In a car engine, burning fuel produces thermal energy, which causes gases to expand, producing kinetic energy
true
false

True

Explanation:

Thermal energy can be described as the energy which arises in atoms due to increase in temperature. It is also known as heat energy. When a fuel burns, the atoms collide with a greater force and get converted into gas. Burning causes the gases to expand and provide energy for movement of the car, Kinetic energy can be described as the energy which is present in the atoms of a moving object. Hence, the statement is true.  

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.