The only sure evidence for a chemical reaction is changes in properties the formation of a gas a color change the production of one or more new substances

for step 7 table c on the lab "newtons law of action"   the average time it took the car to travel .25 meters   was 1.92 seconds.

the average time it took the car to travel 0.50 meters was 2.61 seconds

hope this : )

colorless gas, exhibiting a blue glow when placed in an electric field

b) solid

its a type of rock