If you are asking for 100 or 400 words, some students will still find it hard to think of enough to write.
Does it have to be true? No it doesn’t. The point of this is to develop writing fluency and the ability to ideate quickly. You could tell them that.
This is the time to remind them that in all writing we need to involve our senses:
- What did you see? Details. Don’t say” a dog.” Say “a brown and white combination cocker spaniel and corgi. Low to the ground with floppy ears and a dopey grin.”
- What did you hear?
- Were there any smells?
- Were there any touch sensations – roughness, smooth, prickly, etc.
- What did you say? Someone else say? Is there a character – give that person personality
- Did you come to realize something important?