Volcanic molten lava pours out and re-hardens back into the rock again. Chemical change or physical change?

To find the enthalpy of a reaction in the lab, you measured the of the reactants and the change during the reaction.

How is energy related to the change of state represented by the model? atoms gain energy as a solid changes to a liquid. atoms gain energy as a solid changes to a gas. atoms lose energy as a solid changes to a liquid. atoms lose energy as a solid changes to a gas.

If a simple machine aduces the strength of a force, what must be increased? the speed of the input force the work the simple machine performs the size of the simple machine the distance over which the force is applied