We learned about Metals & Its Reactivity Series.
Sodium (Na) is considered a very reactive metal and it will reacts vigorously when added into water.
Video below shows the “mini explosions” that occurs when a small piece of sodium is added into a large basin of water.
Alternatively, you can check out this specific link to this youtube video.
http://www.youtube.com/watch?v=6xEyik_dQZI
PS: What is product of this reaction? Leave me a comment below this post.