Using Energy from Heat and Measuring Temperature

Using Energy From Heat

• Humans have used energy from heat throughout history, developing various heating methods.
• Key examples include: ancient fire (7000 BC), Roman central heating (100 BC), fireplaces and chimneys (1300s AD), cast iron stoves (1700s), coal-burning central heating (late 1700s), forced-air heating (late 1800s), and electric heaters (1906).

Measuring Temperature

• Two senses, sight and touch, give a relative idea of temperature.
• The same temperature can feel different due to relativity. Body temperature accustoms itself, affecting perception from touch.
• 0°C is equivalent to 273.15 Kelvin.
• The two main temperature scales are Celsius and Kelvin.
• Thermometers are more reliable tools for measuring temperature than sense perception.

Measuring Extremes

• Thermometers have three common elements: a sensor (material affected by temperature changes), a signal (like an electrical current), and a responder (displays data – pointer, light).
• Different sensors include thermocouples (two twisted wires creating current), bimetallic coils (two metal strips expanding at different rates), and recording thermometers (a bimetallic coil strip with a lever and drum graph).
• Infrared thermography uses infrared radiation to capture and image temperature.

The Particle Model, Temperature and Thermal Energy

• All matter consists of tiny particles too small to see.

• Particles have spaces between them.

• Particles are always in motion (vibrating, rotating, moving).

• Particles in a pure substance are identical. Different substances have different particles.

• Particles attract each other, with varying force types and strengths.

• Temperature indicates average particle energy.

• Motion increases with higher temperature; decreases with lower temperature.

• Energy is the ability to cause change.

• Thermal energy is the total kinetic energy (energy of motion) of all the particles in a substance.

The Law of Conservation of Energy

• Energy cannot be created or destroyed but can transform or transfer between objects or substances.

Expansion and Contraction

• As particle average energy increases, so do the spaces between particles (expansion). The opposite happens when energy decrease (contraction)
• Different states of matter behave differently when heated or cooled (Solid, Liquid, Gas).
• The principle of expansion and contraction is important in civil engineering (constructing buildings that account for expansion and contraction due to temperature changes, and creating metal expansion joints between parts of highway, roads, railways...).