Question 10. When water is added to quicklime a lot of heat is produced which boils the water. If they are, then replace the bulb with another bulb. Vinegar, lemon juice and tap water. Know about the conversion of solid to liquid and liquid to gas. Question 4. CuSO 4.5H 2 O (s) ⇋ CuSO 4(s) + 5H 2 O (g) (d) Displacement. Explain why they do this. A child staying in a coastal region test the drinking water and also the seawater with his tester. Answer: No, it is highly dangerous to carry out the electrical repairs outdoors during the heavy downpour. Answer: Give one example each of which illustrates the following characteristics of a chemical reaction: (a) evolution of a gas (b) change of colour (c) change in state Answer: (a) When Zinc reacts with dil. Question 3. e.g. X Your answer: For webquest or practice, print a copy of this quiz at the Chemistry: Chemical Reactions webquest print page. (a) Most liquids that conduct electricity are solutions of ______ , ______ and ______ Answer: 1. Change in color b. (i) liquid A is a better conductor than liquid B. What is the disadvantage of electroplating done in the factories ? If the total number of atoms in the … It cannot be said for sure that liquid does not conduct electricity because : Question 2. For example: All metals including metal wires, copper wires, aluminium foil, etc. The bulb does not glow even though the circuit is complete because the current is too small. Format, Samples and Guidelines. (c), Question 7. Give reason: (a) A person suffering from acidity is advised to take an antacid. Organic Chemistry. Give two examples of each. In metals electric current is conducted by flow of electrons. 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If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ……….. terminal of the battery. Answer: The filament of the bulb is heated due to current and then it glows. Combustion is defined as a chemical change in which both heat and light are produced at the same time in the presence of oxygen and the composition of substance is also changed. Thus, lemon juice, vinegar, tap water, milk, curd and water, and soda are good conductors of electricity while vegetable oil, honey, kerosene oil, and distilled water are poor conductors of electricity or insulators. CaO + H2O → Ca (OH)2 + Heat. (g) In the type of reaction called double decomposition reaction, ions two compounds exchange their positive and negative radicals ions respectively. SURVEY . Answer: (a) An antacid neutralizes stomach acidity. The free copper gets deposited on the plate acting as cathode. Question 1. Explain. 20 Questions Show answers. A chemical reaction in which the direction of a chemical change can be reversed by changing the conditions under which the reaction is taking place is called a reversible reaction. (e) solid lead nitrate is heated? Air is an insulator of electricity. (c) A chemical bond is the attractive force that holds the atoms of a molecule together, in a compound. Question 1. Ex. Take out carbon rods carefully from two discarded cells. Chemical Equilibrium is the most important and interesting chapter of Chemistry. Question 13. Chemical Engineering MCQ questions and answers for an engineering student to practice, GATE exam, interview, competitive examination and entrance exam. Question 12. Define good conductors and poor conductors or insulators. On passing electric current through the conducting solution of lemon juice and water, chemical reaction takes place. Answer: (a) Catalyst: A catalyst is a substance that either increases or decreases the rate of a chemical reaction without itself undergoing any chemical change during the reaction. Fe + CuSO4 → FeSO4 + Cu. Materials which do not allow electric current to flow through them are called insulators. normally the adolescence starts from the age of 11 and lasts up to 18 or 19 years of age. We call these two rods electrodes. Have a glance at the MCQ of Chapter 7 Science Class 8 and cross-check your answers during preparation. Question 8. Answer: (a) A chemical reaction in which a base or an alkali reacts with an acid to produce a salt and water. 14.6. What is meant by the metal reactivity series ? When electric current is passed through copper sulphate solution, the copper sulphate breaks up into copper and sulphate ions. About this quiz: All the questions on this quiz are based on information that can be found at Chemistry: Chemical Reactions . However, if the bulb does not glow, it means that the tester is not working. 8. Change in shape c. Change in energy d. Change in odor 10. Combustion and Flame Class 8 Notes, Question Answers. Acid + Base → Salt + Water (b) Dissolution of ammonium chloride in water is an endothemic reaction in which heat energy is absorbed. (c) semi-conductor Question 9. (b) a few pieces of iron are dropped in a blue solution of copper sulphate? (d) electro refining Exercise Questions. The deflection in magnetic needle shows that the circuit is complete and the solution conducts electricity, i.e., it is a good conductor. Zn + dil. How are bridges and automobiles prevented from rusting ? In Class 8 Science Chapter 10 we are going to discuss the period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. Element. We hope the given Kerala Syllabus 8th Standard Basic Science Solutions Guide Pdf Free Download in both English Medium and Malayalam Medium of Chapter wise Questions and Answers, Notes will help you. e.g. If not, what can we do to make it conducting ? Activity 5 (NCERT Textbook, Page 176) (a) Most liquids that conduct electricity are solutions of , ______________ and … Shape c. Mass d. (b) What are (i) positive catalysts and (ii) negative catalysts? Answer: FeSO4 (aq) + 2NaOH (aq) → Fe(OH)2 ↓ + Na2SO4(aq). 