Internal energy

• Heat transfer occurs when there is a temperature difference between two objects, while work involves moving objects against forces.
• Internal energy can be transferred between objects through heat transfer or work.
• The internal energy is the sum of all energies within an object, including kinetic energy (motion) and potential energy (position).
• The first law of thermodynamics states that the change in internal energy (ΔU) of an object equals the heat transferred to or from it (Q) minus the work done by the object (W).
• Thermal energy is the sum of the random motions of atoms and molecules in a substance.
• The internal energy of an object depends on its composition and the arrangement of atoms within it.
• When an object undergoes a change, such as melting ice into water, the internal energy changes due to the rearrangement of atoms.
• Increasing the pressure of a gas increases the kinetic energy of the molecules, leading to an increase in internal energy.
• Work done on an object increases its internal energy, while work done by an object decreases its internal energy.
• If no work is done, then the change in internal energy equals the amount of heat gained or lost.
• When an object does work, it loses some of its internal energy to do so.
• In a closed system where no mass enters or leaves, Q = W.
• If the net work done on a system is zero, then Q = -ΔU.