Name the phenomenon involved. We know that boiling point of water is 100°C and since acetone is more volatile it will separate out first. Chlorine gas, iron, aluminium, iodine, carbon, sulphur powder. Question 2. Answer: Describe any three properties of colloid. Why is it not possible to distinguish particles of a solute from the solvent in solution? [NCERT Exemplar] (d) Centrifugation (ii) Mixtures of chalk powder with water and milk with water. A solution of urea in water contains 16 grams of it in 120 grams of solution. The elements are sulphur and neon. Filter the solution. Identify colloids and true solutions from the following: Answer: Question 4. (d) Iron sulphide mixture and volatilize the components, a condenser to cool the vapors back to Hence, a colloidal solution cannot be separated by filtration. Sample ‘A’ boils at 100°C and sample ‘B’ boils at 102°C. flat-bottomed one for smoothness of boiling.� Sand is a loose granular material consisting of finely divided rocks and other mineral particles. ����������� The Let it stand undisturbed for sometime so that separate layers of oil and water are formed. Answer: Define chromatography and give its one application. What are the two components of a colloidal solution? Pond water, fog, aluminium paint, vinegar and glucose solution. (iv) Mixture of chalk powder and water. Question 6. (i) Sulphur powder The only difference is that the dispersed phase in fog is liquid and in smoke it is a solid. Answer: Question 9. Answer: The different constituents of the mixture have different affinities for the stationary phase. An unknown substance ‘A’ on thermal decomposition produces ‘B’ and ‘C’. (b) Same results were not observed with a salt solution. Compounds – Pure sand, Ice, CaO, Ammonia gas standard taper glass connections. (c) It is a chemical change because combustion of kerosene occurs and new products are formed. They were amazed to see that milk taken in the tumbler was illuminated. Explain why filter paper cannot be used to separate colloids. A practical investigation on the factors that affect the evaporation of propanone. Distillation is used to get back acetone. It is collected as residue. It is a pure substance because chemical composition of sugar crystals is same irrespective of its source. (b) Initially the water will evaporate and then sugar will get charred. Solid mixture of sand and common salt take the colours of the two. Why is water called universal solvent? They scatter light passing through them making its path visible. In association with Nuffield Foundation. Question 12. Mass of solution = 250g (a) Explain why the milk sample was illuminated. An element cannot be split by physical or chemical methods. Distinguish between physical change and chemical change. What stays the same? Answer: (b) Potassium chloride and ammonium chloride Suggest separation technique (s) one would need to employ to separate the following mixtures: \(\mathrm{Fe}(s)+\mathrm{S}(s) \quad \stackrel{\mathrm{Heat}}{\longrightarrow} \quad \mathrm{FeS}(s)\) Question 13. If so, write the chemical equation involved. They can be separated by fractional distillation. Classify the following into elements, compounds and mixtures. (iii) Diamond Will it be a pure substance or a mixture? The transport of salt ions by the Nernst-Planck theory is analogous to the case of (monopolar) ion-exchange membranes, and has been the subject of many studies on electrodialysis [250,251]. (i) Germanium [NCERT Exemplar] Comment. ����������� One last (c) Coloured gemstone (d) Separation by using separating funnel to separate kerosene oil followed by evaporation or distillation. not react, melt or evaporate and contaminate the product. (a) Sublimation (ii) would show Tyndall effect? Answer: Question 3. (ii) Name the technique used by the child. 0.5 g of salt is dissolved in 25 g of water. (c) An acetone bottle is left open and the bottle becomes empty. involve rubber or cork stoppers but in more modern apparatus standard taper connections They can be separated only by electrolysis. They do not settle down when left undisturbed. Solution: Therefore, sea water is considered homogeneous. Classify the following as physical or chemical properties: Question 8. liquid state, and a collection vessel.� Click (vi) CaO. Iodine is the solute and alcohol is the solvent. Answer: [NCERT Exemplar] It is composed of two different elements, hydrogen and oxygen which cannot be separated by physical methods. Answer: (b) Dissolution/diffusion Physical properties—(a) and (c) Question 11. [NCERT Exemplar] Question 14. (a) Drying of a shirt in the sun. The teacher instructed three students A’, ‘B’ and ‘C’ respectively to prepare a 50% (mass by volume) solution of sodium hydroxide (NaOH). some impurities may remain dissolved in the solution even after filtration. [NCERT Exemplar] Part A Answer: Mass of salt present = 0.5 g [NCERT Exemplar] If a beam of light is put on a milk sample contained in a beaker, the path of light beam is illuminated and becomes visible when seen from the other side. Removing sand by filtration Make a solution of sand and sodium chloride in water. Chromatography is a technique used for the separation of a mixture of solutes brought about by distribution of dissolved material between two immiscible phases, one of which is mobile phase and the other part is stationary phase. Volume of solution = (12 + x) mL Answer: Answer: broken.� Always allow for a pressure Metalloids – Germanium, boron. (b) Rising of hot air over a radiator. (i). Classify each of the following as a physical or a chemical change. To absorb more heat, cold water is passed from lower side so that it will stay for longer time and absorb more heat from the vapours to form liquid state of the substance. A solution has been prepared by mixing 5.6 mL of alcohol with 75 mL of water. (a) Fog (g) Carbon a distillation apparatus which uses rubber stoppers rather than the more modern Mass by volume per cent = \(\frac{\text { Mass of solute }}{\text { Volume of solution }} \times 100\) Take the mixture in a petri dish and roll a bar magnet over it. Identify the elements from the following substances: sulphur, brine, hydrochloric acid, water, neon, paper, sugar. Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do. 18. Separating sand and salt by filtering and evaporation. On filtration, a residue of insoluble soil does not pass through the filter paper. Evaporation. = 550 g. Question 5. (d) Change in the colour of black tea on adding lemon juice to it. some solids decompose or get charred on heating to dryness. Calculate the mass of sodium sulphate required to prepare its 20% (mass per cent) solution in 100 g of water. Question 14. Removing ammonium chloride by sublimation Transfer the remaining mixture into China dish and heat it. Question 12. Mass of solution = 120 g, Question 3. (c) Iron Give its one application. (a) Iodine If not, explain. ����������� The Identify the dispersed phase and dispersing medium in the following colloids. Calculate the mass of water and glucose required to make 250 g of 40% solution of glucose. Answer: the flask and gets out of control. Answer: Open the stopcock of the separating funnel and pour out the lower layer of water carefully. (a) Solid potassium chloride will separate out. (c) a mixture of iron filings and sulphur powder is heated strongly? Answer: distillation flask before heating has begun.� It is very important not to add chips or How can you change a saturated solution to an unsaturated solution without adding any more solvent to it? Water is known as universal solvent because it has the ability to dissolve wide variety of substances. ‘Sea water can be classified as homogeneous as well as heterogeneous mixture.’ Comment. Answer: Question 2. (b) Can you prepare one acidic and one basic solution by using the products formed in the above process? (ii) Boron (d) Name a non-metal which is known to form the largest number of compounds. Question 6. ����������� Distillation (c) Can a solution be heterogeneous? Question 5. Answer: condenser must generally be connected to a source of running water to provide heat source.� Heating mantles or sand (b) an aqueous sugar solution is heated to dryness? A solution is said to be diluted, concentrated or saturated on the basis of the amount of solute dissolved in the solution. By heating the saturated solution, it becomes unsaturated. Answer: (b) Name a non-metal which exists as a liquid at room temperature. This scattered light enters our eyes and we are able to see the path of light beam. on the blue link distillation It is a process that separates a pure solid in the form of its crystals from a solution. Show diagrammatically how water is purified in the waterworks system and list the processes involved. They cannot be distinguished even under a microscope. Mass of salt present in the solution = 20 g Name the process associated with the following: Colloid – air bubbles Suspension – clay particles. This is because the colloidal particles are big enough to scatter light falling on them. (c) Filtration to separate sand followed by evaporation/distillation Name two elements which exist in liquid state at room temperature. (a) Chemical change. Close the stopcock of the separating funnel as the oil reaches the stopcock. What is mass per cent of a solution? Question 6. Iron filings and sulphur were mixed together and divided into two parts ‘A’ and ‘S’. Whose mixture: are used.� If stoppers are used, it must completely sealed system.� When the (a) It is a physical change because water is converted from its liquid state to gaseous state because of the sun’s heat. Question 15. Give reason in support of your statement Mixture – Air, Glass. Sulphur remains unreacted. The voltage across a BPM can be calculated via the Nernst equation. (i) would not leave residue on filter paper after filtration? So, the mass of sodium sulphate required is 25 g. Question 7. Answer: cooling for the vapors.� The proper Answer: We can separate two miscible liquids by fractional distillation, if both the liquids have difference in their boiling points. eAuditNet is web-based software that supports and improves efficiency in the auditing and accreditation systems of industry managed programs administered by the Performance Review Institute. They tried the same activity by taking a salt solution but found that light simply passed through it. While diluting a solution of salt in water, a student by mistake added acetone (boiling point 56°C). Question 7. (i) Pure sand NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12, Extra Questions for Class 9 Science Chapter 2 Is Matter Around Us Pure. Crystallisation is considered better than simple evaporation because. Name the allotrope. Question 10. A group of students took an old shoe box and covered it with a black paper from all sides. The physical and chemical properties of hydrogen and oxygen are entirely different from the properties of water. boiling smoothest, boiling chips or tubes should be added to the liquid in the The mass of solution would be = (x + 100)g Question 1. (c) Evaporation/diffusion Describe the procedures you would use to separate these constituents from the mixture. the heated flask and the outflow hose nearest the heated flask.