It is a graph. It shows observations and then you record your results with any of the graph types.
ANSWERS:
1.

⇒ 2KCl +

2.

⇒

3.

⇒

4.

⇒

5.

⇒

I have attached my work for 1-3. I would like to see if you can get 4 and 5 on your own. but, if you are struggling/copnfused please let me know in the comments! :)
Scientists expected that the law of conservation of mass would apply to nuclear fission in terms of the masses of the subatomic particles. In reality, the mass of an atom is not equal to the sum of the masses of the subatomic particles that make it up. This is because of the energy that binds the subatomic particles. This energy has mass and when the bond is broken, the mass of the energy of the bonds is lost resulting to what we now cal, a mass defect.
I'd say it is an element. It is not a compound, it doesn't do things on its own like us. It's an element like fire and water.