Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: You've probably noticed dew on the grass on a summer morning. Why does dew form? Remember that the land heats up and cools down fairly readily. So when night comes, the land cools. Air that was warm and humid in the daytime also cools over night. As the air cools, it can hold less water vapor. Some of the water vapor condenses on the cool surfaces, such as blades of grass. The temperature at which water vapor condenses is called the dew point . If this temperature is below freezing, ice crystals of frost form instead of dew ( Figure below ). The dew point occurs at 100 percent relative humidity. Can you explain why?. Answer: dew point
[EX A]: What is the name of the "point" that refers to the temperature at which water vapor condenses?

[EX Q]: Passage: rates The rates at which reactants are consumed and products are formed during chemical reactions vary greatly. We can identify five factors that affect the rates of chemical reactions: the chemical nature of the reacting substances, the state of subdivision (one large lump versus many small particles) of the reactants, the temperature of the reactants, the concentration of the reactants, and the presence of a catalyst. Answer: catalyst
[EX A]: The presence of what, which acts as a trigger, affects the rate of chemical reaction?

[EX Q]: Passage: Rougher surfaces have more friction between them than smoother surfaces. That's why we put sand on icy sidewalks and roads. The blades of skates are much smoother than the soles of shoes. That's why you can't slide as far across ice with shoes as you can with skates (see Figure below ). The rougher surface of shoes causes more friction and slows you down. Heavier objects also have more friction because they press together with greater force. Did you ever try to push boxes or furniture across the floor? It's harder to overcome friction between heavier objects and the floor than it is between lighter objects and the floor. Answer: friction
[EX A]:
What force is greater on rougher surfaces than smooth surfaces?