Here are two ideas:

Plants and Music- You can buy four plants of the same kind at the store. Water and feed them all the same. Grow one without music, grow one with heavy metal music, grow one with classical music, and grow one with pop music. See which one grows the fastest over a two week period. Then say that ___ music makes plants grow faster than without music at all. Tell how this can be used for agriculture.

Cats and Sounds of Birds- (only if you know someone who has a cat) get some recordings of different birds and put a moving stuffed bird in front of it. See if your cat will change behavior when it hears an eagle call compared to a sparrow call.

I wish your friend the best luck! ^^

2. white carnations and food coloring in the water.

3. hurricanes are a apopular topic right now!!! i am sure you can find a lot of projects online!