Solar power is expensive, but as demand increases technology improves and costs decrease. In the past, solar power was more expensive or less expensive than it is today?
more expensive

(Question)
This is also called diffusion, and the process is much faster in gases than in liquids, because the particles in gases are further apart. Kate is going to diffuse a liquid and a gas. The liquid is diffused last, because the particles with it are closer together or further apart?
(Answer)
closer together

Ques: Warm air is less dense than cool air, so it rises higher in the troposphere. If Mona heats up the air she is putting into her weather balloon, what will happen to the height that it can rise into the troposphere increase or decrease?
Ans: increase

(Q).
As greenhouse gases increase, changes will be more extreme. John was looking at the climate model data in his office. He saw there were greater changes as the amount of gases were Lower or Higher?
(A).
Higher

Ques:New farm machines were invented. They increased the amount of food that could be produced. With more food, people were healthier and could live longer. A decrease in food will likely lead to shorter or longer lifespans?

Ans:shorter

Ques: The longer the exposure, the more light that the telescope can gather to make the image. Will was using a flashlight. He used a long exposure and a short exposure. Which exposure likely made the stars seem brighter short or long?
Ans:
long