Monday, August 22, 2011

VII science Hots Questions

Q. Is shampoo acidic or basic? 

Shampoo is generally made by the salts of a weak acid and a strong base, so they're somewhat basic. Shampoos usually are at pH 5.5 because at slightly acidic pH the scales on a hair follicle lay flat making the hair feel smooth and look shiny. Citric acid is used to adjust the pH down to 5.5 (is). It is a fairly weak acid which makes the adjustment easier.

Q. Why government has put ban on the sale of shahtoosh shawls?

Shahtoosh shawl, made from the wool of endangered Tibetan antelope, Chiru which is a rare animal Therefore, government has put ban on the sale of shahtoosh shawls for the purpose of conservation and protection

Q. Why is sericulture not considered on eco-friendly practise?

Sericulture not considered on eco-friendly practice because during sericulture silk worm is boiled to get silk fibres. Vapours emitted from the boiling cocoon release toxic fumes that pollute the atmosphere contribute to respiratory problem.

Q. Why is shearing usually done in summer?

Shearing is usually done in summer because ships do not require insulating material in summer.

Q. Is burning of candle physical or chemical change or both?

Burning of candle is both. When candle burn wax melts that is a physical change but some wax burn and produce gas this is a chemical change.

Phenomena during the candle burning: 
- melting (physical phenomenon)
- evaporation (may be considered a chemical but also a physical phenomenon)
- oxidation - reaction with oxygen, burning (chemical phenomenon)
- thermal decomposition (chemical phenomenon)

Q. The atomicity of oxygen in ozone is 1.5 times that of oxygen in oxygen molecule derive the formula of ozone. 

Atomicity of oxygen in oxygen molecules = 2

Atomicity of oxygen in ozone molecules = 1.5 x 2=3

Hence the formula of ozone = O3

Q. Why iron gates are painted? 

Iron gates are painted to protect from moisture and air and hence prevent.

Q. Why are toothpastes basic in nature?

In our mouth bacteria produce acid which dissolves enamels therefore prevent acid formation we use toothpastes. The main job of a toothbrush & toothpaste is to remove Plaque , a thin film formed by bacteria on teeth & gums.

Q. Decide which is more acidic or more basic

Strong acid + strong Base ----> neutral salt pH= 7

Weak acid + strong Base ---> Basic salt pH>7

Strong acid + strong Base --> Acidic salt pH< 7

Q. Why does thick glass tumbler crack when you pour hot tea into it?

When you pour hot tea into thick glass tumbler , inner surface expand more than outer surface as glass is bad conductor of heat. Hence unequal expansion crack glass tumbler.

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