Solution-Class 9-Science-Chapter-14-Substances in Common Use-Maharashtra Board

1. The number of molecules of water of crystallization in washing soda is 10.

2. The chemical name of baking soda is sodium bicarbonate.

3. Iodine I-123is used in treatment of hyperthyroidism.

4. The chemical name of Teflon is polytetra fluoroethene.

Elements with a high atomic number such as uranium, thorium, radium have a property of spontaneously emitting invisible, high penetrating and high energy radiation. This property is called radioactivity.

Nucleus of certain elements such as uranium, thorium, radium etc. have a property of spontaneously emitting invisible, highly penetrating and high energy radiation. The nucleus is said to be unstable, when nucleus of radioactive substances undergoes spontaneous decay by self-emission of either alpha (α), beta (β), or gamma (γ) radiations to form a more stable nucleus.

• Colours used in pickles, jam and sauces contain lead and mercury in small quantities. Regular consumption of these products can be dangerous to health.
• Tetrazene, sunset yellow these are artificial food colours used extensively. Excess consumption of these artificial food colours can be detrimental to health.
• These artificial food colours cause diseases like ADHD in small children, allergies, disorders of the nervous system, cancer, etc.

​Radioactivity has various industrial application:

• It is used as a fuel in nuclear reactors to generate power.
• Internal cracks and voids in cast iron articles can be detected with the help of gamma rays
• It is used in controlling the thickness of paper, plastic and metal sheets during their manufacturing.
• It is used in the manufacturing of luminescent paints and objects which show radioluminance. For example, substances such as radium, promethium etc. are used to make objects which glow in the dark like hands of clock. Similarly, krypton-85 is used in high intensity discharge lamps.
• Radioactive substances are used in ceramics, utensils, plates etc. to obtain luminous colours.

Teflon has the following properties:

• It is not influenced by the atmosphere and chemical substances
• both water and oil do not stick to the Teflon coated articles
• it has a high melting point i.e. 327⁰ C which means there is no effect of high temperatures on it
• Teflon coated articles are easy to clean

• We should use natural colours made from plants for celebrating an echo friendly Rang Panchami.
• These natural colours can be made from natural ingredients like beet root, flowers of flame of forest, spinach, flame tree (gulmohar) etc. These are natural colours which do not pose any threat to our health or the environment.
• The synthetic/artificial colours which we use are a serious threat to our health as they can lead to problems like blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores etc.

Teflon is a substance which is inert to chemicals, stable at higher temperatures, easy to clean and nonstick. All these properties make it an ideal substance for coating.

Chlorine is the main constituent of bleaching powder. When exposed to air, bleaching powder reacts with carbon dioxide in air to produce calcium carbonate and chlorine. Thus, it smells of chlorine.

The hardness of hard water is due to the presence of chlorides and sulphates of calcium and magnesium. When washing soda (Na₂CO₃. 10H₂O) is added to the hard water, Na₂CO₃ reacts with the chlorides and sulphates of calcium and magnesium and converts them to insoluble carbonate salts. This changes the hard water into soft water and thus makes it suitable for use.

MgCl2 (aq)+ Na2CO3 (s) ® MgCO3(s) + 2 NaCl (s)

When soap is added to hard water, the displacement of sodium takes place and calcium, magnesium salts of fatty acid are formed. Since these salts are insoluble in water, they form a precipitate, therefore, soap forms a precipitate in the hard water and does not foam.

• A method of applying a layer harder than paint on the surface of an iron object to prevent rusting is called powder coating.
• In this method, a polymer resin, a pigment and some other ingredients are melt mixed, cooled and ground into a homogeneous powder.
• This powder is sprayed on the polished metal surface by electrostatic spray deposition (ESD).
• Now, the particles are given an electrostatic charge due to which a uniform layer of powder sticks to the metal surface.
• Then the object is heated in the oven along with the coating.
• A chemical reaction takes place in the layer, resulting in the formation of long cross-linked polymeric chains.
• This powder coating is highly durable, hard and attractive.

Anodizing is done by electrolysis. In the electrolytic cell, dilute acid is taken and the aluminium article is dipped in it as anode. When an electric current is passed hydrogen gas is liberated at the cathode and oxygen gas is liberated at the anode. A reaction with oxygen takes place and a layer of hydrated aluminium oxide is formed on the anode. This layer can be made attractive by adding colour in the cell during electrolysis.

When the radiation coming out from certain radioactive substance is passed through an electric field, marks of three distinct spot are found on the photographic plate placed in its path. These three marks represent the three kind of rays which are emitted by the radioactive substances. One type of radiation deviated slightly towards the negatively charged plate and were called alpha rays. The second type of radiation deviated substantially towards the positively charged plate and was called the beta rays. The third type of radiation did not deviate at all and was called the gamma rays.

A certain type of ceramic tiles are fixed on the outer layer of a space shuttle. They are made from alumina (Al₂O₃), zirconia (ZrO₂), silica (SiO₂) and a few oxides like (SiC), (B₄C). These tiles require a temperature of 1600 °C to 1800 °C and an oxygen free atmosphere for firing. These tiles are heat resistant, water resistant and are electrical insulators. Some types of ceramics are also used as superconductors.

Artificial food colours used for :

• For Red colour : Ponceau 4 R, carmoisine and erythrosine.
• For yellow colour : tetrazene and sunset yellow FCF.
• For blue colour : Indigo carmine and Brilliant blue FCF.
• For green colour : Fast green FCF.

