The diagram below shows the different phase transitions that occur in matter. Three bars are shown labeled Solid, Liquid, and Gas. They are connected by arrows labeled 1 to 6. Arrow 1 points from liquid to gas; arrow 2 from solid to liquid, arrow 3 from solid to gas, arrow 4 from gas to liquid, arrow 5 from liquid to solid, and arrow 6 from gas to solid. Which best describes the process that arrow 1 represents? Molecules are speeding up during boiling. Molecules are depositing as ice on a surface. Molecules are slowing down during condensing. Molecules are moving from stationary positions.

Molecules are speeding up during boiling

Explanation:

According to the kinetic theory of matter, matter exists in three states; solid, liquid and gas. In the solid state, the molecules of a substance are in fixed positions, the can only vibrate but can not translate. In the liquid state, the molecules acquire a greater degree of freedom and can translate in addition to vibration and rotation. In a gas the molecules are infinitely free and translate at high velocities.

Arrow 1 shows a phase change from liquid to gas. This occurs during boiling. This phase change is possible because the liquid molecules acquire energy in the form of heat supplied during boiling thereby making the molecules of the liquid to speed up their motion and escape the liquid surface as vapour.