SUBJECT : CHEMISTRY
LESSON NO. 1 MATTER IN OUR SOURRNDING
…QUESTIONS AND ANSWERS…
Q 1 : List two ways to liquefy gases. – 1 mark.
Q 2 : Give reasons for the following. – 3 marks.
A] Water droplets appear on the outer surface of the tumbler containing ice cold water.
B] People preferred to wear cotton clothes in summer.
C] On a hot sunny day people sprinkle water on the roof or the open ground.
Q 3 : What is evaporation? List the factors that affect the rate of evaporation and explain their effect on it. – 5 marks.
Q 4 : Write the name of any two substance that
sublime . – 1 mark.
Q 5 : Carbon dioxide is a gas. Write any two properties to justify it. – 2 marks.
Q 6 : How can we liquefy the gas? Solid carbon dioxide is known as dry ice. Why? – 3 marks.
ANS: Carbon dioxide has either fixed volume or fixed shape. It exerts pressure due to collision of the molecules happen. Carbon dioxide can be liquefy by reducing temperature or by increasing pressure .Solid carbon dioxide gets connected directly into gaseous state without coming into liquid state.
Q 7 :Define the following properties of matter.
A] [1–] Rigidity [2 –] Diffusion [3 –]
Compressibility – 3 marks.
B] Arrange solid liquid and gaseous in the ascending order as regards the extent to which each of the above properties is executive them . – 1 mark.
C] Write any one example from your daily life experience which is based on diffusion of gases. – 1 mark.
Q 8 :Define the following : - - 6 marks.
A] -  Rigidity, Fluidity,Density .
B] – For any substance , why does the temperature remains constant during the change of state.
C] – What types of clothes should we wear in summer?
D] – why is the rate of diffusion of gases is faster in gaseous?
Q 9] – Express the following in Kelvin Scale. – 2 marks.
1] – 25 Degree Celsius , 2] – 373 degree Celsius
Q 10] – We can easily move our hands in air. But not through any solid materials. Justify the statement giving any three possible reasons. – 2 marks .
Q 11] – [A] Differentiate between three states of matter on the basis of the following properties :- - 3 marks.
I] Intermolecular forces.
II]Arrangement of molecules.
B] Liquid generally have low density but you must have observed that ice floats on water.
Q 12] [A] – Explain giving one example of each factors , how rate of evaporation of water depends on each of
them. – 2.5 marks.
B] – Explain which one will cause more severe burns: boiling water at 100 degree Celsius or steam. – 2.5 marks.
Q 13] Does a evaporation cause a physical change or a chemical change . – 1 mark.
Q 14] Define the following terms: - 3 marks.
A] Latent heat of fusion.
B] Melting point.
Q 15] [A]Define matter. Name the state of matter in which the forces between the constituent particles are: - 2 marks.
[B] Give reason for the following – 3 marks.
 A liquid generally flows easily.
 Ice at 0 degree Celsius appears colder to the mouth than water at 0 degree Celsius. Why?
 Doctor advice to put strips of wet clothes on the forehead a person having high temperature.
Q 16] List any two properties of particles of matter. – 2 marks.
Q 17] Give reason for the following – 3 marks.
A] Why does ice floats on water.
B] Why does the gas feels compeletely in vessels in which it is kept.
C] Latent heat of evaporation of two liquids A and B 100 joules/kg .150 Joules/Kg respectively. Which one can produce more cooling effect and why?
Q 18] State all the factors that affect the rate of evaporation of water .Discuss how each one of these factors affect the rate of evaporation. – 5 marks.
Q 19] With the help of the diagram describe an activity to show that the state of water can be changed from solid to liquid and then to its gaseous state . Explain the term latent heat of evaporation and latent heat of vaporization. How will you change water from its gaseous state to liquid state suggest a simple activity. – 5 marks.
Q 20] Why does the level of water not changed when common salt is dissolved in water? – 1 mark.
Q 21] [A] What is matter? – 1 mark.
[B] “The rate of diffusion in liquid is higher than that of solids”. Why? – 1 mark.
[C] Write two properties of gases and two properties of
solids. - 2 marks.
