Maharashtra Board Class 9 Science Solution Chapter 14 – Substances in Common Use
Balbharati Maharashtra Board Class 9 Science Solution Chapter 14: Substances in Common Use. Marathi or Science Medium Students of Class 9 get here Substances in Common Use full Exercise Solution.
Std |
Maharashtra Class 9 |
Subject |
Science Solution |
Chapter |
Substances in Common Use |
1.) Fill in the blanks.
Ans:
a) The number of molecules of water of crystallization in soda is 10.
b) The chemical name of baking soda is sodium bicarbonate.
c) Iodine 123 is used in treatment of hyperthyroidism.
d) The chemical name of Teflon is poly tetra fluoro ethene.
2.) Match the pairs.
Ans:
a) Saturated brine: Crystallization of salt
b) Fused salt: Sodium metal freed
c) CaOCl2: Oxidation of colour
d) NaOHCO3: Basic salt
3.) Write answers to the following.
a) What is mean by radioactivity.
Ans:
- Radioactivity is the phenomenon of emission of highly penetrating and energetic radiation from highly unstable nuclei in order to form the stable nucleus.
- In radioactivity, there will be decay of atomic nuclei takes place with emission of radiation such as alpha rays, beta rays and gamma rays.
- The heavy atomic nuclei shows the property of radioactivity like uranium.
b) When is the nucleus is said to be unstable?
Ans:
- The nucleus is said to be unstable when it shows property of radioactivity or decay process. As the nucleus is unstable means it is not neutral one and decayed into another nuclei there by emitting radiation.
- The emitted radiation are highly energetic, penetrating and invisible such as alpha, beta, gamma rays and it is converted into stable nucleus.
- The heavy elements like uranium, thorium are the radioactive elements which shows property of radioactivity and forms the stable nuclei.
c) Which diseases are caused by artificial food colours.
Ans:
In our daily life, we use mostly artificial food colours to make food colourful, attractive and tasty. But regular consumption of these food colour may cause the disease like ADHD mainly in children’s. So we have to avoid more consumption of food colours through cakes, ice-cream, drinks etc. We can use natural food colours instead of artificial food colours.
d) Where in the industrial field is radioactivity used.
Ans:
The phenomenon of radioactivity is related to highly unstable and radioactive elements which are mostly used for creating huge amount of energy in big projects, industries and in nuclear power plant.
Following are the uses of radioactivity in industrial field.
- In nuclear reactors huge amount of energy is created by using radioactive substances as a fuel through the process of nuclear fusion or fission process.
- In most of the industries which are preparing paper, glass and metal sheets the radioactive materials are used to control the thickness of that sheets to maintain their quality.
- Radioactivity phenomenon is also used to get luminous surface in ceramics, metals and utensils also. Thus there will be large use of radioactive substances on industrial level which may harmful to us also.
e) Write down properties of teflon.
Ans:
Following are the properties of teflon.
- As teflon is a water and oil proof hence they doesn’t sticks on the teflon.
- We can use teflon at very high temperature also as it has high melting point and hence we can maintain it at very high temperature also.
- As teflon is inert to atmosphere and also for chemical substances it can’t react with other substances at normal temperature.l
f) What type of colours will you use to celebrate eco-friendly rangpanchami? Why?
Ans:
- Due to the use of artificial colours during rangpanchami which contains hazardous chemicals may cause skin cancer, skin diseases, etching of skin, asthma etc.
- Hence, we have to avoid the use of artificial colours and have to use eco-friendly colours like colours made from spinach, beetroot, gulmohar, different flowers like palash etc.
- Because of the use of this natural colours we are safe and there will be no pollution in the environment occurs.
- To make environment pollution free we have to celebrate eco-friendly rangpanchami.
- It’s our responsibility to make environment pollution free not only for us but for also our next generation also, hence we have to use and advice to others for the use of natural colours to celebrate eco-friendly and safe rangpanchami.
g) Why has the use of methods like teflon coating become more common?