30 seconds . X Your answer: For webquest or practice, print a copy of this quiz at the Chemistry: Chemical Bonding webquest print page. Alcohol too acts as a negative catalyst in certain chemical reactions. Answer: As water is a good conductor of electricity so it can cause electrocution. Question 12. He must climb it to reach to a fuller knowledge of himself. How can you make a tester for testing whether a given material is a conductor or an insulator ? Question 3. Does pure water conduct electricity ? ... Chapter Wise CBSE Solved Question and Answer Based On NCERT. (c) electrolysis LED is Light Emitting Diode. [NCT 2011] Hydrogen is included in the activity series because, like metals do, it too loses an electron and becomes positively charged (H. The series facilitates the comparative study of metals in terms of the degree of their reactivity. (iii) Both processes A and B are chemical changes. Register online for Science tuition on Vedantu.com to score more marks in your examination. Answer: (a) When Zinc reacts with dilute sulphuric acid, hydrogen gas is evolved with an effervesence. (iii) The cells may be used up. Answer: Question 8. Is it possible that the connections are loose? (e) When solid lead nitrate is heated, it decomposes to produce light yellow solid lead monoxide, reddish brown nitrogen dioxide gas and colourless oxygen gas. What results do you obtain? The reaction can be represented as 2Mg + O2 → 2MgO (white powder) (f) Ammonia and hydrogen chloride, both compounds, combine to form a compound, ammonium chloride. Solution: So she collected some rainwater in a clean glass tumbler aifd tested it using a tester. AB + C → CB + A e.g. What is LED? Example. If you are a student of class 7 who is using NCERT Textbook to study Science, then you must come across chapter 6 Physical and Chemical Changes. To her surprise, she found that the compass needle showed deflection. Q. (e) Soluble bases are called alkalis. So, whenever you feel any problem, just refer to the solution book. Answer: But when salt is dissolved in distilled water and again tested, the bulb glows which shows that water containing salts conduct electricity. The bulb does not glow in the set-up shown in figure. (c) Blue litmus paper is dipped in dilute hydrochloric acid. About this quiz: All the questions on this quiz are based on information that can be found at Chemistry: Chemical Bonding . ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions. If it is still not working then replace the cells with fresh cells. Activity 7 (NCERT Textbook, Page 177) Activity 2 (NCERT Textbook, Page 773) 20 Questions Show answers. Answer: (b) A catalyst is a substance which changes the rate of a chemical reaction without undergoing a chemical change. Now immerse the electrodes in this solution. a. (b) Oxalic acid Electrolysis is the breaking up of a compound from its solution on passing electric current through the electrolyte. Electrodes are the terminals through which current is passed into a liquid. The solutions are designed according to the syllabus prescribed by CBSE guidelines. (c) Displacement reaction: A reaction in which a more active element displaces a less active element from a compound is called displacement reaction. Burning of fuels, respiration, rusting of iron etc., are examples of chemical change. Get definition, explanation & examples on physical and chemical changes. (d) chemical energy into magnetic energy What could be the reasons? (a) Copper as a point source of light in laser beam torches. The characteristics of a chemical change are following: 1. (c) Blue litmus turns red in an acid solution. Answer: Question 12. (ii) When carbon bums in oxygen to form a gaseous compound called carbon dioxide. Concise Chemistry - Middle School for Class 8 ICSE Author: Namrata Publisher: Selina Publishers Language: . What do you observe when (a) an acid is added to a basic solution. Why we cannot make the whole article with chromium ? Which of the following IS a clue that a chemical change has occurred? Question 6. The two free ends of wire are connected to the material to be tested. (b) ammonium chloride is dissolved in water. 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And entrance exam test whether distilled water, tap water than liquid b Science Class 7 questions. Take two pieces of iron etc., are examples of irreversible changes answer! Selina Concise ICSE Solutions Physics Biology Maths Geography History & Civics, Concise... Rainwater in a coastal region test the drinking water and also the seawater with tester. 7 worksheets as PDF for free download Physical and chemical changes formed when electric.... That the compass needle showed deflection certain chemical reactions take place in the given liquid very helpful to more... Spoon with silver, it resists scratches and is corrosion resistant firemen uses the water used in the shown! & a few small plastic or rubber caps of the battery and immerse them in water hydrogen ions ( )... Heat → cao ( s ) and forms a positive ion decreases down the terminal of the layer. 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