Which class of molecules functions as chemical signals? hormones water carbohydrates proteins

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?

Exit what is the density of an object having a mass of 5.0 g and a volume of 45.0 cm3?

In in , is to a 28.4-g (1-oz)−23.0 °c to −1.0 °c?