Chalk powder, which primarily consists of calcium carbonate, is relatively insoluble in water. While it can react very slowly with water over time to form soluble calcium bicarbonate, the solubility of chalk powder in water is extremely low, making it effectively insoluble for most practical purposes.

1. Sunlight has seven colors.

2. Seven colours – violet, indigo, blue, green, orange, yellow and red.

3. Violet has the shortest wavelength, while red has the longest wavelength.

4. The seven colours contained in sunlight can often be seen in rainbows.

5. Rainbows are formed when sunlight passes through raindrops.

1. Kala-azar disease is caused by the protozoa Leishmania donovani.

2. It is a parasitic protozoa that belongs to the class Mastigophora or Flagellata. It is caused by sand fly (Phlebotomus) which causes kala azar or dumdum fever.

lactic acid is one of the end products of anaerobic respiration in humans and some other organisms. During anaerobic respiration, which occurs in the absence of oxygen, glucose is partially broken down to generate energy. In the absence of oxygen, cells can convert pyruvate, a product of glycolysis, into lactic acid. This process, called lactic acid fermentation, helps generate energy in the absence of oxygen but also leads to the accumulation of lactic acid, causing muscle fatigue and soreness.