A crayon melting in the sun is it chemical or physical change

Initially, the balloon had 3.0 liters of gas at a pressure of 400 kpa and was at a temperature of 294 k. if the balloon is cooled to 277 k and its volume decreased to 1 l, what will the new pressure in the balloon be?

Brainliesttt me asap! the below reaction can be categorized as more than one type of reaction. which reactions are these, and what are the types of reactions?

Although respiratory organs vary across different organisms, they all contain respiratory surfaces that have a large surface area and are extremely thin. explain why having an extremely thin respiratory surface with a large surface area is advantageous for the process of gas exchange