Why there is water droplets on glass of water in winter?

Water droplets can form on the surface of a glass of water in winter due to a combination of factors related to temperature and humidity. This phenomenon is commonly known as condensation, and it occurs when warm, moist air comes into contact with a cooler surface.

Here's how it happens:

Temperature Difference: In the winter, the outside air is typically colder than the indoor air. When you bring a glass of water from a warmer indoor environment to the colder outdoor air, the temperature difference causes the surface of the glass to cool down.

Cooling of Air Next to the Glass: As the glass cools, it also cools the air immediately adjacent to its surface.

Relative Humidity: The indoor air often contains moisture in the form of water vapor. This moisture content is known as humidity. When the warm, humid indoor air comes into contact with the cool glass surface, the air next to the glass cools down. Cold air cannot hold as much moisture as warm air, so the relative humidity of the air near the glass increases.

Dew Point: When the relative humidity reaches a critical point known as the dew point, water vapor in the air begins to condense into liquid water droplets on the cooler glass surface. The dew point is the temperature at which air becomes saturated with moisture, causing condensation to occur.

Water Droplet Formation: As the air cools and its relative humidity increases to the dew point, water molecules in the air slow down and come together to form tiny water droplets on the glass surface. These droplets accumulate, causing the glass to appear "sweaty" with moisture.

This condensation on the glass is a common occurrence in winter, especially when there is a significant temperature difference between the inside and outside environments. It can also happen on windows, mirrors, and other cold surfaces. To prevent or reduce condensation, you can improve insulation and ventilation in your home, which helps maintain a more even indoor temperature and humidity level.