.

The temperature at which liquid change to solid state by giving out heat energy at 1atm is called Freezing Point.

Condensation

The process of conversion of gaseous state to liquid state at specific condition of temperature and pressure is called Condensation.

Latent Heat

The heat energy which has to be supplied to change the state of substance is called its Latent Heat. Latent means Hidden. Latent heat does not raise the temperature, but latent heat is always supplied to change the state of a substance. Latent heat is of two types:

Latent Heat of Fusion (Solid to Liquid)

The amount of heat energy that is required to change 1Kg of a solid into liquid (at atmospheric pressure) at its melting point is known as the Latent Heat of Fusion.

e.g. particle in water at 273.16 K have more energy as compared to particle in ice at the same temperature. 

Latent Heat of Vapourisation (Liquid to Gas)

The amount of heat energy that is required to convert 1 Kg of a liquid into gas (at its boiling point) without any rise in temperature is known as the Latent Heat of Vapourisation.

e.g. particle in steam i.e. water vapour at 373 K have more energy than water at the same temperature.

Note: It has been found that burns caused by the steam are much more severe than those caused by boiling water at same temperature of 373 K.

Evaporation

The process of conversion of a liquid into its vapour state at any temperature below its boiling point is called Evaporation.

Factor Affecting Evaporation.

The rate of evaporation of a liquid depends upon the following factors:

1. Surface Area The rate of evaporation increases on increasing the surface area of the liquid.
2. Temperature The rate of evaporation increases with rise in temperature. With increase of temperature, more number of particles get enough kinetic energy to go into vapour state.
3. Humidity It is the amount of water vapour present in air. If the amount of water in air is already high, the rate of evaporation decreases.
4. Wind Speed With increase in wind speed, the particle of water vapour move away with the wind, decreasing the amount of water vapour in surrounding. That is why, the rate of evaporation increases with increase in wind speed.

Evaporation cause Cooling Effect

1. In an open vessel, the liquid keeps on evaporating. The particle of liquid absorb energy from the surrounding to regain energy lost during evaporation. This absorption of energy from the surrounding makes the surrounding cold.
2. When ice cold water is kept in a glass tumbler for sometime, water droplets are observed on its outer surface. This occurs as the water vapour present in the air comes in contact of the glass tumbler, get cooled and condensed to form these small water droplets.
3. Cotton clothes are used to wear during summer. Cotton is good absorber of water, so it helps to absorb sweat from our body. when this sweat evaporates, it takes the latent heat of vapourisation from our body, which in turn, cool our body.
4. People sprinkle water on the roof or open ground on a hot sunny day. When water is sprinkled on a hot surface, it get evaporated very quickly. As evaporated water leaves the surface cool due to the large latent heat of vapourisation of water.
5. Liquid like acetone (nail-polish remover) or alcohol placed on your palm give you feeling of cooling. Acetone and alcohols are volatile liquids. When kept on palm, their particle gain energy from the palm or surroundings and evaporate causing the palm to fell cool.
6. Using desert cooler to get relief during summer. During summer, humidity is less and temperature is high, so the rate of evaporation is fast. Thus water present inside the desert cooler evaporates more, thereby cooling the surroundings more.
7. Keep water in earthen pots to keep it cool. Earthen pot has a large number of tiny pores in its walls and some of the water molecules continuously keep seeping through these pores to outside the pot. This water evaporates continuously and takes the latent heat required for vaporization from the remaining water. In this way, the remaining water loses heat and gets cooled.
   

Application of Evaporation in daily life

1. Drying of clothes after washing.
2. Using desert cooler to get relief during summer.
3. Keep water in earthen pots to keep it cool.
4. Wearing of cotton clothes in summers as they easily absorb sweat and help in its easy evaporation. 

Difference between Boiling and Evaporation

Boiling	Evaporation
Boiling occurs at a particular temperature i.e. Boiling point of that liquid.	Evaporation takes place when liquid is placed in open container at any temperature below it boiling point.
Boiling is bulk phenomenon	Evaporation is a surface phenomenon.
Heating take place during boiling	Cooling take place during evaporation
For boiling heat from an external source required.	For evaporation liquid absorb heat from the surrounding.