1. Fill in the blanks:
a. The number of molecules of water of crystallization in washing soda is 10.
b. The chemical name of baking soda is Sodium Bicarbonate (NaHCO₃).
c. Radioactive iodine is used in the treatment of hyperthyroidism.
d. The chemical name of Teflon is Polytetrafluoroethylene (PTFE).
2. Match the pairs:
Group A | Group B
- Saturated brine | c. Crystallization of salt
- Fused salt | a. Sodium metal freed
- CaOCl₂ | d. Oxidation of color
- NaHCO₃ | b. Basic salt
3. Write answers to the following:
a. What is meant by radioactivity?
Answer. Radioactivity is the spontaneous emission of high-energy particles or radiation by the nuclei of certain unstable elements, such as uranium, radium, and thorium. This occurs as the nucleus transforms into a more stable state.
b. When is the nucleus said to be unstable?
A nucleus becomes unstable when there is an imbalance in the number of protons and neutrons. This disrupts the binding energy in the nucleus, making it prone to emitting radiation to achieve stability.
c. Which diseases are caused by artificial food colours?
Diseases such as hyperactivity in children, Attention Deficit Hyperactivity Disorder (ADHD), and allergies can be caused by excessive consumption of artificial food colours.
d. Where in the industrial field is radioactivity used?
Radioactivity is used in industries for:
- Radiography: Detecting internal flaws in metal objects using gamma rays.
- Measuring thickness: Monitoring the thickness of materials like paper and metal sheets.
- Sterilization: Using radiation to sterilize medical equipment and products.
e. Write down properties of Teflon.
- Teflon is non-stick and water-resistant.
- It is chemically inert and does not react with most substances.
- Teflon can withstand high temperatures and is heat-resistant.
- It is durable and has a low coefficient of friction.
f. What type of colours will you use to celebrate eco-friendly Rang Panchami? Why?
Eco-friendly natural colours made from plant-based ingredients or organic powders should be used for Rang Panchami. These are safe for the skin, biodegradable, and do not harm the environment or water sources.
g. Why has the use of methods like Teflon coating become more common?
Teflon coating is widely used because it prevents sticking, is heat-resistant, and has a long lifespan. It is popular in cookware, machinery, and various industries due to its ability to reduce wear and tear, improve efficiency, and ensure easy maintenance.
3. Answer the following questions:
a. What is meant by radioactivity?
Radioactivity is the natural process by which elements with a high atomic number (such as uranium, thorium, and radium) emit invisible, highly penetrating, and high-energy radiation. This phenomenon occurs spontaneously, and substances that exhibit this property are called radioactive substances.
b. When is a nucleus is said to be unstable?
A nucleus is considered unstable when there is an imbalance between protons and neutrons. If the number of neutrons or protons is too high, it disrupts the binding energy that holds the nucleus together, making it unstable. This imbalance often leads to radioactive decay, where the nucleus releases energy to become more stable.
c. What health problems are caused by artificial food colors?
Artificial food colors can have harmful effects on human health. One common condition linked to excessive consumption of food containing artificial colors is Attention Deficit Hyperactivity Disorder (ADHD), which primarily affects children. Some studies also suggest that artificial colors may contribute to allergic reactions and other behavioral issues.
d. Where in the industrial field is radioactivity used?
Radioactivity is used in industries for:
- Radiography: Detecting internal flaws in metal objects using gamma rays.
- Measuring thickness: Monitoring the thickness of materials like paper and metal sheets.
- Sterilization: Using radiation to sterilize medical equipment and products.
e. Write down properties of Teflon.
- Teflon is non-stick and water-resistant.
- It is chemically inert and does not react with most substances.
- Teflon can withstand high temperatures and is heat-resistant.
- It is durable and has a low coefficient of friction.
f. What type of colours will you use to celebrate eco-friendly Rang Panchami? Why?
Answer. Eco-friendly natural colours made from plant-based ingredients or organic powders should be used for Rang Panchami. These are safe for the skin, biodegradable, and do not harm the environment or water sources.
g. Why has the use of methods like Teflon coating become more common?
Teflon coating is widely used because it prevents sticking, is heat-resistant, and has a long lifespan. It is popular in cookware, machinery, and various industries because it reduces wear and tear, improves efficiency, and ensures easy maintenance.