Ans:
- We know that, teflon is not reacting with other elements at normal temperature pressure because it has high melting point and it’s chemical name is poly tetra fluoro ethene (C2F4)n.
- Also, the on articles of materials made from teflon water and oil doesn’t stick easily so it is easy to use teflon coating materials.
- Teflon is a poor conductor of electricity and teflon coated articles are easy to clean.
- Because of all these advantageous properties of teflon the methods like teflon coating becomes more common.
4.) Give scientific explanation.
a) Bleaching powder has the odour of chlorine.
Ans:
As we know that, bleaching powder means calcium oxychloride Ca(OCl)2. As bleaching powder on reacting with CO2 in air it forms the CaCO3 i.e. calcium carbonate and chlorine gas is evolved. Because of this reason when bleaching powder is exposed to air it smells like chlorine or has odour like chlorine.
b) The hard water of well become soft on adding washing soda to it.
Ans:
- The hardness of water of well is mainly due to the presence of chlorides and sulphates of calcium and magnesium in the water of well.
- When we add washing soda in hard water of well, the chloride and sulphates of calcium and magnesium reacts with the washing soda and forms the carbonate salts which are insoluble in water. Because of these salts the hard water become soft and it can be used for domestic purposes.
- The following reaction shows how hard water be converted into water suitable for use.
MgCl2 + Na2CO3 -> MgCO3 + 2NaCl
c) Soap forms a precipitate in hard water.
Ans:
- We know that, when oil or animal fat is boiled with the aqueous solution of sodium or potassium hydroxide then sodium or potassium salts of carboxylic acids which are the fatty acids are formed and these salts are nothing but the soap.
- When we mix soap with hard water containing salts of calcium and magnesium, then calcium and magnesium salts of fatty acids are formed which are insoluble in water and hence it forms the precipitate in hard water.
- Hence, soap forms precipitate in hard water.
d) The particles of powder are given an electric charge while spraying them to form the powder coating.
Ans:
- Powder coating is the method in which a layer of powder is applied which is harder than the paint on the surface of an iron to prevent it from rusting. And the powder is sprayed on the polished surface by the process of electrostatic spray deposition.
- In which electric charge is given to powder and it forms the uniform layer of powder on the metal surface by sticking to it.
- As this type of powder coating method is highly durable, hard and attractive hence the particles of powder are given electric charge while spraying them to form powder coating.
e) The aluminium article is used as an anode in the anodising process.
Ans:
- In the anodising process, a uniform protective layer is formed on the surface of aluminium metal on reacting with oxygen from air.
- In this process electrolysis is done when dilute acid is taken in electrolytic cell and aluminium is used as anode. When we pass current through it then H2 gas is released at cathode and oxygen gas is released at anode which is aluminium article and hence hydrated aluminium oxide is formed on the anode which is the iron article and in this way we can protect the article from further rusting.
f) When the radiation coming out from certain radioactive substance is passed through an electric field, marks are found at three places on the photographic plate placed in its path.
Ans:
Rutherford and Willard discovered the three types of radiation when electrical filed is passed through photographic plate.
- When the radiation coming out from certain radioactive substance is passed through an electric field there will be marks are found at three places on the photographic plate placed in its path. These three marks on the photographic plate are showing the three types of rays emitted from the radioactive substance.
- The rays which are turned slightly towards the negative plate are called as alpha rays having positive charge, high ionising power and high power to produce fluorescence.
- The rays which are turned slightly towards the positive plate are called as beta rays and having negative charge, low ionising power and very low power to produce fluorescence.
- And those rays which travels in the same direction and doesn’t get turned are called as gamma rays which are electrically neutral, having low ionising power and low power to produce fluorescence.
- The three types of marks on photographic plate shows these three kinds of rays.
g) A certain types of ceramic tiles are fixed on the outer layer of space shuttle.
Ans:
- Ceramic is the heat resistant substance which is formed by kneading an inorganic substance in water and after that shaping it followed by hardening on heating.
- As ceramics are heat resistant hence they can withstand at high temperatures also without decomposition.
