Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Question: Water molecules are polar, so they form what type of bonds? Answer: hydrogen
Water molecules are polar, so they form hydrogen bonds. This gives water unique properties, such as a relatively high boiling point, high specific heat, cohesion, adhesion and density.

Question: Matter can exist either as a pure substance or as a combination of what? Answer: different substances
The properties of matter, both physical and chemical, depend on the substances that matter is made of. Matter can exist either as a pure substance or as a combination of different substances.

Question: Burning gas to run our cars is an example of how human activity is contributing to what global event? Answer: climate change
Flickr:futureatlas. com (http://futureatlas. com/blog/). Human activities like burning gasoline in cars are contributing to a global change in our climate . CC BY 2.0.