PS9.1 - Temperature and heat

Temperature scales

Celsius, Fahrenheit and Kelvin scales are used to measure temperature.

Heat refers to the ambient kinetic energy of the particles in the environment under study. Heat is experienced by the sensory cells, which pass information to the central nervous system regarding the vibrations of the particles.

Temperature scales give us a numerical value of the average kinetic energy of the particles.

The Kelvin scale is an absolute measure of the average kinetic energy in which the Kelvin value is directly proportional to the energy. Zero on the Kelvin scale means that there is no kinetic energy in the particles.

Interconversion of temperature scales

To convert Celsius to Kelvin you must add 273.

To convert Kelvin to Celsius you must subtract 273.

PS9.2 - The atmosphere

The layers of air that we need to survive are known as the atmosphere. The solid land mass is called the lithosphere and the oceans and rivers, the hydrosphere. Together they make up our planet.

The lowest layer of the atmosphere is where all of the weather happens, it is known as the troposphere.

There are several gases in the atmosphere:

• Nitrogen, about 79%
• Oxygen, about 20%
• Argon, about 1%
• Carbon dioxide, between 0.02 and 0.04%

The problem is that every one of the 8 billion people on the earth rely on the air for survival and that there are many other substances that are released into the air that makes survival very difficult.

PS9.3 - Incomplete combustion & PM

Most energy resources are based on fossil fuels and rely on combustion. The hydrocarbons present in the fossil fuels burn in air to produce carbon dioxide and water vapour.

For example, natural gas (methane)

CH₄ + 2O₂ → CO₂ + 2H₂O

However, if the supply of air is limited then the combustion is incomplete and produces carbon monoxide and carbon micro-particulates (PM)

These carbon microparticulates are so small that they remain suspended in the air and become a major health hazard, causing bronchial complaints, asthma and cancer.

Most developed countries monitor these micro-particulates in cities and try to minimise their effect.

They are measured in ppm (parts per million parts of air) and determined according to the size of the microparticulates in nanometres (nm, 10^-9 m).

Particulate matter with particle diameter up to 50 nm is known as PM₅₀

PS9.4 - Weather

Pressure, density, altitude and buoyancy

PS9.5 - Pollution

NOx and SO₂

PS9.6 - Working with gases