[D] Write the full form of : - - 1 mark.
I – LPG.
II – CNG.
Q 22] Define boiling point of liquid. At What temperature in Kelvin scale does water boil. – 5 marks.
Q 23] Explain what will happen when we supply heat energy to water till it changes its state. What is this heat energy
called? – 2 marks
Q 24] The melting point of three solids X , Y and Z are
298 Degree Kelvin , 314 Degree Kelvin , 398 degree Kelvin.
Arrange these in increasing order of their interparticle force of attraction. – 3 marks.
Q 25] Suggest an activity to show that the rate of diffusion of liquids decreases with increase in density of liquids . – 3 marks.
Q 26] Name A , B , C , D , E , and F in the following diagram [page no. 12 of Science Textbook] Showing change in its
state. - 2 marks.
Q 27] Distinguish in tabular form between Solid , Liquid , and Gaseous under the following characteristics : - 5 marks .
1. Intermolecular attraction.
5. Kinetic energy of particles at a given temperature.
Lower than solids
Doesn’t posses [not fluids]
Faster than solids
Higher than solids
Q 28] What is evaporation? In the following examples state which factors is responsible for the change in rate of evaporation and how. – 5 marks
1. Clothes dry faster on windy day.
2. Wet clothes dry faster by spreading them.
3. Clothes dry faster in sun then in days.
4. Clothes take longer time to dry on rainy days.
ANS: Evaporation: The phenomenon of changing of liquid into vapours at any temperature below its boiling point is called evaporation. Factors that are responsible for the change in rate of evaporation are:
1. Wind speed increase , evaporation rate increases.
2. Surface area increases , rate of reaction increases.
3. Temperature increases , rate of evaporation increases.
4. Humidity increases , rate of reaction decreases.
Q 29] In which types of clothes would be you more comfortable in summer. – 1 mark.
Q 30] [A] Define boiling point . – 1 mark.
[B] Express boiling point of water in Celsius as well as Kelvin scale. – 1 mark.
[C] A diver can be able to cut through water in a swimming pool . Which property of matter does the observation
show. – 2 marks.
Q 31][A] What is matter? Write two properties of solid and liquids. – 2 marks
[B] Rakesh took two beakers A and B containing hot water and cold water respectively. In each beaker he drops a crystal of Copper Sulphate. He kept the beaker undisturbed . After sometime what did he observed why? – 2 marks.
Q 32] Define melting point of solid. At what temperature in the Kelvin scale does ice melts ? In the experiment to determine the melting point of ice , why does the temperature not rise even though heat is continuously supplied . What is this heat energy called? - 5 marks
Due to paucity of time it would not be possible for us to provide the answers to all your queries. We are providing solutions to some your good queries. Try solving rest of the questions yourself and if you face any difficulty then do get back to us.
A-1) Gases can be liquefied by
- By applying high pressure. As gases are highly compressible, on applying high pressure, the molecules of a gas would come close, intermolecular forces would increase and it will condense into a liquid.
- By lowering the temperature. Gases can be converted into liquids by simple cooling. At very low temperatures, the gases convert to liquids.
A-3) The process of conversion of a liquid into its vapours at any temperature below its boiling point is known as evaporation. The rate of transformation of a liquid into vapours depends on various factors. They are:
- Humidity - Air can hold only a certain amount of water vapour at a particular temperature. Therefore, if humidity is high, there is no space for more vapour. Hence, the rate of evaporation decreases with increase in humidity.
- Temperature - The rate of evaporation increases with increase in temperature. With an increase in the temperature, kinetic energy of the particles also increases and more and more particles are able to break through the force of attraction from other particles. Hence, they get converted into vapours.
- Wind Speed - The rate of evaporation increases with an increase in the wind speed. This is because fast moving air takes away water vapours from the atmosphere, thereby decreasing its amount, and making room for more. As a result, more evaporation occurs.
- Surface Area - Increase in the surface area increases the rate of evaporation. If the surface area is large, then there will be more molecules on the surface to turn into vapours.
A-4) Camphor, dry ice, naphthalene are the substances which undergo sublimation.