Have you ever accidentally let go of a helium balloon and watched it float away into the sky? In this episode of SciShow Kids, Jessi and her robot rat friend Squeaks explore the science behind that very moment. They explain exactly why helium balloons float while other objects don't, using a simple and effective analogy involving a spoon in a bowl of water to demonstrate the concept of density and buoyancy in a way young learners can grasp. The video takes students on a journey upwards through the atmosphere, investigating how conditions change as altitude increases. It covers key physical science concepts including air pressure (described as air spreading out), the properties of gases like helium, and atmospheric temperature changes. Viewers learn about the material science of rubber, seeing how it stretches when gas expands and becomes brittle when exposed to freezing temperatures at high altitudes. Beyond the physics, the video provides a crucial lesson in environmental stewardship. It explains the eventual fate of all balloons—popping or shattering and falling back to Earth—and the specific dangers this litter poses to wildlife who might mistake it for food. This combination of physics, earth science, and environmental responsibility makes it an excellent resource for discussing properties of matter, the atmosphere, and human impact on the environment.