What is Carbon dioxide?
[[File:Carbon-dioxide.svg|thumb|[[Stuctural formula]] of carbon dioxide. C is [[carbon]] and O is [[oxygen]]. The double lines represent the double [[chemical bond]] between the [[atom]]s.]] [[File:Carbon-dioxide-3D-vdW.png|thumb|A picture to show simply how the atoms may fill space. The black is carbon and the red is oxygen.]] '''Carbon dioxide''' (CO<sub>2</sub>) is a [[chemical compound]] and is acidic. It is a [[gas]] at [[room temperature]]. It is made of one [[carbon]] and two [[oxygen]] [[atom]]s. People and most animals release carbon dioxide when they breathe out. Also, every time something organic is burnt (or a [[fire]] is made), it makes carbon dioxide. [[Plant]]s use carbon dioxide to make [[food]]. This process is called [[photosynthesis]].<ref>{{cite book|first=Ann|last=Fullick|title=Edexcel IGCSE Biology Revision Guide|url=https://archive.org/details/edexceligcsebiol0000full|publisher=Pearson Education|date=2011|isbn=9780435046767|page=40}}</ref> The properties of carbon dioxide were studied by the [[Scots|Scottish]] scientist [[Joseph Black]] in the 1750s. Carbon dioxide is a [[greenhouse gas]].<ref>{{cite book|first=Steve|last=Woolley|title=Edexcel IGCSE Physics Revision Guide|url=https://archive.org/details/edexceligcsephys0000wool|publisher=Pearson Education|date=2011|isbn=9780435046736|page=[https://archive.org/details/edexceligcsephys0000wool/page/59 59]}}</ref> Greenhouse gases trap [[Thermal energy|heat energy]]. Greenhouse gases change the [[climate]] and [[weather]] on our [[planet]], [[Earth]]. This is called [[climate change]]. Greenhouse gases are a cause of [[global warming]], the rise of Earth surface [[temperature]]. Its concentration in Earth's atmosphere since late in the [[Precambrian]] was regulated by [[photosynthetic]] organisms and geological phenomena (mainly volcanos). == Biological role == Carbon dioxide is an end product in organisms that obtain energy from breaking down sugars, fats and [[amino acid]]s with [[oxygen]] as part of their [[metabolism]]. This is a proce