Karen Bultitude introduces a set of simple, fun and memorable demonstrations using everyday ingredients to explain meteorological phenomena.
Understanding our impact on the environment is increasingly important, with both scientific and societal implications now covered in various parts of most school curricula. With so much talk about climate change, it is useful to learn about some of the atmospheric phenomena that actually make up our climate.
The following demonstrations help clarify some aspects of these phenomena and bring the concepts to life in an engaging and memorable way. They were developed as part of the British Council’s ZeroCarbonCityw1 campaign to support teachers and scientists throughout the world in explaining basic concepts of environmental science. The demonstrations can be used in a variety of ways: individually, to emphasise particular concepts during class; as a collection, for example as a workshop or demonstration lecture; or as set tasks for students to complete themselves. Further suggestions for activities related to environmental sciences can be found online.
Create your very own mini-cloud.
You can also watch a video of the activity onlinew3.
Clouds are formed when water vapour in the air cools down due to the expansion of the rising air mass, and then condenses to droplets on condensation nuclei such as dust particles, ice or salt. In this demonstration, the condensation nuclei are provided by the smoke from the match, which contains particles of uncombusted hydrocarbons. The temperature is changed by squeezing the bottle: the amount of air within is constant, but squeezing the plastic bottle lowers the volume of the gas, raising the temperature slightly. When you stop squeezing the bottle, the volume increases, thereby causing a slight lowering of the air temperature inside. If the air inside the bottle has a relatively high humidity (which is ensured by adding the teaspoonful of water at the beginning) then the temperature drop is sufficient to cause the water to condense on the dust particles, forming a cloud.
Next time you see a fantastic sunset over an urban area, take a moment to think about what is causing the beautiful colours: its origin actually lies in the tiny smoke particles and other pollutants that have been emitted into the atmosphere. Just like in the plastic bottle, these smoke particles encourage water droplets to condense around them, forming clouds. The scattering of the Sun’s rays amongst the clouds is what creates the beautiful sunset. There are some concerns that air pollution will therefore have a detrimental effect on the weather, since more air pollution leads to increased cloud formation, which could in turn lead to more rain in certain areas and a significant change to wider weather patterns (floods in some areas; droughts in others).
This is a beautiful and fascinating demonstration of turbulent weather effects.
Moving the bottle around causes the soap and water mixture inside to move. The glycerol stearate makes the patterns of flow visible, so you can see the directions in which different parts of the mixture are moving. Smooth lines forming in the liquid indicate laminar flow, which occurs when the liquid is moved slowly. If you make the liquid move faster (or change the direction suddenly) then the observed lines of fluid become more complex: this is turbulent flow.
The Earth’s atmosphere is a kind of fluid that moves much like the liquid inside the whirling orb. Winds interact with the spinning atmosphere and create complex circulation patterns. Understanding the general circulation of the atmosphere is fundamental to the work of many different areas of climate change science – for example, in understanding and reducing the effects of both hurricanes and pollution.
This is a good visual demonstration of thermals – rising currents of warm air.
The burning teabag heats up the air immediately above it. Hot air rises, so the warmer air will gradually rise up above the teabag, creating a rising current of warm air – a thermal. When the teabag has burnt down far enough, the lift from the thermal will be enough to overcome the force of gravity keeping the teabag on the saucer, and so it will lift up.
Thermals are the basis for various weather patterns. The Sun heats up the land, causing thermals to spiral upwards. Thunderstorms are giant thermal systems, and the vortex formation associated with tornados and hurricanes is also based on thermals. As an effect of global warming, more thunderstorms are expected to occur.
This is a good visual demonstration of how tornadoes form.
This demonstration produces a vortex similar to those observed in cyclones, tornadoes and whirlpools. As the water spins around the bottle, there is a downward pull formed due to the water passing through the opening into the empty bottle below. The initial small rotation caused by spinning the bottles gains speed as the water is sucked through the opening. As the rotation speeds up, the vortex forms.
One of the predicted impacts of climate change is global warming: warmer air temperatures mean that thunderstorms are more likely to form, and tornadoes are formed in thunderstorms, where air starts moving in a circle. Updrafts and downdrafts within the thunderstorm force the rotating column of air to become vertical, creating the tornado. An increased number of thunderstorms is therefore likely to cause more hurricanes and tornadoes to form throughout the world.