Topic:- Introduction
Definition:-Anything that occupy space and have mass is called matter.
Early Indian philosopher classified matter in the form of five basic elements- Panch tatva - earth, sky, air, fire and water.
Modern day scientists have evolved two types of classification of matter based on their physical and chemical nature.
In this chapter we shall learn about matter based on its physical properties.
Physical Nature of Matter
Matter is made up of particles.
Size of particles is beyond our imagination.
Characteristics of Particles of Matter.
*Particles of matter have space between them.
*Particles of matter are continuously moving.
*Particles of matter attract each other
Diffusion:-Movement of particles from higher concentration region to lower concentration region.
Rate of diffusion is higher in gases.
States of Matter
three states.
1 solid
2 liquid
3 gas
SOLID STATE:-
*Fixed shape
*Fixed volume
*Distinct boundary
*Strong force of attraction between particles,
*very small intermolecular distance
*Rigid
*negligible compressibility
*Don't flow
*show diffusion
*rubber band have special property of elasticity .
*sponge have minute holes through which air expell out when compress.
#LIQUID STATE:-
*NO Fixed shape
*Fixed volume
*NO Distinct boundary
*week force of attraction between particle
*have intermolecular distance
*Non-Rigid
* compressibility
* flow
*show diffusion
GASES:-
*No Fixed shape
*No Fixed volume
*No boundary
*weakest force of attraction between particles,
*very large intermolecular distance
*non- Rigid
*highly compressible
*flow
*show diffusion
Can Matter Change it's state?
Yes
Factors which can change the state of matter:-
1. Effect of change of temperature
2. Effect of change of pressure.
Effect of Change Of Temperature:-
On increasing the temperature of solids, the kinetic energy of particles increases.
Due to increase in kinetic energy, the particles start vibrating with greater speed.
The energy supplied by heat overcomes the forces of attraction between the particles.
The particles leave their fixed position and start moving more freely.
A stage is reached when the solid melts and is converted into liquid.
Melting point:- The minimum temperature at which solid melts to become a liquid at the atmospheric pressure is called melting point.
mp of water(ice) is 0°C.
Melting point of a solid indicate the strength of forces of attraction between its particles.
Latent heat of fusion:- Amount of heat energy required to convert 1 kg of solid into liquid at atmospheric pressure at its melting point is known as latent heat of fusion.
Boiling point:- The temperature at which a liquid starts boiling at the atmospheric pressure is known as it's boiling point.
Boiling is a bulk phenomenon.
Particles from the bulk of the liquid gain enough energy to change into the vapour state.
Sublimation:- the process of change of solid into gas without changing into liquid is called sublimation and direct change of gas to solid without changing into liquid is called deposition.
Examples that show sublimation are:- camphor, ammonium chloride, dry ice (solid CO2)
Note:- Particles of liquid have more energy than particles of solid at its mp . Due to absoption of latent heat of fusion.
So at 273k (0°C) ice is more effective in cooling than water at the same temperature.
Particles of gas have more energy than particles of liquid at its bp . Due to abosption of latent heat of vaporisation.
Effect of change of pressure in state change:-
On increasing the pressure, the interparticular distance increases.
That's why we can convert gases to liquid and liquid to solid by increasing the pressure.
Solid CO2 gets converted directly to gaseous state on decrease of pressure to 1 atmosphere without changing into liquid state. This is the reason that solid CO2 is called dry ice
Evaporation:
The phenomenon of change of a liquid into vapours at any temperature below its boiling point is called evaporation.
#Factors affecting evaporation:-
1.Surface area{ larger the surface area larger will be rate of evaporation.}
2.Temperature{higher the temp higher will be rate of evaporation.}
3.Humidity{Higher the humidity, lesser will be the rate of evaporation.}
4.Wind Speed{Higher the wind speed ,faster will be the rate of evaporation.}
#How does evaporation cause cooling?
-By absorbing heat .
*Desert cooler cool better on a hot dry days because air drops coming out of it absorb heat from surrounding and evaporate and evaporation cause cooling.