Excessive consumption of these colours can be detrimental to health. These artificial food colours cause diseases like ADHD in small children, allergies, disorders of the nervous system, cancer, etc.

Water of crystallization is a fixed number of water molecules present in the crystal structure.

Substances in our daily use which contain salt with water of crystallization :

1. Alum (Potash alum — (K₂SO₄.Al₂(SO₄)_3.24H₂O) :

• Alum and burnt alum is used in medicines.
• In the paper industry, alum is used to give shine to the paper.
• Alum is used to stop bleeding from Wound.
• Alum is used in the process of purification of water.

2. Bor (Na₂B₄O₇.1OH₂O) :

• Borax is used in the cosmetic industry to make lotions, shampoos and cold creams.
• It is used to remove the stain on clothes in a laundry;
• In the laboratory with the help of borax bead test, basic elements from the coloured salts are determined.

3. Epsom salt (Magnesium sulphate MgSO₄.7H₂O):

• Epsom salt is used in the manufacture of fertilizers and also to enhance the green colour of plants and vegetables.
• It is used in the manufacture of purgative medicines.
• It is used as body scrub.
• It is added in bath water (salt bath) to relieve muscle pain.

4. Barium chloride (BaCl₂.2H₂O) :

• It is used in the purification of brine solution. (saturated sodium chloride solution).
• It is used in the waste water management.
• It is used in the paper industry and also used in the dye industry, ceramics, oil purification and pesticides.

5. Sodium sulphate (Glauber’s salt Na₂SO₄.10H₂O) :

• It is used in the preparation of detergents.
• It is used to make paper pulp in paper industry and also used in the dye in the dye industry.
• It is used to make mild purgatives.

6. Blue vitriol (CuSO₄.5H₂O) :

• It is used in the blood test to diagnose anaemia.
• Blue vitriol and slaked lime is used in the Bordeaux mixture, which is used as a fungicide on fruits.

(1) When an electric current is passed through very dilute solution of sodium chloride (dissolve 2 g salt in 500 ml pure water) it is electrolysed and hydrogen gas is liberated at the cathode and oxygen gas is liberated at the anode.

(2) When an electric current is passed through a saturated solution of sodium chloride it is electrolysed and hydrogen gas is liberated at the cathode and chlorine gas is liberated at the anode.

(3) When salt is heated to a high temperature (about 800 0C), it melts. This is called the fused state of the salt. When fused sodium chloride salt is electrolysed, chlorine gas is liberated at the anode and liquid sodium is deposited at the cathode

Anodizing :

• Anodizied cooking utensils like griddles cookers and pans are nonstick, scratch resistant and can be easily cleaned.
• Anodized utensils are heat resistant, nonpoisonous, long lasting. Food cooks faster in these vessels.

• It is used for iron surfaces to protect them from rusting.

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. 
• Domestic appliances and windows are powder coated. They are long lasting and look attractive.

Radioactive substances :

• It is used as a fuel in nuclear reactors to generate power.
• It is used in controlling the thickness of paper, plastic and metal sheets during their manufacturing.
• It is used in the manufacturing of luminescent paints and objects which show radioluminance. For example, substances such as radium, promethium etc. are used to make objects which glow in the dark like hands of clock. Similarly, krypton-85 is used in high intensity discharge lamps.
• Radioactive substances are used in ceramics, utensils, plates etc. to obtain luminous colours.
• In medical science, it can be used for detection of cancer, treatment of hyperthyroidism and bone cancer.
• In agricultural field they are used in food preservation, prevention of sprouting in onions and potatoes etc.

Ceramics :

• They are used in making roofing tiles, construction bricks, pottery, terracotta etc.
• Special type of ceramics are used in outer surfaces of ships and blades of jet engines.
• They are also used on the outer surfaces of space shuttles.

• Use of dye for dyeing hair can have adverse effects like hair fall, damage to hair texture, burning of skin.
• The dyes used for dyeing hair have an equally adverse effect on eyes, etc.
• Dyes present in lipsticks are a cause of stomach disorders.

• Colours used in pickles, jam and sauces contain lead and mercury in small quantities. Regular consumption of these products can be dangerous to health.
• Tetrazene, sunset yellow these are artificial food colours used extensively. Excess consumption of these artificial food colours can be detrimental to health.
• These artificial food colours cause diseases like ADHD in small children, allergies, disorders of the nervous system, cancer, etc.

• Radioactive substances affect the central nervous system.
• Exposure to radioactive radiations for long periods can lead to hereditary defects.
• They can penetrate the skin, and causes diseases like skin cancer, leukemia.

• It contains aluminium – zirconium compounds which are the most harmful chemicals in the deodorant. They can result in the development of disorders like headache, asthma, respiratory disorders, heart disease without our knowledge.
• Presence of aluminium chlorohydrates may also result in the development of various skin disorders and skin cancer.

• The chemical formula of bleaching Powder is CaOCl₂.
• The chemical formula of common salt is NaCl
• The chemical formula of baking soda is NaHCO₃
• The chemical formula of washing Soda is Na₂CO₃.10H₂O.

The above picture shows the process of powder coating. 

• A polymer resin, a pigment and some more ingredients are melted, mixed, cooled and ground into a uniform powder.
• This powder is sprayed on the polished metal surface by electrostatic spray deposition (a method in which the particles of powder are given an electric charge) that makes a uniform coating on the substance.
• Once completely coated, the object is then heated, which results in the formation of long cross-linked polymeric chains.
• This coating is highly durable, hard and attractive.
• It can be done on plastic and medium density fibre board as well.