Clouds are made up of tiny water droplets or ice crystals floating in the air. Class 9

Clouds are made up of tiny water droplets or ice crystals floating in the air. Class 9

Threads of Curiosity (Page 88)

Question 1.

Clouds are made up of tiny water droplets or ice crystals floating in the air. Based on what you know about solutions, suspensions and colloids, what type of mixture do you think clouds are and why? Class 9

Answer:

Clouds are colloids. The tiny water droplets or ice crystals (dispersed phase) are suspended in air (dispersion medium). The particle size is in the colloid range (1-1000 nm). The particles do not settle, the mixture appears uniform, and it shows the Tyndall Effect (the beam of sunlight is visible through clouds). All these are properties of a colloid.

Question 2.

Why do cities with a lot of smoke and dust in the air often look hazy? Class 9

Answer:

Smoke and dust form colloidal mixtures with air. These fine particles (1-1000 nm) scatter light in all directions - this is the Tyndall Effect. The scattering of light by these particles makes the atmosphere look hazy or foggy. This is why polluted cities appear hazy, especially in sunlight.