Question 1: Define a heating curve and explain what it illustrates about the state of a substance.

Answer: A heating curve shows how the temperature of a substance changes as heat is added, illustrating phase changes and temperature plateaus during melting and boiling.

Question 2: Describe what occurs at a plateau on a heating or cooling curve.

Answer: At a plateau, the substance is undergoing a phase change, where energy is used to change its state rather than its temperature.

Question 3: Explain the difference between sensible heat and latent heat.

Answer: Sensible heat causes a change in temperature without changing the state, while latent heat is used during a phase change to alter the state without changing temperature.

Question 1: A 500 g sample of water is heated from 20°C to 100°C. How much heat energy is required? (Specific heat capacity of water = 4.18 J/g°C)

Answer: Q = mcΔT = 500g × 4.18 J/g°C × (100°C - 20°C) = 500 × 4.18 × 80 = 167,200 J

Question 2: How much energy is needed to convert 200 g of ice at -10°C to water at 0°C? (Specific heat of ice = 2.09 J/g°C, latent heat of fusion = 334 J/g)

Answer: Q = mcΔT + mL = 200g × 2.09 J/g°C × 10°C + 200g × 334 J/g = 200 × 2.09 × 10 + 200 × 334 = 4,180 + 66,800 = 70,980 J

Question 1: List three variables that must be controlled in an experiment measuring the heating curve of water. Also, mention one safety precaution.

Answer: Variables: mass of water, initial temperature, heat source power; Safety precaution: avoid boiling over or splashing hot water.

Question 1: A substance's temperature remains constant at 0°C for a period while heat is continuously supplied. What phase change is occurring, and what does this indicate about the energy being used?

Answer: The substance is melting (or freezing if cooling), and the energy supplied is being used as latent heat for the phase change rather than changing temperature.

Question 1: Describe the changes in energy and temperature that occur when a solid is heated from its melting point to its boiling point, including the concepts of sensible and latent heat. Use appropriate scientific terminology.

Answer: When a solid is heated from its melting point to its boiling point, it first absorbs sensible heat, causing its temperature to rise until it reaches the melting point. At this stage, the temperature remains constant during melting as latent heat is absorbed to change the solid into a liquid. Once fully melted, further heating causes the liquid's temperature to increase (sensible heat) until it reaches the boiling point. During boiling, latent heat is again absorbed to convert the liquid into a gas at constant temperature. Throughout this process, energy is used both to increase temperature and to facilitate phase transitions.

Question 1: Provide an example of a practical application where understanding phase changes and heating curves is essential, and briefly describe its significance.

Answer: Refrigeration and air conditioning systems rely on phase changes (e.g., evaporation and condensation) to transfer heat efficiently, which is based on principles from heating/cooling curves.