The Class 9 is an important year in a student’s life and Maharashtra State Board Science is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 9 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 9 Science Book syllabus.
1. Match the Pairs
| Group A | Group B |
| Saturated brine | sodium metal freed |
| Fused salt | basic salt |
| CaOCl2 | crystallization of salt |
| NaHCO3 | oxidation of colour |
Answer:
| Group A | Group B |
| Saturated brine | crystallisation of salt |
| Fused salt | Sodium metal freed |
| CaOCl2 | oxidation of colour |
| NaHCO3 | basic salt |
2. What is meant by radioactivity?
Answer: Elements like thorium, radium and uranium that have a high atomic number and spontaneously emit invisible, highly penetrating radiation of high energy. This property of these elements is known as radioactivity.
3. When is the nucleus said to be unstable?
Answer: The nucleus of radioactive elements is said to be unstable because radiation occurs only from an unstable nucleus.
4. Which diseases are caused by artificial food colours ?
Answer: Tetrazene, sunset yellow is artificial food colours that are used extensively. Over-consumption of artificial food colours can be detrimental to health. Food colours that are added to pickles, jam and sauce may contain small quantities of lead and mercury, which can be harmful for those who consume these products on a regular basis. Consumption of foods with added food colours causes diseases such as ADHD (Attention Deficit Hyperactivity Disorder) in children.
5. Where in the industrial field is radioactivity used?
Answer: Radioactivity is used the industrial field as follows:
Radiography – Gamma rays from the isotopes like cobalt-60, iridium-192 are used in the radiography camera to detect the Internal cracks and voids in cast iron articles and iron solder. This technique is applied to detect flaws in metal work.
Used to Measure thickness, density and level in the manufacture of aluminium, plastic, iron sheets of differing thickness. A radioactive substance is placed on one side in the manufacturing process and an instrument to measure the radiation on the other. Material inside the packing can is also examined using the same technique.
Luminescent paint and radioluminescence – The radioactive substances such as radium, promethium and tritium with some phosphor are used to manufacture certain objects visible in the dark. These include the hands of a clock and certain other objects. Krypton-85 is used in HID (High Intensity Discharge) lamps, while promethium-147 is used in portable X-ray units as the source of beta rays.
Use in Ceramic articles – Luminous colours are used to decorate ceramic tiles, utensils, plates and so on. Earlier, uranium oxide was used in these paints.
6. Write down properties of teflon.
Answer: Given below are certain properties of teflon:
1. There is no effect of the atmosphere and chemical substances on Teflon
2. Neither water nor oil stick to articles that are coated with Teflon
3. Teflon has a melting point of 3270 C and so high temperatures do not affect it
4. It is very easy to clean teflon coated articles
7. What type of colours will you use to celebrate eco friendly Rang Panchami? Why?
Answer: It is advised to use natural colours for Rang Panchami made from natural resources like beetroot, flowers of flame of forest, spinach, flame tree (gulmohar) to protect our health. It is seen that the artificial colours, especially the red colour used during rang panchami contains a high proportion of mercury in it, which poses risks such as skin cancer, blindness, asthma, permanent blocking of sweat pores, itching of the skin and so on. Hence, artificial colours should only be used cautiously.
8. Why has the use of methods like Teflon coating become more common?
Answer: The use of methods like Teflon coating for cooking utensils and industrial equipment has become more common to avoid sticking.
9. Bleaching powder has the odour of chlorine. What is the scientific explanation?
Answer: Due to the carbon dioxide in air, bleaching powder undergoes slow decomposition and chlorine gas is released. So, bleaching powder has the odour of chlorine.
10. The hard water of a well becomes soft on adding washing soda to it. Why?
Answer: The hard water of a well becomes soft on adding washing soda, as is evident from the lather that is formed. It is the presence of chlorides and sulphates of calcium and magnesium that results in the hardness of water. So, Na2 CO3 or washing soda is added to it, this softens the water, thus making it more suitable for use. The reaction with washing soda also produces insoluble carbonate salts such as magnesium and calcium.
MgCl2 (aq)+ Na2 CO3 (s) ® MgCO3 (s) + 2 NaCl (s)
11. Soap forms a precipitate in hard water. Give the scientific reason for this.
Answer: On mixing soap with hard water the calcium and magnesium salts of fatty acids are produced. These are water insoluble and so will form a precipitate instead of forming a lather.
12. The particles of powder are given an electric charge while spraying them to form the powder coating. Give reason.
Answer: The particles of the powder are given an electrostatic charge so that a uniform layer of the powder sticks to the metal surface.
13. The aluminium article is used as an anode in the anodising process. State a reason.
Answer: The aluminium article is used as an anode in the anodising process. When an electric current is passed hydrogen gas is released at the cathode and oxygen gas at the anode. During anodizing, a reaction with the oxygen occurs forming a layer of hydrated aluminium oxide on the anode, i.e. the iron article.
