Answer: option B: conduction.
Conduction is the heat transfer that happens between two bodies in direct contact, due to the collision of the molecules, atoms and electrons within the body (microscopical level).
Answer:

Explanation:
We use the kinematics equation to solve this question:

because the ball is dropped
the acceleration is the gravity, negative because it points downwards
initial height
final height
So:


1)
HCl: hydrogen, chloride
3CO2: carbon, oxygen
2Na2SO4:sodium, sulphur, oxygen.
2)
-HCl: 1 hydrogen atom, 1 chlorine atom
-CO2: 1 carbon atom, 2 oxygen atoms
-Na2SO4: 2 sodium atoms, 1 sulphur atom, 4 oxygen atoms.
3)
-HCl: 2 atoms
-3CO2: 9 atoms
-2Na2SO4: 14 atoms.
Answer:
The spring was compressed the following amount:

Explanation:
Use conservation of energy between initial and final state, considering that the surface id frictionless, and there is no loss in thermal energy due to friction. the total initial energy is the potential energy of the compressed spring (by an amount
), and the total final energy is the addition of the kinetic energies of both masses:



Same magnitude (1000N) and opposite direction
you may also answer -1000 N