Why did early scientists believe that heat was a fluid

The big bang nucleosynthesis theory states that elements were produced in the first few minutes of the big bang while elements have their origins in the interiors of stars, forming much later in the history of the universe.

The solid xy decomposes into gaseous x and y: xy(s) m x(g) + y(g) kp = 4.1 (at 0 °c) if the reaction is carried out in a 22.4 l container, which initial amounts of x and y will result in the formation of solid xy?

Which aqueous solution of ki freezes at the lowest temperature? 1) 1 mol of ki in 500. g of water 2) 2 mol of ki in 500. g of water 3) 1 mol of ki in 1000. g of water 4) 2 mol of ki in 1000. g of water