It makes sense that a balloon filled with a lightweight gas such as helium would float when surrounded by heavier air. But why does filling a huge balloon with hot air also make it float? This ...

Students will be able to explain that the density of a liquid has to do with how heavy it is for the sample size. Students will also be able to explain that if a liquid is more dense than water, it ...

Note: This video is designed to help the teacher better understand the lesson and is NOT intended to be shown to students. It includes observations and conclusions that students are meant to make on ...

It is tempting to think that some materials are always heavier than other materials. For example, someone might say that metal is heavier than air. But it depends on how much of each material there is ...