Science Buddies: https://www.sciencebuddies.org/science-fair-projects/science-projects
Tips from YouTuber Mark Rober (former NASA engineer): https://www.youtube.com/watch?v=UBuH1b0Dqm0
Search the internet and add "for kids" - there are lots of simplified videos or diagrams. Also, try your local library for kids science magazines or Amazon and Costco for kid's science books. There are MANY written for the elementary age group. If you can make a hands-on example that kids can relate to, they'll love it!
NASA Kids’ Club provides a plethora of space focused games, videos, images and activities to introduce and help kids learn about the world of space.
BrainPOP offers educational animated videos and lessons covering different science topics. Each featured science topic comes with illustrative videos, quizzes, and accompanying activities.
Another excellent source of educational video content to help kids learn about different science topics. The site also provides interactive games and links to mobile science apps for kids.
4) Science Kids
As its name indicates, Science for Kids is a website that features a treasure trove of educational science materials. These include online games, experiments, lesson plans, quizzes, science projects, free activities and many more.
Nat Geo Kids enables science lovers to explore the world of science through a collection of apps, games, magazines, toys, videos, and many other materials.