- They are brittle, water resistant and also electrical insulators. Because of all these advantageous properties of ceramics certain types of ceramic tiles are fixed on the outer layer of space shuttle.
5.) Write answers to the following.
a) Write about artificial food colours, the substances used in them and their harmful effects.
Ans:
- Food colours are natural as well as artificial. The natural food colours are those which are prepared from seeds, beetroot, flowers and fruits and which are not harmful to our health.
- While the artificial food colours are tetrazene, sunset yellow which are used extensively. And over consumption of these food colours may leads to detrimental to health.
- Food colours are in the form is powder, gels, pastes etc. We see that they are added in ice creams, ice candies, sauce, fruit juice, cold drinks, pickles, jams, jelly and also in chilli powder, turmeric, sweets and many more to make them attractive and tasty.
- But these food colours may include small amount of lead and mercury which became very harmful to people which are consuming those food in daily manner.
- Also, due to excessive consumption of food colours through food may cause disease like ADHD i.e. Attention Deficit Hyperactivity Disorder which mainly affects the children.
b) What is mean by water of crystallization? Give examples of salts with water of crystallization and their uses.
Ans:
- The quantity of water molecules present in the one formula of unit salt is called as the water of crystallization. Also we can say that the amount of water molecules which forms the structure of crystal are called as water of crystallization.
- Following are the substances in our daily use which includes the water of crystallization.
Alum, Borax, Epsom salt, Barium chloride, sodium sulphate etc.
- Water of crystallization gives the shape and crystalline structure to it.
c) Write briefly about the three methods of electrolysis of sodium chloride.
Ans:
- The electrolysis of sodium chloride by different methods is explained as below.
- Common salt NaCl is the colourless and crystalline ionic compound and with no water of crystallization in its structure.
- It is neutral salt and salty to taste and mainly used for producing salts like Na2CO3, NaHCO3.
- When we pass electric current through saturated solution of sodium chloride i.e. brine then electrolysis takes place with the evolution of hydrogen gas at cathode and chlorine gas at anode. Mainly this method is used for producing chlorine gas. The chemical reaction occured in this process is as follows.
2NaCl + 2H2O ->2NaOH + Cl2 + H2
- When we heat common salt at high temperature about 800°C it get melted and that state of salt is called as the Fused state of salt.
- When we electrolyse these Fused salt then chlorine gas is released at anode and liquid sodium metal at the cathode.
6.) Write the uses.
a) Anodising
Ans:
In anodising process the protective layer is formed naturally on the surface of aluminium metal when it reacts with oxygen in air.
- Anodising method is used to protect the iron surfaces from rusting.
- The utensils like griddles and cookers which are used for cooking are manufactured by using anodising process also.
- As anodising process protects the iron substances from rusting hence it can be used for maintaining iron substances for long period of duration.
b) Powder coating
Ans:
- Powder coating method is used to apply a later harder than paint on the surface of iron objects to prevent them from rusting.
- As powder coating method is highly durable, hard and attractive hence it can be done on plastic and medium density fibre board in our daily use.
- Powder coating method is also used for formation of long cross linked polymeric chains.
- The heat damage, cold damage and corrosion is resisted in architectural steels by the process of powder coating.
- The outdoor metal products are mostly made by using the method of powder coating.
c) Radioactive substances
Ans:
Radioactive substances are used in various fields because of their properties which are discussed below.
Industrial field:
- In radiotherapy, internal cracks and voids are detected with the help of gamma rays.
- Radioactive substances are used to maintain the thickness, density and level while in manufacturing the aluminium, iron, plastic sheets.
- The radioactive substances like radium, promethium, tritium with some phosphor are used to make objects visible in dark i.e. they are used as luminescent paints and radioluminance.
- Radioactive substances are also used in ceramic articles to luminous them.
In agricultural field:
- The gene and chromosome giving fast growth, productivity are modified by using radiation.
- For food preservation cobalt-60 is used.
- Onions, potatoes are also irradiated with gamma rays to prevent their sprouting.
Medical sciences:
- In polycythaemia the phosphorus 32 is used for treatment.
