Problem: - Above the oven is a tank of water that is sealed - The tank of water begins to boil above the oven - A the water boils steam is created - The steam is denser than air so it needs a place to go - The steam is forced out of the tank and into a piston - The piston moves up - The valve of the piston closes - The valve on the next piston opens - The steam fills the next piston, driving it up, and the other one down - What might be the first step of the process?

A: A fuel is heated in an oven

Problem: - Put the pot over a source of heat - Turn the heat on - Wait for a few minutes - Begin to observe small bubbles in the water - Wait until the water starts to bubble a lot - Wait until you can see steam rising from the water - Turn the heat source off - Take the pot off of the heat source. What might be the first step of the process?

A: Add water to a pot

Problem: - The pollution negatively affects the water quality - The pollution negatively affects the health of plants and animals - The plants and animals have shorter, less healthy lives - The plants and animals do not reproduce very well - The number of plants and animals decreases over time - The quality of water gets worse and worse as there are no plants or animals to clean it - Eventually there is nothing living in the water and it is unusable - What might be the first step of the process?

A: Pollution enters natural water sources such as rivers and lakes

Problem: - The air travels into the windpipe - The windpipe divides the air to the two lungs via the bronchial tubes - The lungs oxygenate the blood in the body - Carbon dioxide is filtered out by every cell in the body - The carbon dioxide is carried back to the lungs via the bloodstream - The carbon dioxide is exhaled. What might be the first step of the process?

A:
Air is taken into the body via the nose or mouth