Science week is a great time to discuss the importance of science.
Some countries such as India have Science Day, while other celebrate International Science Week.
The idea is for the students to draw a scientist at the start of the lesson... then compare what they thought science was (generally a wild haired, white guy doing crazy stuff in a lab) with what they thought science was at the end of the lesson and hopefully there has been a change of ideas.
This presentation has links to 2 great YouTube videos which explain why science is so important to everyone. I also listed some of key branches of science, with a brief introduction and pictures. The idea is to discuss how science affects our every day life and how in reality, we are all scientists at heart.