CLASS-9 SCIENCE CHAPTER 1-MATTER – EXEMPLER QUESTION
Short Answer Questions
Question-1- A sample of water under study was found to boil at 102ºCat normal temperature and pressure. Is the water pure? Will this water freeze at 0ºC? Comment.
Answer- The boiling point of pure water is 100ºC. As the boiling point of this sample of water is 102ºC, it is not pure. Due to impurity water will freeze below 0ºC.
Question-2- A student heats a beaker containing ice and water. He measures the temperature of the content of the beaker as a function of time. Which of the following figures would correctly represent the result? Justify your choice.
Answer-Initially ice and water mixture will be at 0ºC. As heat is supplied, the ice will melt at 0º. The temperature will remain 0ºC for the time interval taken for the ice to melt. Now we have only water at 0ºC. On further heating the temperature will start rising. The above characteristics are correctly shown by Fig.(d).
Question-3- Fill in the blanks:
(a) Evaporation of a liquid at room temperature leads to a cooling effect.
(b) At room temperature the forces of attraction between the particles of solid substances are much stronger than those which exist in the gaseous state.
(c) The arrangement of particles is less ordered in the liquid state. However, there is no order in the gaseous state.
(d) sublimation is the change of gaseous state directly to solid state without going through the liquid.
(e) The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called Evaporation.
Question-4- Match the physical quantities given in Column (A) to their SI units given in Column (B):
Column (A) Column (B)
(a) pressure-(iii) (i) cubic meter
(b) temperature-(iv) (ii) kilogram
(c) density-(v) (iii) pascal
(d) mass-(ii) (iv) kelvin
(e) volume-(i) (v) kilogram per cubic meter
Question-5- The non – SI and SI units of some physical quantities are given in Column (A) and Column (B) respectively. Match the units belonging to the same physical quantity:
Column(A) Column(B)
(a) Degree Celsius-(iv) (i) kilogram
(b) Centimeter-(iii) (ii) pascal
(c) Gram per meter-(v) (iii) meter
(d) Bar-(ii) (iv) kelvin
(e) Milligram-(i) (v) kilogram per meter cube
Question-6- ‘Osmosis is a special kind of diffusion’. Comment.
Answer- Diffusion is the spontaneous movement of particles from a region of higher concentration to lower concentration so that the concentration becomes equal in all regions. Osmosis is the spontaneous movement of solvent molecules through a semipermeable membrane from a high solvent concentration region is called osmosis. Therefore, the statement given in the question is correct.
Question-7- Classify the following into osmosis/diffusion.
(a) Swelling up of raisin on keeping in water.
Answer- Osmosis
(b) Spreading of virus on sneezing.
Answer- Diffusion
(c) Earthworm dying on coming in contact with common salt.
Answer- Osmosis
(d) Shrinking of grapes kept in thick sugar syrup.
Answer- Osmosis
(e) Preserving pickles in salt.
Answer- Osmosis
(f) Spreading of smell of cake being baked throughout the house.
Answer- Diffusion
(g) Aquatic animals using oxygen dissolved in water during respiration.
Answer- Diffusion
CLASS-9 SCIENCE CHAPTER 1-MATTER – EXEMPLER QUESTION
Question-8- Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.
Answer- Water in the form of ice is at lower temperature. Our body temperature is greater than the temperature of ice. Therefore, when ice is exposed to our body, heat starts flowing from our body to ice thereby giving cooling effect.
Steam is at a much higher temperature than our body temperature. So, if accidently our body is exposed to steam, heat flows from steam to our body producing severe burns.
Question-9- ALKA was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle . Comment.
Answer- The temperature of boiling water as well as steam is 100ºC. But steam possesses greater heat energy than boiling water because of latent heat of vaporization. Therefore, steam gives more intense heat than boiling water.
Question-10- A glass tumbler containing hot water is kept in the freezer compartment of a refrigerator (temperature<0ºC). If you could measure the temperature of the content of the tumbler, represent the change in its temperature as a function of time.
Answer- Water will start losing heat and its temperature will fall till it reaches ºC. This why is the freezing point of water. Water will still lose heat and convert into ice at 0ºC only. When the complete water has been converted into ice at 0ºC, then the temperature of ice will start decreasing with time. Graph (a) shows this situation correctly.
Question-11- Look at figure given and suggest in suggest in which of the vessels A,B,C or D the rate of evaporation will be the highest? Explain.
Answer- The rate of evaporation increases with (i) increase in surface area and (ii) speed of air. The correct option is therefore (c).
Question-12-(a) Conversion of solid to vapor is called sublimation. Name the term used to denote the conversion of vapor to solid.
Answer- The conversion of vapor to solid is called sublimation.
(b) Conversion of solid state to liquid state is called fusion; what is meant by latent heat of fusion?
Answer- The amount of heat required to convert 1 kg of solid into liquid at one atmosphere pressure as its melting point is called latent heat of fusion.
LONG ANSWER QUESTIONS
Question-13- You are provided with a mixture of naphthalene and ammonium chloride by your teacher. Suggest an activity to separate them with well?
Answer- We dissolve the given mixture of naphthalene and ammonium chloride in water. Ammonium chloride dissolves in water but naphthalene remains insoluble. We filter the above mixture. Naphthalene is obtained as residue and ammonium chloride dissolved in water as filtrate. When the filtrate is heated, water evaporates leaving behind ammonium chloride.
Question-14- (a) It is a hot summer day, PRIYANSHI and ALI are wearing cotton and nylon clothes respectively. Who do you think would be more comfortable and why?
Answer- PRIYANSHI will be more comfortable than ALI. This is because cotton clothes are better absorber of water than nylon. Due to sweat is absorbed faster in cotton clothes which leads to faster evaporation and better cooling.
(b) You want to wear your favorite shirt to a party, but the problem is that it is still wet after a wash. What steps would you take to dry it faster?
Answer- The steps taken will be :
(i) Spreading shirt in air (evaporation increases with increase in surface area.)
(ii) Switching on fan in the room where shirt is spread (increase in speed of wind increases evaporation.)
(iii) Using hot electric iron on clothes (increase in temperature increases evaporation.)
Question-15- Comment on the following statements:
(a) Evaporation produces cooling.
Answer- During the process of evaporation, high energy particles leave the liquid surface taking away heat energy. This leads to cooling effect.
(b) Rate of evaporation of an aqueous solution decreases with increase in humidity.
Answer- Air cannot hold more than a fixed amount of water vapor for a given temperature. When air already has higher amount of water vapor then it will not take up more water vapor. This leads to lesser rate of evaporation.
(c) Sponge though compressible is a solid.
Answer- A sponge can be compressed because it has tiny pores in it in which air is trapped. When the sponge is pressed, the air is expelled out and the sponge gets compressed.
Question-16- Why does the temperature of a substance remain constant during its melting point or boiling point?
Answer- During melting or boiling the heat supplied is used in overcoming the forces of attraction between the particles. Therefore, the physical state changes but the temperature does not.
Question-17- Why does the temperature of a substance remain constant during melting and boiling point?
Answer- Melting and boiling accompanies change of physical state of a substance which needs the constituent particles of the medium to be separated to larger distance against their force of attraction. For this energy is needed. The heat that we supply provides this energy and therefore temperature remains constant.
CLASS-9 SCIENCE CHAPTER 1-MATTER – EXEMPLER QUESTION
