Who is heavier or lighter? Is hot air heavier or lighter than cold air

Cold air is heavy, and we learned in elementary school: "When the air is heated up, the cold air around it flows to replenish it, and the wind is formed." "So, why does the air rise when it is heated?

It turns out that this is because the air expands in volume when heated, and the specific gravity becomes lighter than the surrounding cold air, and the heavier cold air around it flows over and floats the lighter hot air to it, thus forming a wind.

The heat emitted by the conversion of hot air into cold air is equal to the amount of heat absorbed by the conversion of cold air into hot air. In the process of changing the temperature of the air, the total mass of air and heat in nature does not increase or decrease. However, the volumetric change that occurs in the air during this temperature change causes the air on the ground to flow – generating wind and an inexhaustible supply of wind energy.

Balloon. It's the best proof of that.

Due to: constant pressure, for ideal gases.

In general, actual gases can also be applied} exists, pv=nrt

So, volume is directly proportional to temperature, and density is inversely proportional to temperature.

Because of thermal expansion and cold contraction.

The cold air becomes hot air at the heating side, the volume becomes larger, the mass does not change, so the density becomes smaller.

The cold air is heavy and the hot air is light, and the hot air balloon will rise is the best example, the specific gravity is determined according to the temperature difference, and there is a formula to calculate.

Air conditioning. It should be that the temperature of the hot gas is high, the intermolecular interval is large, and the intermolecular interval of the cold gas is small, so the same volume of cold air and hot air, the cold air contains more molecules, and the cold and hot gas molecules are both molecules of air, so the control variable method is used to know that the air conditioning mass is large.

In addition, the answer can also be made by density, m=pv

Hot air will weigh less as compared to cold air of the same volume.

Analysis: The air expands when heated, and compared with the same volume of cold air, the density becomes smaller and the weight will be lighter. The density of air varies depending on the temperature and pressure.

At one atmosphere, under standard conditions (0, 1 atm), the air density is about. 20 o'clock, take.

Therefore, due to the influence of temperature, the air density of hot air is less than that of cold air, and the weight of hot air will be lighter for the same volume.

Influencing factors and conversion formulas of atmospheric air density

Atmospheric mass density depends on air temperature, air pressure, and air humidity, and is usually not directly obtained, but is calculated. Its value decreases exponentially with altitude. The density of the air around us is g·l-1 under standard conditions (0 (273K), 101kPa).

The standard value of atmospheric density at sea level is kilograms per cubic meter.

Conversion formula: according to PV=NRT, where t is the temperature (in k) and p is the pressure (in ATM), so the air density: air density actual pressure standard physical atmospheric pressure) (273 actual absolute temperature), absolute temperature Celsius temperature 273.

In terms of weight, both are air, equally heavy.

But if "heavy" refers to density, cold air is denser.