Objective: Become familiar with the vocabulary of the unit. 

This worksheet can be a "warm up" to begin the unit of light and sound, since there are many words that children have never heard, and they will naturally ask "What is the meaning of...?" so it is a good way to introduce the vocabulary of the unit, check how much the students know about it and start discussing some of the concepts.

It can also be used at the end of the unit, as a "challenge" or competition, like for example, who can find more than 15 words in less than 7 minutes.