Why are pools filled with air pollution

City air in a drinking glass

The measured values ​​of air pollutants - such as fine dust or nitrogen oxides - clearly show that air pollution reaches its maximum each year in the cold season. With two drinking glasses and a little smoke, you can simulate why this is so at the kitchen table.

You need that for that

  • two identical tall drinking glasses
  • two cardboard lids to cover the glasses
  • two incense sticks or two thin wooden skewers
  • Lighter / matches
  • Paper, scissors, pens, tape

That's how it's done
Make two mini cities with pencils and paper and stick them on the outside of the glasses with tape. One city stands for winter (you can add “cold” or “winter”), the other for summer (“warm” or “summer”).

Put the winter jar in the refrigerator for an hour. Five minutes before you take it out again, you fill the summer glass with hot tap water. In the five minutes you take two pieces of cardboard that are big enough to cover the jars well. Pierce the pieces of cardboard in the middle and put a stick of incense through each of the small holes. If you don't have incense sticks, you can use small wooden skewers.

Now empty the water from the summer glass and dry it out. Get the winter jar out of the refrigerator. Place them side by side on the table.

Light the incense sticks, let them burn briefly, and then blow them out. Cover the glasses with the pierced cardboard boxes so that the smoking ends of the incense sticks protrude into the glass. Leave the chopsticks in until the glasses are thickly filled with smoke.
If you use wooden skewers: Also light, let it burn a little, blow out and stick the smoking ends into the glasses. While this produces less smoke than incense sticks, it also works.

Then pull the chopsticks out of the box and extinguish the embers. The lids remain on the glasses! Wait a minute. Now remove the lid very slowly so that the air in the glass does not swirl. There must be no other drafts either. Watch the smoke in the glasses.

In the summer glass, the smoke rises quickly and the air in the glass is soon clean again. In the winter glass, the cool air is denser (heavier) and partly stays in the glass, as does the smoke.

You can resolve this situation if you very carefully (without moving quickly) place your hands on the glass. The warmth of your hands warms the glass and thus the air in it. After a short time the smoke begins to rise and the air in the winter glass also becomes clean.

Background info
In the winter glass, the air is a bit cooler compared to room temperature due to the cold glass. In the summer glass the air is warmer because the hot water has warmed the glass. Since cold air has a higher density than warm air, it is heavier. In the winter glass, the air stays inside the glass. The warm air rises in the summer glass. A hot air balloon also uses this effect.

The smoke in the glasses represents the exhaust gases in a city. In the cold air, the exhaust gases also stay at the bottom, in the warm air they rise and distribute themselves upwards.
Exactly the same thing happens in reality: on cold winter days, the cold air gathers in valleys and basins below. It can even be warmer up the mountain than in the valley - this is called inversion. With such an inversion, the air pollutants also remain below, i.e. in the air we breathe directly. For this reason, the highest pollutant values ​​are always measured in the cold season.

When spring arrives, inversions dissolve quickly as the sun is already shining stronger and the air is warming. Your warm hands did the same in an attempt. Wind or precipitation can also dissolve inversions and you will then find lower pollutant values ​​in the air.

This experiment shows the necessity of air pollution control, as otherwise we would lose our exhaust fumes. a. have to breathe in again in winter.

You can find an even clearer model of an inversion here - but you will need more materials.
For schools there are numerous other experiments, games and exercises all about the air in the instruction folder "Our food, the air".

>> back