Riddle

you are given ten large canvas bags of identical-looking coins. Nine of the bags contain coins that weigh 1 ounce each, and one bag contains coins that weigh 1.1 ounces each. Because of the small difference in weight, you cannot distinguish the 1-ounce coin from the 1.1 ounce coin just by holding them in your hands. And since they look identical in shape and size, they cannot be distinguished that way either. You are given a scale. You can place on the scale as much or as little of the contents of the bags as you wish, and it will display the total weight placed on it. However, you are permitted to use the scale only once. You will get only one chance to figure out which bag has the 1.1 ounce coins.