WAEC Physics 2014 Paper

Concept:The usable temperature range of a liquid-in-glass thermometer depends on the freezing and boiling points of the liquid used inside it.Explanation:A clinical thermometer is designed only for body temperature, covering roughly $35^{\circ}\mathrm{C}$ to $42^{\circ}\mathrm{C}$.Therefore, it cannot measure a temperature as low as $-50^{\circ}\mathrm{C}$.Mercury freezes at about $-39^{\circ}\mathrm{C}$.Below this point, mercury solidifies, so a mercury thermometer cannot measure $-50^{\circ}\mathrm{C}$.Alcohol freezes at approximately $-114^{\circ}\mathrm{C}$ and boils at about $78^{\circ}\mathrm{C}$.Hence, an alcohol-in-glass thermometer can easily measure temperatures from $-50^{\circ}\mathrm{C}$ to $50^{\circ}\mathrm{C}$.So, only the alcohol-in-glass thermometer is suitable for the given range.Answer:C. iii only