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.
Synonyms: appreciate, value, prize1, esteem, treasure, cherish. These verbs mean to have a highly favorable opinion of someone or something. Appreciate applies especially to high regard based on critical assessment, comparison, and judgment: As immigrants, they appreciated their newfound freedom. Value implies high regard for the importance or worth of the object: In principle, the modern university values ... the free exchange of ideas (Eloise Salholz).