Predict the properties of the element francium related to its melting point, density and softness.

predict how francium would react with water and write a balanced equations for the reaction

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.