I believe this would be an example of Mary's velocity. We have her speed and direction which is all you need to find velocity.
Oxygen is like a milder form of nitrogen when it comes to its changing forms.
Oxygen becomes a gas when heated above -183 degrees Celsius, and when it is cooled below -183 degrees Celsius, it becomes a liquid.
Just as a bonus, the transition between liquid and solid forms happens when Oxygen is cooled below -218.79 degrees Celsius.
So your answer is "the conversion between the liquid and gaseous states of Oxygen." :)
Answer:
The circulatory system breaks down food and gets / absorbs nutrients. The muscular system works to get nutrients to the rest of the body. The nervous system basically controls the digestive system and sends information to the brain.
I'm pretty sure I'm right, but please correct me if I'm wrong! :)
A chemical change because it doesn't power anything or secrete anything except smoke.