Class IX

Matter in our surroundings – Class IX – In-text Solution (Part 4)

(Answers of In-text Question in NCERT Science Text Page 10)

1. Why does a desert cooler cool better on a hot dry day?

Ans: Desert cooler works on the principle of cooling effect of evaporation. In hot and dry days the moisture level is very low in atmosphere & the temperature is high hence it increases the rate of evaporation. Because of faster evaporation, cooler works better.

2. How does the water kept in an earthen pot (matka) become cool during summer?

Ans: 

  • In summer moisture level is very low in the atmosphere & the temperature is also high, which therefore increases the rate of evaporation.
  • Water from porous wall of earthen pot thus evaporates continuously, which lowers the temperature of water kept in the earthen pot due to the cooling effect of evapouration.
  • That is why in summer, water kept in earthen pot becomes cool.

3. Why does our palm feel cold when we put some acetone or petrol or perfume on it?

Ans: When acetone(used in nail-polish remover)/petrol/perfume is poured over palm, it evaporates quickly as these are volatile liquids. The evaporation lowers the temperature of palm and our palm feels cold.

4. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?

Ans: When hot tea or milk is kept in a saucer, the liquid is exposed over a larger surface area as compared to in case of the liquid being kept in a cup. The larger surface area increases the rate of evaporation, thus enables faster cooling. That’s why we are able to sip hot tea or milk faster from a saucer rather than from a cup.

5. What type of clothes should we wear in summer?

Ans: We should wear cotton cloths in summer. As cotton cloths are good absorbent of sweat excreted in summer and also because they enable the sweat to evaporate. Because of evaporation of sweat from the surface of cotton cloth, we feel colder and comfortable.

Matter in our surroundings – Class IX – In-text Solution (Part 3)

(Answers of In-text Question in NCERT Science Text Page 9)

1. Convert the following temperature to Celsius scale.

(Temperature on Celsius scale = Temperature of Kelvin scale – 273)

(a) 300 K

Ans : 300 Kelvin (K) – 273 = Temperature in Celsius = 27⁰C

(b) 573 K

Ans : 573 Kelvin (K) – 273 = Temperature in Celsius = 300⁰C

2. What is the physical state of water at

(a) 250⁰C

Ans: Water boils at 100⁰C and therefore the physical state of water at 250⁰C is gaseous (water vapour).

(b)100⁰C

Ans: Since, the water boils at 100⁰C, thus at 100⁰C water is in transition phase, therefore the water at 100⁰C is in both liquid and gaseous state.

3. For any substance why does the temperature remain constant during the change of state.

Ans:  During the change of state of any substance, the heat supplied or released is utilised in the phase change. Such heat is called latent heat. So, the temperature of any substance remains constant during the change of state.

4. Suggest a method to liquefy atmospheric gas.

Ans: Atmospheric gas can be liquefied by increasing pressure and decreasing temperature.

Matter in our surroundings – Class IX – In-text Solution (Part 2)

(Answers of In-text Question in NCERT Science Text Page 6)

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.

Ans :

  • Air is the mixture of gases and it is the least dense among the given matters.
  • Chimney exhaust is also a mixture of gases; along with some heavier particles, such as ash. This makes the density of chimney exhaust more than air.
  • Cotton is a porous solid and which has lot of air trapped within pores. This makes its volume more than water. Therefore, it is less dense than water.
  • Honey is also a liquid; along with some dense particles, hence it is more denser than water.
  • Chalk is a solid and as compared to honey is more denser while it is less denser as compared to the Iron.
  • Iron is the densest among the given matters.

Air < Exhaust from chimneys < Cotton < Water < Honey < Chalk < Iron

2. (a) – Tabulate the differences in the characteristics of states of matter.

Ans:

2. (b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density

Ans:

  • Rigidity: The greatest force of attraction between particles and close packing of particles make solids rigid. Rigidity is one of the unique properties of solids. Because of rigidity a solid has definite shape and volume. Rigidity is negligible in fluid and gas.
  • Compressibility: Compressibility is one of the most important characteristics of gas. Because of lot of space between particles, a gas can be compressed to a great extent. Liquid and solid cannot be compressed because of the least space between their particles.
  • Fluidity: The ability to flow is called fluidity. The less force of attraction and more space between particles make liquid and gas to flow. That’s why liquid and gas are called fluid.
  • Filling of a gas container: Liquids do not fill a gas container completely, while gases fill the gas container completely in which it is kept. This is because the particles of gas can move in all the directions.
  • Shape: Solids have fixed shape. Liquid and gas take the shape of the container in which they are kept. This happens because of less force of attraction and more kinetic energy between particles of liquids and negligible force of attraction and highest kinetic energy between particles of gas.
  • Kinetic energy: The kinetic energy of particles of solid is the minimum. They only vibrate at their fixed position. The kinetic energy of particles of liquid is more than that of solid. But they can slide above one another. The kinetic energy of particles of gas is the maximum.
  • Density: The mass per unit volume of a substance is called density. The density of solid is highest, of liquid is less than solid and of gas is minimum.

3. Give Reasons

(a) A gas fills completely the vessel in which it is kept.

Ans: The force of attraction between particles of gas is negligible, therefore particles of gas move in all directions. Thus, a gas fills the vessel completely in which it is kept.

(b) A gas exerts pressure on the walls of the container.

Ans: As there is only negligible force of attraction between particles of gas, they have the highest kinetic energy. These properties enable the particles of gas to move in all directions and hit the walls of container from all sides. Because of this a gas exerts pressure on the walls of the container in which it is kept.

