ANS:B - temperature

Temperature is a fundamental physical quantity that quantifies the degree of hotness or coldness of a substance or object. Here's an explanation:

1. Definition: Temperature is a measure of the average kinetic energy of the particles (atoms or molecules) within a substance. In simpler terms, it represents how fast the particles are moving or vibrating.
2. Measurement: Temperature is typically measured using a thermometer, which detects changes in a physical property of a substance that is directly related to its temperature. Common temperature scales include Celsius (°C), Fahrenheit (°F), and Kelvin (K).
3. Kinetic Theory of Gases: According to the kinetic theory of gases, temperature is directly proportional to the average kinetic energy of gas molecules. In a gas, higher temperature corresponds to higher average kinetic energy, resulting in faster molecular motion and increased collisions between particles.
4. Thermal Equilibrium: When two objects at different temperatures are brought into contact with each other, heat transfer occurs until thermal equilibrium is reached. Thermal equilibrium is the state where both objects have the same temperature, indicating that there is no net heat transfer between them.
5. Effect on Matter: Temperature affects the physical and chemical properties of matter. For example:
   • Changes in temperature can cause substances to expand or contract, leading to phenomena such as thermal expansion or contraction.
   • Temperature influences the phase transitions of matter (e.g., melting, freezing, boiling, condensation, and sublimation).
   • Chemical reaction rates generally increase with temperature due to the higher kinetic energy of reacting molecules.
6. Temperature Scales:
   • Celsius (°C): The Celsius scale is based on the freezing (0°C) and boiling points (100°C) of water at standard atmospheric pressure.
   • Fahrenheit (°F): The Fahrenheit scale is commonly used in the United States and is based on a scale where 32°F represents the freezing point of water and 212°F represents its boiling point.
   • Kelvin (K): The Kelvin scale is an absolute temperature scale with zero Kelvin (0 K) representing absolute zero, the lowest possible temperature where all molecular motion ceases. The Kelvin scale is used in scientific applications and is related to the Celsius scale by the equation: K = °C + 273.15.

In summary, temperature is a measure of the average kinetic energy of particles within a substance, influencing their behavior and properties. It is a crucial parameter in physics, chemistry, engineering, and everyday life, governing phenomena such as heat transfer, phase transitions, and chemical reactions.