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.
Investors will want to exchange their currency for the higher-paying one, and save it in that country's bank to receive the higher interest rate. Second, the money supply created by the country's central bank. If the government prints too much currency, then there's too many dollars, euros or yen chasing too few goods.