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.
Currencies appreciate against each other for various reasons, including capital inflows and the state of a country's current account. Typically a forex trader trades a currency pair in the hopes of currency appreciation of the base currency against the counter currency.