Answer:
Explanation: A chemical change is a reaction in which chemical composition of the substance changes. Some bonds are broken and some new bonds are formed.
The reactants are written in terms of their chemical formula on the left hand side and the products are written in terms of their chemical formula on right hand side with a arrow in between. The chemical symbols are followed by their physical states such as (l) for liquid, (s) for solid, (g) for gas and (aq) for aqueous.
Thus the only reaction producing a gas is 
Answer - Ozone layer helps keep the harmful ultra violet rays hitting and keeping the atmospheric pressure in.
Reasoning - Without the ozone layer the whole planet would have a loss of water and especially people burning very easily from the sun. <span />
amount of time the two substances are in contact. area in contact between the two substances. specific heat of the material that makes up the substances. the density of the two substances in contact.
Well, if you are moving forward in a direction, then your velocity is your speed with the direction you are moving in. To calculate velocity, you divide your distance traveled by the time it took to travel that distance and you add your direction to it.
So to conclude, 300/100= 3 m/s South
<span>Boyles law states that the volume of a gas is proportional to the moles of the gas when pressure and temperature are kept constant. </span>