General Science Questions

The air around us is a mixture of gases, mainly nitrogen and oxygen, but containing much smaller amounts of water and other gases.

Earth's atmosphere is composed of many gases. Their percentages by volume is given by::

 
78% Nitrogen,

21% Oxygen,

0.9% Argon, and

0.03% Carbon dioxide 

And very small percentages of other elements.

Haemoglobin is a protein what carries oxygen in the blood and contains iron metal in it.

Yes, we know that water is a universal solvent.

Water can moderate temperature because of the two properties: high-specific heat and the high heat of vaporization.

Water is a polar molecule that has a high level of polarity and attraction to ions and other polar molecules.

Hence, all the above given options are the properties of water.

Crystal size in igneous rocks is determined by rate of cooling i.e, the time taken by magma to cool down. 

Hence, the slower the rate of cooling the larger the crystals. The faster the rate of cooling the smaller the crystals.

Potentially hazardous foods are foods that might contain food poisoning bacteria and are capable of supporting growth of these bacteria or formation of toxins to levels that are unsafe for consumers, if the foods are not stored at correct temperatures. Toxins are poisonous chemicals produced by some types of bacteria.

The food can be left at room temperature until it reaches 60 deg C because food-poisoning bacteria will not multiply at 60 deg C or above. However, do not leave food cooling at room temperature unless you are sure that the temperature of the food is still at least above 60 C.