Q1: A material in which the atoms are arranged regularly in some directions but not in others, is termed as 'mesomorphous material'; an example of which is

ANS:A - lead

Lead is a chemical element with the symbol Pb (from the Latin word "plumbum") and atomic number 82. It belongs to the group 14 (carbon group) of the periodic table. Here are some key points about lead:

1. Physical Properties:
   • Lead is a dense, soft, and malleable metal with a bluish-white color when freshly cut. However, it quickly tarnishes to a dull grayish color when exposed to air.
   • It has a relatively low melting point compared to other metals, melting at 327.5°C (621.5°F).
2. Chemical Properties:
   • Lead is a relatively unreactive metal and does not corrode easily. It forms a protective oxide layer on its surface, which prevents further oxidation.
   • It is resistant to most acids but reacts slowly with hydrochloric acid and sulfuric acid.
3. Applications:
   • Historically, lead has been widely used in various applications due to its low melting point, malleability, and corrosion resistance. Some common uses include:
     • Plumbing: Lead pipes and fittings were commonly used in plumbing systems, although their use has declined due to health concerns.
     • Batteries: Lead-acid batteries are used in vehicles, uninterruptible power supplies (UPS), and other applications.
     • Radiation shielding: Lead is used as a shielding material in medical imaging (X-ray rooms) and nuclear facilities due to its ability to absorb radiation.
     • Solder: Lead-based solders were commonly used in electronics and plumbing, although lead-free alternatives are now preferred in many applications due to health and environmental concerns.
     • Ammunition: Lead is used in bullets and shot for firearms and hunting.
4. Health and Environmental Concerns:
   • Lead is toxic to humans and animals, and exposure to high levels of lead can cause severe health problems, including neurological damage, developmental disorders, and organ damage.
   • Environmental contamination from lead can occur through various pathways, including air pollution, water contamination, and soil contamination. Lead pollution can have significant impacts on ecosystems and human health.