Heat causes water molecules to expand

Hey student studies gravity using objects that have the same mass which two objects have the greatest gravitational force acting between them a. 100kg 1.0m 100kg b. 100kg 2.0m 100kg c. 100kg 2.0m 100kg big d. 100kg big 3.0m 100kg big

How many neutrons does element x if it’s atomic number is 28 and its mass number is 87

What does the law of conservation of mass state?