14. A certain type of ceramic tiles are fixed on the outer layer of a space shuttle. Justify.
Answers: Ceramics can withstand high temperatures without decomposing. It is also brittle, water resistant and is an electrical insulator. Henceforth, it is used in electrical instruments to coat the interior of a kiln, the outer surfaces of ships and blades of jet engines. The outer layer of a space shuttle comes equipped with a certain type of ceramic tile.
15. What is meant by water of crystallization? Give examples of salts with water of crystallisation, and their uses.
Answer: Ionic compounds are crystalline in nature and are formed as a result of definite arrangement of ions. In the crystal of some compounds, water molecules are also included in the arrangement. This is known as water of crystallization. We use various salts, which contain water of crystallisation. They include Epsom salt (Magnesium sulphate MgSO4 .7H2 O), Barium chloride (BaCl2 .2H2 O), Alum (Potash alum –K2 SO4 .Al2 (SO4 )3 .24H2O) and so on. Alum is used in the process of water purification. Blue vitriol is used in the blood test for diagnosing anaemia. In the Bordeaux mixture used as a fungicide on fruits like grapes, muskmelon, slaked lime it is used with blue vitriol.
16. Write briefly about the three methods of electrolysis of sodium chloride.
Answer: Given here are the three methods of electrolysis of sodium chloride:
1. A saturated solution of sodium chloride is electrolysed by passing electric current through it. This releases hydrogen gas at the cathode, while chlorine gas is generated at the anode. This is the method used for production of chlorine gas. During the process, an important basic compound NaOH is formed in the cell.
2.The salt melts, when it is heated to a high temperature (about 8000 C). This is said to be the fused state of the salt.
3. Electrolysing the fused salts releases the chlorine gas at the anode and liquid sodium metal at the cathode.
17. What are the uses of anodising?
Answer: Anodising is used to protect iron articles from rusting. It is also the process used to manufacture anodised cooking utensils like griddles and cookers and so on.
18. What is a Ceramic?
Answer : It is a heat resistant substance that is used to make Pots, Mangalore roofing tiles, construction bricks, pottery, terracotta articles and so on.
19. What is the chemical formula for:
a) baking soda
b) washing soda
c) bleaching powder
d) common salt
Answer: Given here is the chemical formula for these :
a) baking soda-NaOHCO3
b) washing soda-Na2 CO3 .H2 O
c) bleaching powder- CaOCl2,
d) common salt- NaCl
20. What is the use of a deodorant?
Answer: Bacterial decomposition of the sweat causes body odour and deodorant is used to prevent this odour. Fragrant deodorant helps you to remain fresh the whole day.
21. What are the harmful effects of deodorant?
Answer: Given here are some of the harmful effects of deodorant:
1. One of the most harmful chemicals found in the deodorant is the Aluminium-Zirconium compounds. This could cause disorders such as asthma, heart disease, respiratory disorders, headache and so on.
2. Aluminium carbohydrates in it cause various skin disorders and also skin cancer.
22. What are some of the ingredients found in deodorant?
Answer: Deodorants contain parabens (methyl, ethyl, propyl, benzyl and butyl) and also alcohol in large proportions. Aluminium compounds and silica are also used.
23. What are simple salts?
Answer: Simple salts are the ionic compounds that do not contain H+ and OH– ions and contain only one kind of cation and anion. For example, Na2 SO4 , K3 PO4 , CaCl2 .
24. Name the important salts found in seawater.
Answer: The important salts found in seawater are:
1. Sodium chloride
2. Magnesium chloride
3. Magnesium sulphate
4. Potassium chloride
5. Calcium carbonate
6. Magnesium bromide
25. What are the uses of baking soda?
Answer: Baking soda is basic in nature and so is used to reduce acidity in the stomach. Other uses include, making bread, cake and dhokla, used to produce the active substance CO2 in the fire extinguisher and to clean the oven.
26. What is chlorine gas?
Answer : A strong oxidizing agent with a strong disinfecting as well as bleaching action is known as chlorine gas.
27. What is the chemical name of bleaching powder?
Answer: The chemical name for bleaching powder is calcium oxychloride. It is a yellowish, white coloured substance.
28. Which are the three types of radiation given out by radioactive substances?
Answer: Three types of radiation given out by radioactive substances are alpha, beta and gamma rays.
29. How is Polycythemia treated?
Answer: The red blood cell count increases in the disease polycythemia. Phosphorus- 32 is used in its treatment.
30. What is used for tumor detection?
Answer: Boron-10, iodine-131, cobalt-60 are used for treating brain tumour, whereas arsenic-74 is used to detect small tumours in the body.
On learning the subject thoroughly, students can refer to the question papers and solutions in order to prepare most competently for the exams. Stay tuned and get updates!