Class 9 MAHARASHTRA STATE TEXTBOOK BUREAU Solutions Science Chapter 14 - Substances in Common Use

a. The number of molecules of water of crystallization in washing 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 polytetrafluoroethene.

a. Radioactivity: radioactivity is a nuclear phenomenon. It is the process of spontaneous emission of α or β and Υ radiations from the nuclei of atoms during their decay.

Example: uranium, radium.

b. A nucleus of atom can be stable or unstable depending on the presence of extra neutrons in their nuclei. The unstable nucleus of an atom can emit various types of radiations. Alpha, beta and gamma rays are given out by radioactive substances which has unstable nucleus.

c. Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children due to excessive consumption of foods with added food colours.

d. Radioactivity has various industrial application:

(i) Radiography: Isotopes like cobalt-60 or iridium-192 are used in camera to find out the internal cracks and voids in cast iron articles.

(ii) It is used in measurement of thickness, density and levels in manufacturing of aluminium, plastic iron sheets of different thickness.

(iii) Some radioactive substances shows properties like luminescent which means them visible in dark. 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.

(iv) Uranium oxide used as a luminious colour to decorate ceramic tiles, utensils, plates etc.

e. Properties of Teflon:

1. Teflon is resisted towards atmosphere and chemicals

2. It is act as a non-stick towards oils or water.

3. Teflon has high melting point hence high temperature does not affect it.

f. If we used artificial colours on Rangpanchami, it will have bad effects on skin n eyes. It can can caused blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores, etc. Therefore, it is necessary to use eco-friendly colours. We can prepare natural colours from natural resources such as beet root, flowers of flame of forest, spinach.

g. The use of methods like Teflon coating became more common because of the miscellaneous properties of Teflon. Teflon is resisted towards atmosphere and chemicals. It is act as a non-stick towards oils or water. Teflon has high melting point hence high temperature does not affect it.

a. When bleaching powder is left exposed in air it reacts with carbon dioxide present in air to form calcium carbonate and releases chlorine gas.

CaOCl₂ + CO₂ → CaCO₃ + Cl₂

b. The hardness of hard water is due to the presence of chlorides and sulphates of calcium and magnesium. When washing soda or soda ash is added to hard water, the corresponding insoluble carbonates settle down and can be removed by filtration.

Ca(HCO₃)₂ + Na₂CO₃ CaCO₃ + 2NaHCO₃

Mg(HCO₃)₂+ Na₂CO₃ MgCO₃ + 2NaHCO₃

c. Hardness of water is due to the presence of calcium and magnesium salts. These ions form insoluble calcium and magnesium soaps when sodium or potassium soaps are dissolved in water. The insoluble soap separates as scum in water and are useless as cleansing agents.

d. In Powder coating method, the particles of the powder are given an electrostatic charge due to which a uniform layer of the powder sticks to the metal surface.

e. During anodising, a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid. The oxygen gas evolved at the anode reacts with aluminium to make a thicker protective oxide layer. This oxide layer can be dyed easily to give aluminium articles an attractive finish.

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. These three marks represent the three types of different rays emitted by radioactive substances. The radiation which deviated slightly towards positively charged plate is a beta rays. And second type of radiation deviated towards negatively charged plate is called alpha rays. The third radiation did not deviate and called ass gamma rays.

g. Certain types of ceramic tiles are fixed on the outer layer of a shuttle because they can withstand high temperatures without decomposing. They are water resistant and electric insulators.

a. Food colours are the substances added to food to increase the acceptability and attractiveness of the food product. For examples: Allura Red AC, Tartrazine.

Harmful effects of artificial food colours:

(i) Food colours added to pickles, jams and sauces contain small quantities of lead and mercury. These can be harmful for those who consume these products on a regular basis.

(ii) Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children who consume foods with added food colours, especially when such food is consumed in excess.

b. (i) Water of crystallisation is the number of water molecules that combine chemically in definite molecular proportion, with the concerned salt in the crystalline state.

(ii)Two correct examples are:

Copper sulphate, chemical formula - CuSO­­₄.5H₂O

Use: It is used as an antiseptic and as an antifungal agent for topical use.

Washing soda, chemical formula - Na₂CO₃.10H₂O

Washing soda is used:

1. In paper, paints and textile industries.

2. In the manufacture of glass, soap, borax and caustic soda.

c. Electrolysis is a redox process. The reaction at the cathode involves reduction of cations as they gain of electrons while the reaction at anode involves oxidation of anions as they loss of electrons to become neutral. There are three methods of electrolysis of sodium chloride:

(i) In the electrolysis of molten NaCl, sodium is deposited at the cathode while chlorine gas is liberated at anode.

(ii) In the electrolysis of aqueous solution of NaCl, Cl₂ gas is liberated at anode and H₂ gas is liberated at cathode.

(iii) In the electrolysis of concentrated sodium chloride sodium hydroxide, hydrogen gas and chlorine gas are formed.

a. Anodizing: It is used for iron surfaces to protect them from rusting. It is used in the manufacturing of anodized utensils like griddles and cookers.

b. Powder coating: It makes painted architectural steel parts resistant to heat damage, cold damage and even corrosion.

Most of metal products designed to be used outdoors are finished using the powder coating method.

c. Radioactive substances

(i) Calcium -47is an important aid to biomedical researchers for studying the cellular functions and bone formation in mammals.

(ii) Chromium -51 is used in research in red blood cell survival studies.

(iii) Cobalt-57 is used as a tracer to diagnose pernicious anemia

(iv) Gallium-67 is used in medical diagnosis.

d. Ceramic: Due to water resistant and an electrical insulator properties it is used in electrical instruments, for coating the interior of a kiln, the outer surfaces of ships and blades of jet engines. It is also are used as superconductors.

a. Artificial dye

(i) Hair fall, damage to hair texture, burning of skin, adverse effect on eyes, etc. are the after effects of dyeing hair.

(ii) A dye named carmine present in lipsticks does not affect lips but causes stomach disorders

b. Artificial food colour:

(i) Food colours added to pickles, jams and sauces contain small quantities of lead and mercury. These can be harmful for those who consume these products on a regular basis.

(ii) Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children who consume foods with added food colours, especially when such food is consumed in excess.

c. Radioactive substances

(i) The radiation coming out from radioactive can damaged the central nervous system.

(ii) Some genetic or hereditary defects are generated by bombardment of radiation on D.N.A in the body.

d. Deodorant

(i) Deodorant causes disorders like headache, asthma, respiratory disorders, heart disease are likely to occur without our knowledge.

(ii) A chemical named aluminium chlorohydrates may cause various skin disorders and also skin cancer.

Bleaching powder(Calcium Oxychloride) - CaOCl₂ Common salt (sodium chloride) - NaCl Baking soda(Sodium Hydrogen Carbonate) - NaHCO₃ Washing soda (Sodium carbonate) - Na₂CO₃

The above picture shows the process of powder coating. In Powder coating method, the particles of the powder are given an electrostatic charge due to which a uniform layer of the powder sticks to the metal surface.

It makes painted architectural steel parts resistant to heat damage, cold damage and even corrosion.

Most of metal products designed to be used outdoors are finished using the powder coating method.