Why do the tea particles spread out quicker in hot water then cold water?

Tea particles spread out quicker in hot water than cold water due to the phenomenon known as Brownian motion. Brownian motion refers to the random motion of particles suspended in a fluid (such as water) resulting from their collision with the fluid molecules.

In the context of tea, when tea leaves or tea bags are immersed in water, the tea particles (such as tannins and other soluble substances) are released into the water. These particles undergo Brownian motion, causing them to move randomly in all directions.

The higher the temperature of the water, the more vigorous the Brownian motion becomes. This is because the increased temperature causes the water molecules to move faster and collide with the tea particles more frequently, resulting in more rapid diffusion and spreading out of the tea particles.

In cold water, the Brownian motion is less pronounced due to the slower movement of water molecules. As a result, the tea particles diffuse more slowly, leading to a slower spreading out of the tea particles and a weaker tea flavour.

Therefore, using hot water for brewing tea results in faster extraction and diffusion of the tea particles, resulting in a stronger and more flavourful cup of tea compared to using cold water.