Which two forms of heat transfer work together to heat water in a plastic bottle

The two forms of heat transfer that work together to heat water in a plastic bottle are conduction and convection.

Heat is transferred through solid materials by a process known as conduction.

In liquids, heat is transferred by convectional currents.

For water in a plastic bottle, heat will first have to travel through the solid plastic bottle by conduction before heating the water inside the bottle by convection.

More on heat transfers can be found here: link

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%