Cool air at 20.0ºC is forced into a hot-air balloon with an operating volume of 2500 m^3 using a fan. If the air in the hot-air balloon reaches a maximum operating temperature of 120ºC, what volume of air at 20.0ºC must be forced into the balloon to fill the balloon to its operating volume of 2500 m^3 ?

                     1864.11 m³  

Explanation:

             Let's suppose the gas is acting ideally, then according to Charles's Law, "The volume of a fixed mass of gas at constant pressure is directly proportional to the absolute temperature". Mathematically for initial and final states the relation is as follow,

                                                V₁ / T₁  =  V₂ / T₂

Data Given;

                  V₁  =  ??

                  T₁  =  20 °C  =  293.15 K

                  V₂  =  2500 m³

                  T₂  =  120 °C  =  393.15 K

Solving equation for V₁,

                         V₁  =  V₂ T₁ / T₂

Putting values,

                         V₁  =  (2500 m³ × 293.15 K) ÷ 393.15 K

                         V₁  =  1864.11 m³  

Result:

           When 1864.11 m³ volume of gas at 20 °C is allowed to enter a balloon at 120 °C, then the volume will increase to 2500 m³.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.