Question 1: Define thermal energy store and explain how it is transferred between objects.

Answer: A thermal energy store is the energy stored in an object due to the movement of its particles. It is transferred through conduction, convection, or radiation.

Question 2: Describe the mechanism of heat transfer by conduction in solids, providing an example relevant to forensic science.

Answer: Conduction involves direct transfer of kinetic energy between particles in a solid through collisions. For example, heat transfer along a metal weapon during a forensic investigation.

Question 1: A forensic scientist cools a metal knife from 80°C to 30°C. The mass of the knife is 0.5 kg and its specific heat capacity is 385 J/kg°C. Calculate the amount of thermal energy lost by the knife.

Answer: Q = mcΔT; Q = 0.5 kg × 385 J/kg°C × (80°C - 30°C) = 0.5 × 385 × 50 = 9625 Joules

Question 2: A suspect's clothing is found to have absorbed 150 kJ of thermal energy during a fire. If the clothing's mass is 2 kg and its specific heat capacity is 1,000 J/kg°C, by how many degrees Celsius has the temperature of the clothing increased?

Answer: ΔT = Q / (mc) = 150,000 J / (2 kg × 1000 J/kg°C) = 75°C

Question 1: Describe an experiment to measure the specific heat capacity of a material commonly found at a crime scene, including variables to control and safety precautions.

Answer: The experiment involves heating a known mass of the material and measuring the temperature change with a thermometer. Variables to control include initial temperature, heating rate, and environment temperature. Safety precautions include wearing heat-resistant gloves and eye protection, and handling hot equipment carefully.

Question 1: A forensic report states that a piece of fabric absorbed 200 J of thermal energy during a fire. If the fabric's mass is 0.5 kg and its specific heat capacity is 1,200 J/kg°C, estimate the temperature increase of the fabric during the fire. Explain what this information can reveal about the fire's intensity.

Answer: ΔT = Q / (mc) = 200 J / (0.5 kg × 1200 J/kg°C) = 0.33°C. This small increase suggests the fabric absorbed some heat but was not subjected to extremely high temperatures, indicating a relatively moderate fire intensity.

Question 1: Explain how forensic scientists use thermal energy transfer principles to determine the time of a fire.

Answer: They analyze the thermal energy absorbed or transferred by materials, such as fabrics or metals, to estimate the temperature and duration of the fire based on heat transfer models.

Question 2: A piece of metal from a crime scene has a temperature of 55°C, while the environment is at 20°C. If the metal cools at a rate of 2°C per minute through conduction, how long has the metal been at this temperature assuming it initially was at 80°C?

Answer: Time = (80°C - 55°C) / 2°C per minute = 25 / 2 = 12.5 minutes.

Question 1: Discuss how forensic investigators could use thermal imaging technology to locate hotspots at a fire scene and explain the scientific principles involved.

Answer: Thermal imaging detects infrared radiation emitted by objects, allowing investigators to identify areas with higher heat concentrations, which can pinpoint fire origins or ongoing hotspots. This relies on the principle that hotter objects emit more infrared radiation.