Define Chemistry.

Here are the short answers to the questions:

1. Define Chemistry. Chemistry is the scientific study of matter, its properties, how it interacts and changes, and the energy changes that accompany these processes.

2. Define volume and specific gravity.

   • Volume: The amount of three-dimensional space occupied by a substance.
   • Specific Gravity: The ratio of the density of a substance to the density of a reference substance (usually water at $4^\circ\text{C}$). It is a dimensionless quantity.

3. Define cation and anion.

   • Cation: A positively charged ion, formed when an atom loses one or more electrons.
   • Anion: A negatively charged ion, formed when an atom gains one or more electrons.

4. Define formula write names of its types.

   • Formula: A representation of a chemical compound using symbols for the elements and subscripts to indicate the number of atoms of each element.
   • Types: Empirical Formula, Molecular Formula, Structural Formula.

5. Define isotope. Give two examples.

   • Isotope: Atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different mass numbers.
   • Examples: Carbon-12 ($^{12}\text{C}$) and Carbon-14 ($^{14}\text{C}$); Hydrogen-1 ($^{1}\text{H}$) and Hydrogen-2 ($^{2}\text{H}$).

6. Define Octet rule. The Octet Rule states that atoms tend to gain, lose, or share electrons to achieve a full outer electron shell with eight electrons, similar to noble gases, which provides stability.

7. Define viscosity and write its unit.

   • Viscosity: A measure of a fluid's resistance to flow, describing its internal friction.
   • Unit: The SI unit is the pascal-second ($\text{Pa}\cdot\text{s}$).

8. What is chemical name of water. Which oxide is it.

   • Chemical name of water: Dihydrogen monoxide.
   • Type of oxide: It is a neutral oxide.

9. Write formula of sodium zeolite. A common formula for sodium zeolite (Zeolite A) is $\boxed{\text{Na}_{12}\text{Al}_{12}\text{Si}_{12}\text{O}_{48}\cdot 27\text{H}_2\text{O}}$.

10. Write four physical properties of water.

    • 1. It is a colorless, odorless, and tasteless liquid.
    • 2. It has a high boiling point ($100^\circ\text{C}$) and freezing point ($0^\circ\text{C}$).
    • 3. It has a high specific heat capacity.
    • 4. It is a universal solvent.

11. Define sub oxide and per oxide.

    • Suboxide: A compound where the oxygen content is less than expected based on the usual valency of the other element (e.g., $\text{C}_3\text{O}_2$).
    • Peroxide: A compound containing an oxygen-oxygen single bond ($\text{O}-\text{O}$) where each oxygen atom has an oxidation state of -1 (e.g., $\text{H}_2\text{O}_2$).

12. Write four uses of radio isotopes.

    • 1. Medical Diagnosis and Treatment: Used in PET scans and cancer therapy.
    • 2. Carbon Dating: Used to determine the age of ancient artifacts.
    • 3. Industrial Tracers: Used to detect leaks in pipes.
    • 4. Sterilization: Used to sterilize medical equipment and food.

13. Define Alloys. Give two examples.

    • Alloy: A mixture of two or more elements, at least one of which is a metal, typically prepared by melting the components together.
    • Examples: Brass (copper and zinc), Steel (iron and carbon).

14. Describe pitting corrosion. Pitting corrosion is a localized form of corrosion that creates small holes or "pits" in a metal surface. It often occurs in passive metals when their protective layer is locally damaged, leading to concentrated attack.

15. Define Electrode. An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit, such as an electrolyte. In electrochemistry, it is where oxidation or reduction reactions occur.

16. Define Dielectric. Give two examples.

    • Dielectric: An electrical insulator that can be polarized by an applied electric field, causing charges to shift slightly without flowing.
    • Examples: Glass, Plastic.

17. How many electrons are present in valence shell of oxygen. Oxygen has 6 electrons in its valence shell.

18. Write names of types of etching. The main types of etching are Wet Etching and Dry Etching.