Mars is red due to red soil rich in iron oxide (rust). Is the oxidation of soil to rust a PHYSICAL or CHEMICAL change How do you know?

i think it is true since you can test the answer and can use observations to complete it.

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.