Lesson 49-50. Energy, Thermal Energy, and Temperature

• Energy is the ability to do work and exists in forms like light, sound, electricity, mechanical, thermal, and chemical energy.
• Energy can be converted from one form to another, as seen in a flashlight, where chemical energy becomes electrical and then light energy.
• Potential energy is stored energy due to an object's position or condition, like a roller coaster at the top of a track.
• Kinetic energy is the energy of motion, such as a flying jet or flowing water.
• People use matter and energy to meet their needs, either by changing energy forms or using matter to produce energy.

Thermal Energy

• Thermal energy is the total kinetic energy of the particles within a substance.
• A substance's thermal energy depends on its temperature and mass.
• Higher temperature means faster particle movement and more thermal energy.
• At the same temperature, a substance with greater mass has more thermal energy because it has more moving particles.

Temperature

• Temperature is the measure of the average kinetic energy of the particles in a substance.
• Temperature differs from thermal energy; a substance can have a lot of thermal energy but a low temperature if its particles move slowly on average.
• A thermometer is an instrument used to accurately measure temperature, using units of degrees.
• Temperature is commonly measured in degrees Fahrenheit (°F) or degrees Celsius (°C).
• On the Fahrenheit scale, water freezes at 32°F and boils at 212°F.
• On the Celsius scale, water freezes at 0°C and boils at 100°C.

Kelvin Scale

• The Kelvin scale, developed by William Thomson (Lord Kelvin), is based on molecular movement.
• The Kelvin scale uses kelvins (K) instead of degrees, with zero (0 K) representing absolute zero, where molecules theoretically stop moving.
• Absolute zero (0 K) is approximately equal to -273°C.
• Lord Kelvin's inventions were crucial for laying the first transatlantic telegraph cable.