Chemical reactions can be represented symbolically using chemical equations. in a chemical equation, reactants appear to the left of the arrow, while products appear to the right. the law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction; rather, the existing atoms are just rearranged. therefore, chemical equations must be balanced—that is, the same number of each kind of atom must be present before and after a chemical reaction.
an unbalanced chemical equation is shown below. balance the equation according to the law of conservation of mass.

If a balloon is taken outside on a very cold day, what will occur?

Which planet do you think would be easiest for humans to colonize some day?

16. a brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800 n on him. the mass of the losing player plus equipment is 90.0 kg, and he is accelerating at 1.20m/s2 size 12{1 "." "20"" m/s" rsup { size 8{2} } } {} backward. (a) what is the force of friction between the losing player’s feet and the grass? (b) what force does the winning player exert on the ground to move forward if his mass plus equipment is 110 kg? (c) draw a sketch of the situation showing the system of interest used to solve each part. for this situation, draw a free-body diagram and write the net force equation.