*Water kept in an earthen pot become cool during summer because heat transfer from inside water to surface water and this surface water gets evaporate through air pores present in earthen pot. due to evaporation water become cool
* When we put some acetone or petrol or perfume in our palm ,we feel cool because it's substances absorb heat from our palm nd gets evaporate . and evaporation cause cooling.
* We are able to sip hot tea or milk faster from a saucer rather than a cup because by increasing surface area rate of evaporation increases and evaporation cause cooling.
* Cotton cloth should be wear in summer because it absorb moisture and thus water drop come to surface and gets evaporate.thus evaporation cause cooling.
*When ice cold water is pour in tumbler ,water droplets see on outside surface of tumbler because water vapour present in air ,on coming in contact with cold glass of water, loses energy and converted into liquid state.
how to convert °C into K
°C = 273 + K
300k =____°C
573k =____°C
25°C =____°C
373°C = __°C
Ques ans:-
Page no:- 3
Question 1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.
Answer: Chair, air, almonds, and cold-drink.
Question 2. Give reasons for the following observation:
The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.
Answer: The smell of hot sizzling food reaches severed meters away, as the particles of hot food have more kinetic energy and hence the rate of diffusion is more than the particles of cold food.
Question 3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Answer: A diver is able to cut through water in a swimming pool. This shows that the particles of water have intermolecular space and has less force of attraction
Question 4. What are the characteristics of the particles of matter?
Answer. The characteristics of the particles of matter are:
(1) Particles have intermolecular space.
(2) Particles have intermolecular force.
(3) Particles of matter are moving continuously.
Page no. 6
Question 1. The mass per unit volume of a substance is called density.
(density = mass/volume).
Arrange the following in order of increasing density: air, exhaust from chimneys, honey, water, chalk, cotton and iron.
Answer: Increasing density:
air < exhaust from chimneys < cotton < water < honey < chalk < iron.
Question 2. (a) Tabulate the differences in the characteristics of states of matter.
(b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
Answer: (a) Difference in the characteristics of 3 states of matter.
b) Comment on:
(i) Rigidity: The tendency of a substance to retain/maintain their shape when subjected to outside force.
(ii) Compressibility: The matter has intermolecular space. The external force applied on the matter can bring these particles closer. This property is called compressibility. Gases and liquids are compressible.
(iii) Fluidity: The tendency of particles to flow is called fluidity. Liquids and gases flow.
(iv) Filling of a gas container: Gases have particles which vibrate randomly in all the directions. The gas can fill the container.
(v) Shape: Solids have maximum intermolecular force and definite shape.
Whereas liquids and gases takes the shape of container.
(vi) Kinetic energy: The energy possessed by particles due to their motion is called kinetic energy. Molecules of gases vibrate randomly as they have maximum kinetic energy.
(vii) Density: It is defined as mass per unit volume, the solids have highest density.
Question 3. Give reasons
(a) A gas fills completely the vessel in which it is kept.
(b) A gas exerts pressure on the walls of the container.
(c) A wooden table should be called a solid.
(d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.
Answer: (a) The molecules of gas have high kinetic energy due to which they keep moving in all directions and hence fill the vessel completely in which they are kept.
(b) A gas exerts pressure on the walls of the container because the molecules of the gas are in constant random motion due to high kinetic energy. These molecules constantly vibrate, move and hit the walls of the container thereby exerting pressure on it.
(c) The molecules/particles of wooden table are tightly packed with each
other, there is no intermolecular space, it cannot be compressed, it cannot flow, all these characteristics are of solid. So wooden table should be called a solid. ‘
(d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert. It is because the molecules of air has less force of attraction between them and a very small external force can separate them and pass through it. But in case of solids, the molecules have maximum force of attraction, the particles are tightly bound due to this force. Hence large amount of external force is required to pass through solid.
Question 4. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Answer: Ice is a solid but its density is lower than water due to its structure. The molecules in ice make a cage like structure with lot of vacant spaces, this makes ice float on water.
