The papers in a car on a scorching hot day are unlikely to catch fire due to several reasons:
Ignition Temperature: Paper has an ignition temperature, which is the minimum temperature required to ignite it. The ignition temperature of paper is generally around 451°F (233°C). While the inside of a car can become extremely hot on a hot day, it's unlikely to reach temperatures high enough to surpass the ignition temperature of paper.
Heat Dissipation: Heat is transferred from the environment to the papers in the car through conduction and convection. However, paper is a good insulator and does not conduct heat very well. This means that even if the external temperature is high, the heat transfer to the papers may be relatively slow, allowing them to stay below the ignition temperature.
Air Circulation: In a car, the air is not completely stagnant. Natural air circulation occurs through small openings or gaps in the windows and doors, preventing the temperature inside from reaching extreme levels. The movement of air helps dissipate heat and prevents localized hot spots that could potentially ignite the papers.
It's important to note that while the papers may not catch fire in this scenario, prolonged exposure to high temperatures can cause the papers to become brittle, discolored, or degrade over time. Additionally, if there are other flammable materials or sources of ignition present in the car, the risk of fire may increase. Therefore, it's generally advisable to avoid leaving flammable materials unattended in hot environments for extended periods.