This is an interesting video that describes some problems with the aquatic food web that contains certain types of trout.

This is an interesting educational video created for the younger students.  It is an animation and song that describes the sun and the eight planets.  It does skip poor old Pluto, which I refuse to believe is no longer is a planet.
 

Here is a very well done elementary educational video discussing the importance of soil.  The University of New Mexico created it. They use vocabulary that is easy to understand.  The video will discusses what is found in soil and how it is important to humans and animals.

This video would be a great one to use if you are going to introduce the food web and predator/prey relationships.  It has some great footage of animals chasing each other around.

Discusses how scientists go through the Scientific Method and Processes to experiment ideas, thoughts, notions and observations.   Great video.
 

This video explores why some people get allergies more often then others. What are allergies anyway? Did you know that people with good hygiene are more likely to form allergies or that having a pet as an infant might actually help you avoid getting allergies?

TEDEd created this video, which is an animation about how a cell is attacked by a virus.  It is very detailed and uses language that is easy to understand.  The video will go through many parts of the cell and demonstrates the processes of both the cell and the virus. 
 

Veritasium demonstrates a PyroBoard.  A PyroBoard is a flame that is bounced around by sound waves.  Through the experiment you can actually see and hear how the sound waves change.
 

Veritasium does a good job following the scientific method in order to find out what a candle flame is actually made out of.  Your students will get to see some experiments that will show the answer to the question.
 

This video was created and sung on the show Happy Days.  The tune is catchy and is sung about the process the heart goes through as it pumps blood.  Circulatory System.