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 second method is the value of Treasury notes. They can be converted easily into dollars through the secondary market for Treasuries. When the demand for Treasuries is high, the value of all money in America rises. The third way the dollar's value is measured is by foreign exchange reserves.