In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: In the fifth day , the platform was elevated above the water surface in another position to evaluate the function of motor , motivational and visual systems .
### Output Text:
In the fifth day , the platform was elevated above the water surface in another position to evaluate the function of motor , motivational and visual systems . 