Which of the following compounds would most likely be the reactants in a combustion reaction? sulfuric acid and water
oxygen and hydrocarbon
oxygen and carbon dioxide
carbon dioxide and hydrocarbon

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

4d^55s^1 ( third choice)

intermolecular forces are the forces between molecules or particles.

there are two kinds of van der waals forces: weak london dispersion forces and stronger dipole-dipole forces.

in molecule of water there are dipole-dipole forces between negatively charged oxygen from one molecule of water and positively charger hydrogen of another molecule of water.

hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (h), covalently bound to a highly electronegative atom such as flourine (f), oxygen (o) and nitrogen (n) atoms.