6. In the Middle Ages, most scientists believed that the world was made from four simple elements and that almost everything was a mixture.
Which type of pure substance had they not
yet discovered?
Plz help... I need this ASAP

Use the drop-down menus to answer each question. which runner finished the 100 m race in the least amount of time? which runner stopped running for a few seconds during the race? at what distance did anastasia overtake chloe in the race?

Given that 1 mi = 1760 yd, determine what conver- sion factor is appropriate to convert 1849 yd to miles; to convert 2.781 mi to yards.

The human eye contains a molecule called 11-cis-retinal that changes shape when struck with light of sufficient energy. the change in shape triggers a series of events that results in an electrical signal being sent to the brain that results in vision. the minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kj/mol.