Answers: 1. A thermal is convection current. It can occur on clear day, when energy from the sun warms the land and the air near it. The warmer air rises (expands) and becomes less dense, as the warm air expands it rises and is replaced by cooler, dense air. 2. Thermals help birds glide in the air for hours, searching for prey. As the warm air rises, the birds can ride it higher by gliding in circles within the thermals. 3. The expression “hot air rises” means that when air is heated, the particles gain energy, move more quickly, and spread out. This air is less dense then the surrounding air, so it rises. 4. Thermals are most likely to be set up in the summer because light (energy) from the sun is more direct and heats up the land more quickly than in winter. 5. Thermals are more likely to be set up on sunny day because the sun’s light can more easily heat up the land than on a cloudy day.