Xiaojun took a bus from Bijie to Guiyang to take the piano grade exam in winter vacation. On the way, Xiaojun observed many phenomena related to physics. Because he hasn't studied physics,

(1) Inertia refers to the property that an object stays at rest or moves in a straight line at a constant speed. Because of inertia, Xiaojun still has to maintain his original state of motion, so when the car starts, Xiaojun falls backwards, and when he leaves Bijie Station, the car turns right and Xiaojun turns left.

(2) The water vapor in the car is liquefied into small water droplets when it is cold, and water mist appears on the window glass.

(3) According to the law of energy conversion and conservation of mechanical energy, when a small army goes downhill, its height becomes smaller, but its gravity remains unchanged, so the potential energy of gravity is converted into kinetic energy, so the car is getting faster and faster.

(4) Non-renewable resources refer to material resources that cannot be naturally formed or produced for a long time (millions of years) after being exploited and utilized by human beings once. It includes all kinds of metallic minerals, nonmetallic minerals, rocks, solid fuels (coal, stone coal, peat), liquid fuels (petroleum) and gas fuels (natural gas) in nature, so coal is non-renewable.

(5) A boat floating on the lake is pushed upward by water, which is called buoyancy.

(6) According to the principle that water evaporates and absorbs heat, adding water can cool the body.

Therefore, the answer is: (1) left; Objects have inertia; (2) liquefaction; (3) When the car goes downhill, the gravitational potential energy is converted into kinetic energy, so the speed is getting faster and faster; (4) non-renewable; (5) buoyancy; (6) Use water to absorb heat to cool the body.