Page no. 9
Question 1. Convert the following temperature to Celsius scale:
(a) 300 K (b) 573 K
Answer. (a) 300 – 273 = 27°C (b) 573 – 273 = 300°C
Question.2. What is the physical state of water at:
(a) 250°C (b) 100°C
Answer: (a) 250°C = gas (b) 100°C liquid as well as gas
Question 3. For any substance, why does the temperature remain constant during the change of state?
Answer: During the change of state of any matter heat is supplied to the substance. The molecules of this matter use heat to overcome the force of attraction between the particles, at this period of time, temperature remains constant. This extra heat is acquired by the molecules in the form of hidden heat called latent heat to change from one state of matter to the other state.
Question 4. Suggest a method to liquefy atmospheric gases?
Answer: By increasing pressure and decreasing temperature we can liquefy atmospheric gases.
Page no. 10
Question 1. Why does a desert cooler cool better on a hot dry day?
Answer: The outer walls of the cooler get sprinkled by water constantly. This water evaporates due to hot dry weather. Evaporation causes cooling of inside air of cooler. This cool air is sent in the room by the fan.
Question 2. How does the water kept in an earthen pot (matka) become cool during summer?
Answer: The earthen pot is porous with lot of pores on it, the water oozes out through these pores and the water gets evaporated at the surface of the pot thereby causing cooling effect.This makes the pot cold and the water inside the pot cools by this process.
Question 3. Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Answer: Acetone, petrol or perfume evaporate when they come into contact with air. The evaporation causes cooling sensation in our hands.
Question 4. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Answer: Tea in a saucer has larger surface area than in a cup. The rate of evaporation is faster with increased surface area. The cooling of tea in saucer takes place sooner than in a cup. Hence we are able to sip hot tea or milk faster from a saucer rather than a cup.
Question 5. What type of clothes should we wear in summer?
Answer: We should wear light coloured cotton clothes in summer. Light colour because it reflects heat. Cotton clothes because it has pores in it, which absorbs sweat and allows the sweat to evaporate faster thereby giving cooling effect
Page no 12
Question 1. Convert the following temperatures to the Celsius scale.
(a) 293 K (b) 470 K.
Answer: (a) 293 K into °C
293 – 273 = 20°C
(b) 470 K into °C 470 – 273 = 197°C
Question 2. Convert the following temperatures to the Kelvin scale.
(a) 25°C (b) 373°C.
Answer: (a) 25°C into K
25 + 273 = 298 K
(b) 373°C into K 4 373 + 273 = 646 K
Question 3. Give reason for the following observations.
(a) Naphthalene balls disappear with time without leaving any solid
(b) We can get the smell of perfume sitting several metres away.
Answer: (a) Naphthalene balls disappear with time without leaving any solid, because naphthalene balls sublime and directly changes into vapour state without leaving any solid
b) We can get the smell of perfume sitting several metres away because perfume contain volatile solvent and diffuse faster and can reach people sitting several metres away.
Question 4. Arrange the following substances in increasing order of forces of attraction between the particles—water, sugar, oxygen.
Answer: Oxygen —> water —> sugar.
Question 5. What is the physical state of water at—
(a) 25°C (b) 0°C (c)100°C
Answer: (a) 25°C is liquid (b) 0°C is solid or liquid
(c) 100°C is liquid and gas
Question 6. Give two reasons to justify
(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.
Answer: (a) Water at room temperature is a liquid because its freezing point is 0°C and boiling point is 100°C.
(b) An iron almirah is a solid at room temperature because melting point of iron is higher than room temperature.
Question 7. Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer: Ice at 273 K will absorb heat energy or latent heat from the medium to overcome the fusion to become water. Hence the cooling effect of ice is more than the water at same temperature because water does not absorb this extra heat from the medium.
Question 8. What produces more severe bums, boiling water or steam?
Answer: Steam at 100°C will produce more severe bums as extra heat is hidden in it called latent heat whereas the boiling water does not have this hidden heat.
Question 9. Name A, B, C, D, E and F in the following diagram showing change in its state
Answer: A —> Liquefication/melting/fusion B —> Vapourisation/evaporation C—>Condensation D—> Solidification E —> Sublimation F —> Sublimation
Thankyou :-)
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