When the average kinetic energy of the molecules goes up (a rise in temperature), the average speed of the molecules increases. And lower average kinetic energy of the molecules means they have lower speed. However, a change in average kinetic energy is not directly proportional to a change in average speed. 1.
An appreciation means an increase in the value of a currency. It means a currency is worth more in terms of foreign currency.
The state of or the ease with which a currency may be exchanged for a foreign currency. Currency convertibility is vitally important in the foreign exchange market; higher convertibility means that a currency is more liquid and, therefore, less difficult to trade.