- In the treatment of bone cancer isotopes of strontium, radium and samarium are used.
- Iodine-123 is used in the treatment of hypothyroidism.
- The small tumours in the body are also detected by using radioactive isotopes.
d) Ceramic
Ans:
Ceramic is heat resistant substance which is formed by kneading an inorganic substance in water and then shaping followed by hardening it by heating.
- Ceramics are used in making roofing tiles, construction bricks and pottery as they are heat resistant.
- As ceramics are water resistant and electrical insulators they are used in electrical instruments for coating their interior of kiln, outer surfaces of ships, and blades of jet engines.
- Also, certain types of ceramic tiles are fixed on the outer layer of space shuttle because of the above discussed properties of the ceramic.
- Also, some types of ceramics are used as superconductors.
7.) Write the harmful effects.
a) Artificial dye
Ans:
- Dyes are the coloured substances which are on applying to particular article gives colour to them. They are soluble in water but insoluble in oil.
- Natural dyes are mainly prepared from plants while in artificial dyes petroleum products and minerals are used.
- There are various adverse effects of use of dye which are given as below.
- Hair dying may cause hair fall, damage to hair texture, burning of skin and also the adverse effects on our eyes.
- Lipstick contains the dye carmine which doesn’t affect the lips but may causes stomach problems.
- While making natural dyes if excessive plant materials are used then it may leads to deterioration of the environment.
b) Artificial food colours
Ans:
- Food colours are natural as well as artificial. The natural food colours are those which are prepared from seeds, beetroot, flowers and fruits and which are not harmful to our health.
- While the artificial food colours are tetrazene, sunset yellow which are used extensively. And over consumption of these food colours may leads to detrimental to health.
- Food colours are in the form is powder, gels, pastes etc. We see that they are added in ice creams, ice candies, sauce, fruit juice, cold drinks, pickles, jams, jelly and also in chilli powder, turmeric, sweets and many more to make them attractive and tasty.
- But these food colours may include small amount of lead and mercury which became very harmful to people which are consuming those food in daily manner.
- Also, due to excessive consumption of food colours through food may cause disease like ADHD i.e. Attention Deficit Hyperactivity Disorder which mainly affects the children.
c) Radioactive substances
Ans:
- The radioactive radiation’s may affect directly to central nervous system.
- When radiation are bombarded on DNA in the body it may leads to hereditary defects.
- Due to penetration of radioactive radiation through skin it may causes the diseases like skin cancer, leukemia.
- Due to explosion some radioactive pollutants are created which may enter through air and hard to control them.
- If there will be radioactive paint on watches then it may cause cancer also.
- Strontium-90 can enter in our body through plants, fruits, flowers, cereals, milk etc and lead to cause the diseases like bone cancer and leukemia.
d) Deodorant
Ans:
- When there will be bacterial decomposition of the sweat then it causes body odour and hence deodorant is used to prevent this odour. It contains parabens and also alcohol in large amount and sometimes aluminium compounds and silica are also used.
- There are various harmful effects of deodorant which are discussed below.
- Aluminium zirconium compounds are the most harmful chemicals in deodorants and it may cause the disorders like headache, asthma, respiratory disorders, heart disease.
- Due to aluminium chlorohydrates there will be possibility of various skin disorders and also the skin cancers.
8.) Write the chemical formula.
Ans:
a) Bleaching powder: Calcium oxychloride Ca(OCl)2
b) Common salt: Sodium chloride NaCl
c) Baking soda: Sodium bicarbonate NaHCO3
d) Washing soda: Sodium carbonate Na2CO3
9.) Explain what you see in the following picture.
Ans:
- Above picture shows the method of powder coating in which polymer resin and other pigments are melted, mixed, cooled and then converted into powdered form which is throughout uniform.
- In this method, particles of powder are given an electrostatic charge so that a uniform powder layer is formed which sticks to the metal surface.
- After that object is heated in the oven along with the coating and hence long cross linked polymeric chains are formed.
- This powder coating method is highly durable, hard and also attractive and hence has vast of applications.