Explaining to my students what a Key Signature is and why we need it, and why the F has to be sharp in the Key of G has always been something that I've had trouble explaining without using a lot of visual aids and going through the thought process of why a note would have to stay sharp in order to make the G-Major scale sound correct.
Mostly, I want my students to come away with an understanding of why F is sharp in the key of G without overwhelming them in the details of whole and half steps of the scale, black and white notes on the piano, the intricacies of the Circle of Fifths, etc.
This is a Power Point Presentation that starts with a front-and-back worksheet. the front is follow-and-fill-in that goes along with the Power Point. The back allows them to apply their knowledge of Solfege in the G-Major scale to a eight 1-measure examples.
The Power Point has LOTS of fun animation, some auditory examples to illustrate what G-Major would sound like WITHOUT the F-sharp, and what it sounds like with it, detailed explanations about Solfege, and answered questions that my students ask me a lot as I venture to explain the concept of G-Major without overwhelming them.
I find that the question "What is that hashtag after the Treble Clef?" comes up a lot when we play recorder songs in the Key of G, and that happens starting third grade, so I wrote this to be understood by students at the third grade level, though the information is applicable all the way up to high school if you have students who have never understood what Key Signatures are.
I also wrote out the Power Point kind of like a script, so you could have one student play the Teacher, and one student play the Smiley Student, and have them read through it, or you could have your class read through it together.