Question 1: Define the term 'vaporization' and explain the difference between boiling and evaporation.

Answer: Vaporization is the process of a liquid turning into a gas. Boiling occurs throughout the liquid at a specific temperature, called the boiling point, while evaporation occurs at the surface and can happen at temperatures below boiling point.

Question 2: Describe what happens at the molecular level during melting.

Answer: During melting, the molecules in a solid gain energy, vibrate more vigorously, and overcome their fixed positions, transitioning into a liquid state.

Question 3: Explain the concept of latent heat in the context of phase changes.

Answer: Latent heat is the energy absorbed or released during a phase change without changing temperature, used to break or form intermolecular bonds.

Question 1: Calculate the amount of heat energy required to convert 250 grams of ice at -10°C to water at 0°C. (Specific heat of ice = 2.1 J/g°C, latent heat of fusion = 334 J/g)

Answer: Q = (mass × specific heat × temperature change) + (mass × latent heat of fusion) = (250 g × 2.1 J/g°C × 10°C) + (250 g × 334 J/g) = 5250 J + 83500 J = 88750 J

Question 1: Identify three variables that could affect the rate of evaporation in an industrial cooling process and suggest safety precautions when handling hot liquids.

Answer: Variables include temperature, surface area, and air flow. Safety precautions include wearing heat-resistant gloves, eye protection, and working in a well-ventilated area.

Question 1: A metal alloy is subjected to intense heating, causing some components to melt while others remain solid. Explain what factors influence selective melting and how this impacts manufacturing.

Answer: Factors include differences in melting points of components, heat distribution uniformity, and cooling rates. Selective melting allows precise shaping and material properties but requires careful control to prevent unwanted phase changes.

Question 1: Describe the process and energy changes involved when water boils at 100°C under atmospheric pressure. Include the role of latent heat and molecular behavior.

Answer: When water reaches 100°C at atmospheric pressure, it undergoes vaporization. Molecules gain enough energy to overcome intermolecular forces, transitioning into vapor. The process absorbs latent heat of vaporization, which is used to break bonds without increasing temperature, and the vapor molecules move freely, forming steam.

Question 1: In the design of a refrigeration system, how does understanding phase changes improve efficiency and safety? Provide specific examples.

Answer: Understanding phase changes allows engineers to select appropriate refrigerants with suitable boiling points, optimize heat exchange, and prevent pressure build-up. Proper management of vaporization and condensation enhances efficiency and reduces safety risks like explosions or leaks.