4. Give scientific explanation
a. Bleaching powder has the odour of chlorine.
Bleaching powder releases chlorine gas when it comes in contact with moisture in the air. This is why it has a strong smell of chlorine.
b. The hard water of a well becomes soft on adding washing soda to it.
Hard water contains calcium and magnesium salts, which cause hardness. Washing soda (sodium carbonate) reacts with these salts and forms insoluble compounds, which settle down. This removes the hardness and makes the water soft.
c. Soap forms a precipitate in hard water.
Hard water contains calcium and magnesium ions. When soap is used in hard water, these ions react with the soap to form insoluble compounds, called scum or precipitate, which makes the water unfit for cleaning.
d. The particles of powder are given an electric charge while spraying them to form the powder coating.
Answer. In powder coating, the particles are electrically charged (usually negatively) before being sprayed. The object to be coated is given an opposite charge (usually positive). The opposite charges attract the powder particles to the object, ensuring even coating.
e. The aluminium article is used as an anode in the anodizing process.
Answer. In the anodizing process, aluminium is used as the anode because it allows the formation of a protective oxide layer on its surface when an electric current is passed through an electrolyte. This oxide layer makes the aluminum more resistant to corrosion and enhances its durability.
f. When the radiation coming out from a radioactive substance is passed through an electric field, marks are found at three places on the photographic plate placed in its path.
Radioactive substances emit three types of radiation: alpha, beta, and gamma rays.
- Alpha particles are positively charged and are deflected toward the negative side of the electric field.
- Beta particles are negatively charged and are deflected toward the positive side of the electric field.
- Gamma rays are neutral and pass straight without deflection.
- This behavior creates three distinct marks on the photographic plate.
g. A certain type of ceramic tiles are fixed on the outer layer of a space shuttle.
Answer. The outer layer of a space shuttle experiences extremely high temperatures during re-entry into Earth’s atmosphere due to air friction. Ceramic tiles are used because they are heat-resistant, can withstand these high temperatures, and help protect the shuttle from burning or damage.
5. Write answers to the following:
a. Write about artificial food colors, the substances used in them, and their harmful effects.
Artificial food colors are chemical substances used to make food look attractive. Common substances used are tartrazine, sunset yellow, and erythrosine. These colors can cause harmful effects such as allergies, hyperactivity in children, and even long-term health issues like cancer if consumed in large quantities.
b. What is meant by water of crystallization? Give examples of salts with water of crystallization and their uses.
Water of crystallization refers to the fixed number of water molecules chemically bound to a salt in its crystalline form.
Examples:
- Washing soda (Na₂CO₃·10H₂O): Used in cleaning and softening hard water.
- Gypsum (CaSO₄·2H₂O): Used to make plaster of Paris.
- Blue vitriol (CuSO₄·5H₂O): Used as a fungicide.
c. Write briefly about the three methods of electrolysis of sodium chloride.
- Down’s Process: Sodium chloride is melted and electrolyzed to produce sodium metal and chlorine gas.
- Castner-Kellner Process: Brine (saltwater solution) is electrolyzed using mercury electrodes to produce chlorine gas and sodium hydroxide.
- Membrane Cell Process: Brine is electrolyzed in a cell with a membrane, producing chlorine gas, hydrogen gas, and sodium hydroxide.
6. Write the uses:
a. Anodizing:
Used to protect aluminum from corrosion and to make it decorative.
b. Powder coating:
Used for creating a strong, durable finish on metals.
c. Radioactive substances:
Used in medical treatments (e.g., cancer therapy) and power generation.
d. Ceramic:
Used for making tiles, kitchenware, and space shuttle heat shields.
7. Write the harmful effects:
a. Artificial dye: Can cause skin irritation, allergies, and health problems when inhaled or absorbed.
b. Artificial food color: Can cause hyperactivity in children, allergies, and potential long-term health risks.
c. Radioactive substances: Exposure can lead to radiation sickness, cancer, or genetic damage.
d. Deodorant: Overuse may cause skin allergies and harm due to the presence of chemicals like aluminum.
8. Write the chemical formula:
- Bleaching powder: CaOCl₂
- Common salt: NaCl
- Baking soda: NaHCO₃
- Washing soda: Na₂CO₃·10H₂O