How many times should you perform experimental?

Can you recycle cans? A ball falls 5 m and then bounces to a height of 3 m What height is the best reference point for the motion of the ball? What happens when you place marble chips in vinegar? How do mountains affect the amount of precipitation that falls over an area? Why should scientists continue to study cells? In a battery using device the current would flow from the Negitive end through say a led light then find its way to the Positive end of the battery completing the transition? Are the symbols of elements different in different countries? Where do Nodes of Ranvier lie between? What is value of gravity on earth? What are the negative effects of science in your lives? What was coal millions of years ago before it was buried beneath mud and squished? What is a question for vague? One who studies the human mind? What is the Scientific Methods Describe the components of the Scientific Method? Why does flowing bath water sometimes give you an electric shock? What Energy Transformations are in a flashlight? What is the process scientist use to gather information? An automatic response of the body that occurs very rapidly and without conscious control is called? What is the difference between a primary and a secindary source? What happens when a trait shows codominant alleles?