� This prevents the hottest vapors from This process is used to obtain wines from the sugarcane juice. Question 2. Classify the following into metals, non-metals and metalloids: (b) salt (density of water = 1 g /mL). A simple practical on separating salt, sand and iron filings based on physical properties. apparatus. be known that the hot vapors will not react with the rubber or cork and thus should be secured to a stable stand or rack to prevent it from falling Question 8. loosely in the receiving flask. Give two points of differences between an element and a compound. to bubbles and sometimes foaming that is constricted in the narrowing part of Answer: State the principle of separating two immiscible liquids by separating funnel. Question 7. (a) Fog—liquid, gas How will you identify the gases evolved? = \(\frac{50}{100} \times 100\) = 50% mass by volume. Evaporate the filtrate to dryness to get sodium chloride or by crystallisation. Answer: Question 1. \(12=\frac{12}{12+x} \times 100\) Answer: Mass of solution = Mass of glucose + Mass of water Volume of water = 75 mL Question 7. (e) Name a non-metal other than carbon which shows allotropy. Question 1. [NCERTExemplar] (e) Churning of milk cream to get butter. ∴ Percentage amount of the salt = \(\frac{0.5}{0.5+25} \times 100\) = 1.96%, Question 2. Explain. Non-metals – Diamond, iodine and helium They cannot be separated by the process of filtration, (any three points). Solution: 2. Question 5. Answer: Question 5. that they will not come loose if the water pressure should increase during the Solution: If not, explain. Answer: Question 3. 1 Comment. (ii) Air (a) Is this a physical or a chemical change? Calculate the percentage amount of the salt in the solution. (c) Detergent solution, sulphur solution. [NCERT Exemplar] Question 9. Question 6. It is useful in forensic science to detect and identify trace amounts of substances in the contents of bladder or stomach. Question 7. Answer: must be sufficient to accomplish condensation without being so fast as to cause ����������� Heating the Explain using a diagram. What would you observe when = 250g – 100g = 150g. It is defined as the mass in grams of the solute present in one hundred grams of a solution. (v) Copper Answer: 1. Gallium and mercury exist in liquid state at room temperature. (a) Under which category of mixtures will you classify alloys and why? Question 6. Is water an element or a compound? 1. Select from amongst these one example each of a solvent, a solute, a colloid and a suspension. [NCERT Exemplar] The volume of water content of a fine-sand soil is θ = 0.20 m 3 m −3. apart.� This generally causes vapors to Question 1. Question 3. (iv) Ice contacting the coldest water and creating a large thermal shock to the Solution: contaminate the products.� If standard (c) Iron sulphide will be formed. We perform the salt water wash of the hexane mixture, by simply pouring the salt water and hexane into the separatory funnel together in about equal parts and shaking well and burping, before allowing the mixture to … ����������� Many of the (f) Scattering of light (Tyndall effect). Question 4. (c) Can you suggest two more solutions which would show the same effect as shown by the milk solution? (d) Most metal oxides form alkalis on interacting with water. [NCERT Exemplar] Fe(s) + S(s) + 2HCl(aq) → FeCl2(aq) + H2(g) H2S gas formed has a foul smell and on passing through lead acetate solution, it turns the solution black. Sample ‘B’ will not freeze at 0°C because it is not pure water. Question 2. baths are good sources of heat to conform to the round-bottomed flasks.� Care must be taken not to let any vapors near [NCERT Exemplar] Question 7. Give reasons. Which of the following are physical changes? Distinguish between metals and non-metals. (iii) Mixture of common salt and water. Answer: Question 13. [NCERT Exemplar] (v) Mixture of chalk powder and water. [NCERT Exemplar] Numericals Answer: Two liquids ‘A’ and ‘B’ are miscible with each other at room temperature. Describe an activity with diagram to separate a mixture of water and kerosene oil. Total mass of the solution = (30 + 20 + 500)g tight one using a stopper or standard taper connection.� This must NOT be done as it creates a The solute and solvent particles are very small. Describe an activity with diagram to separate a mixture of water and kerosene oil. (a) The composition of a sample of steel is 98% iron, 1.5% carbon and 0.5% other elements. The mixture containing sand and sodium chloride left behind in the China dish. Metal – Copper (d) It is a chemical change because there is a reaction between the citric acid in the lemon and the compounds of tea resulting in formation of new products. At 1 atm, the boiling point of pure water is 100°C and the freezing point of pure water is 0°C. A compound can be split into new substances by chemical methods. (d) Kerosene oil, water and salt. He marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in figure. You are given two samples of water labelled as ‘A’ and ‘B’. [NCERT Exemplar] Sodium chloride will dissolve in water and sand is left as residue on the filter paper. The fractionating column packed with glass beads provides a surface for the vapours to collide and lose energy so that they can be quickly condensed and distilled. Answer: In what way are they different? Hydrogen gas burns with a pop sound. (b) A solution is always a liquid. .� Below is another picture of (b) Salt solution is a true solution. ... water and sand (d) Kerosene oil, water and salt. [ NCERT Exemplar] Answer: Let the mass of sodium sulphate required be x g. The scattering of light by colloidal particles is known as Tyndall effect. CO2 + H2O → H2CO3 (acidic solution), Question 8. ����������� The Also, length of the column would increase the efficiency of separation. Which sample of water will not freeze at 0°C? something like copper wire is twisted around the tubing at the joint to prevent (v) Glass it from coming away.� The flow of water The flask should never be more than half-filled with the liquid mixture can change during the day after they have initially been set. (b) Acidic and basic solutions can be prepared by dissolving the products of the above process in water. Chemical properties—(b) and (d).
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