7th Grade Science Topic 3: Energy Transfers, Transformations, and Conservation

Practice flashcards covering definitions, energy forms, energy transformations, conservation laws, and heat transfer mechanisms from the 7th Grade Science Topic 3 Study Guide.

Energy

The ability to do work or cause change, measured in Joules ($J$).

Potential Energy (PE)

Stored energy based on position or condition.

Gravitational Potential Energy

Stored energy that depends on height and weight (or mass), exemplified by a roller coaster at the top of a hill.

Chemical Potential Energy

Energy stored in chemical bonds, such as in food, gasoline, and batteries.

Kinetic Energy (KE)

The energy of motion, which increases with greater mass and faster speed (such as a rolling bowling ball).

Mechanical Energy

The form of energy consisting of motion plus position.

Thermal Energy

The total particle kinetic energy of an object or system.

Electrical Energy

The form of energy associated with moving charges.

Radiant Energy

The form of energy transmitted by electromagnetic waves.

Sound Energy

The form of energy produced by vibrating particles.

Nuclear Energy

Energy stored in an atom's nucleus.

Energy Transformation

The process of energy changing from one form to another.

Flashlight Energy Chain

Chemical energy in the battery transforms to electrical energy in the circuit, which transforms to radiant energy (light) and thermal energy (waste heat).

Solar Panel to Light Bulb Energy Chain

Radiant energy from the Sun transforms to electrical energy in the panel, which transforms to radiant energy from the bulb plus thermal energy.

Hydroelectric Power Energy Chain

Gravitational potential energy of water in a reservoir transforms to kinetic energy of falling water and a turning turbine, which transforms to electrical energy in a generator.

Law of Conservation of Energy

The fundamental principle stating that energy cannot be created or destroyed; it can only transform or transfer, meaning the total energy in a closed system remains constant.

Apparent 'Lost' Energy

Energy that seems to disappear when devices operate, but has actually transformed into non-useful forms like thermal energy (due to friction or resistance) and sound.

System Boundaries

The defined limits of an investigation; ignoring heat and sound escaping across these boundaries into surrounding air causes energy to mistakenly appear to disappear.

Golden Rule of Heat Flow

The rule that thermal energy always flows spontaneously from warmer objects (high temperature) to cooler objects (low temperature).

Thermal Equilibrium

The state that occurs when two objects reach the same temperature.

Conduction

Heat transfer through direct contact, which is most effective in solids.

Convection

Heat transfer in fluids (liquids and gases) where warm fluid expands, becomes less dense, and rises, while cooler, denser fluid sinks.

Radiation

Heat transfer by electromagnetic waves that can travel through space without requiring matter.