(c) A wooden table should be called a solid

Ans: A wooden table is should be called a solid because it has definite shape and definite volume, which are the main characteristics of 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.

Ans:

  •  As Air is gas, its particles are loosely packed and there is negligible force of attraction between its particles. Because of that we can easily move our hand in air.
  • But wood is a solid, so the force of attraction between its particles is greatest. The particles of wooden block are closely packed. That’s why we cannot move our hand through a solid block of wood.
  • However a karate expert can exert required pressure to break the great force of attraction of the particles of a solid wooden block.

4. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.

Ans: During freezing of water, some space between the particles of water is left vacant with some air trapped between them. These empty spaces having air in them, makes the density of ice lower than that of water. That’s why ice floats on water.

Matter in our surroundings – Class IX – In-text Solution (Part 1)

(Answers of In-text Question in NCERT Science Text Page 3)

1. Which of the following are matter ? – Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.

Ans : Chair, Air, Almonds, Cold-drink are matters as they occupy space & have mass.

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.

Ans:

  • Smell of anything  reaches to us because of diffusion of gases coming from it.
  • The rate of diffusion increases with increase in temperature. This happens because of higher kinetic energy due to higher temperature. That is why smell of hot sizzling food reaches to us from several feet away.
  • On the other hand, the kinetic energy of gases produced from cold food is low because of lower temperature. Due to this, we need to move closer to a cold food to take its smell.

3. A diver is able to cut through water in a swimming pool. Which property of mater does this observation show?

Ans:

  • Water is also a matter.
  • Particles of matter have space between them and in case of fluids, the space between the particles is large enough.
  • Due to this it becomes easier for a diver to cut through water in a swimming pool.

4. What are the characteristics of the particles of matter?

Ans: Characteristics of the particles of matter:

  • The particles of matter have space between them.
  • The particles of matter are moving constantly.
  • The particles of matter attract one another.

Adult Education – (Class IX English)

Personal View

adult-educationI personally believe adult education is very important.  Some people in their early age did not get chance for learning, but if they get opportunity to get educated they can fulfil their dream to study and can discover their life in a new way. Adult education makes them more up-to-date and self-reliant. Many illiterate adults often think themselves as incapable of learning at their age, but education has no age bar. Educating the adults not only helps them to be independed but also helps them to differentiate between what is good and what is bad.

In olden times people did not send their girl child to school, the young girls were made to work in the home and were married very early. Sending the girls to school, the people believed will make her a “widow”. But after several reforms in the British period for “women education”, the uneducated woman’s started sending their girl child to school. But the learning dream of those uneducated women’s stays unfulfilled. They can get a chance for fulfilling their dreams of learning through the process of adult education.

During the British period, children of many poor peasants didn’t get a chance to learn, as they had to help their parents in the work. At Independence (in 1947), India’s literacy rates were 12.2% and today according to the 2011 census the literacy rates has risen high to 74%.  This clearly shows that India’s literacy rates are growing constantly, but still a large percent of adults are illiterate.  In a complex modern democracy like India, citizens must be educated, they should know about the things happening around, like corruption & terror. So in order to educate the adults, adult education, I believe is necessity.

Websites Referred:

Negative Aspects of Adult Education

  • The problems faced by the adults in education are the only major negative aspect of Adult Education, which include :-
  1. Advancements in technologies cannot be used effectively by adult learners easily.
  2. Emotional & Physical problems will be more for an Adult learner when studying.
  3. Academic Calenders & routines are often incompatible with their work schedules.
  4. Life situations can be obstacles in the performance of adult learners.

Positive Aspects of Adult Education

  • Some adults spend much of their time to take rest, but if they are engaged in learning,  they not only get educated but also can have fun & friends.
  • Research shows that older people who keep their brain active suffer less memory-type diseases, so education helps them as their brain is actively used.
  • If the adults are busy in some creative jobs i.e. learning, they will never feel boring rather they will feel happy & healthy.

Steps of measures taken by the government to promote Adult Education

  • The Department of  School Education & Literacy under the Ministry for Human Resource Development has introduced several policies & programmes  for the promotion of adult education .
  • National Literacy Mission (NLM), that was launched in 1988 to impart functional literacy to non-literates in the age group of 15-35 years in a time bound manner.  It had made 127.45 million persons literate,  It led to an increase of 12.63% in literacy during 1991-2001 – the highest increase in any decade.
  • Government of India, has been providing support to Voluntary Agencies (VA),  which encourages innovation and creativity in literacy and continuing education. It includes establishment of State Resource Centres for technical and academic support to adult education.
  • Jan Shikshan Sansthans, on the other hand, provide vocational education skill development training to those having no or rudimentary level of education.

Websites Referred: http://mhrd.gov.in/ 

Complete Speech

In a complex modern democracy like India, education is essential, citizens must be able to know about the things happening around, and moreover should be able to differentiate between what is good and what is bad.  Unfortunately,  our nation has the largest number of illiterate adults, about 287 million adults in India are illiterate. Therefore, the need of adult education in India is clearly a critical problem.

Education makes adults more up-to-date and self-reliant, and therefore opens a new world of freedom to them.  By involving in learning activities, adults will never feel boring  rather they will feel more healthy & happy. Education has no age bar and no limits, so even the oldest person can learn anything, if he wishes. For promoting adult education in India, the government has introduced several programmes, which has resulted in the increase of adult literacy from 12% in 1947 to 74% in 2011.  Therefore, I conclude my speech by a saying a quote – “Education is the key to unlock the golden door of freedom.”