States of Matter

In Chemistry, a mixture is a material system made up of two or more different substances which are mixed but are not combined chemically. Mixture refers to the physical combination of two or more substances, the identities of which are retained and are mixed in the form of alloys, solutions, suspensions and colloids.

Air is an example of homogeneous mixture.

A pure substance is defined as one which contains only one kind of atoms or molecules. Based upon the nature of constituent particles, it is of two types, i.e. elements and compounds.

Below freezing point, enzymes become inactivated (option A) because molecular motion virtually stops. They are not destroyed - enzyme activity returns when temperature rises above freezing. The 'activated' option incorrectly suggests cold enhances enzyme function.

A thin layer of oil on water is called oil slick. Oil slicks float on oceans and seas, covering them with a thick film of crude or refined petroleum oil. When freight ships carrying thousands of tons of fuel crash, malfunction, or encounter harsh weather, they spill enormous amounts of oil into the water. 

Ptyalin of saliva acts best in pH 6.7

Water lost in transpiration is pure water. It does not contain any solute particles (minerals and salts). 

This is the correct answer.

This is the correct answer as both salt and sand are solids and and do not show diffusion. 

This is the correct answer as this statement is correct. 

As the pressure decreases the soild carbon dioxide is converted into gaseouse form.

This is the correct answer. 

This is the correct answer. Glyerine has highest density among given options.

This is the correct answer as both statements are correct.

This is the correct answer as this statement is correct. Latent heat of vapourisation is the heat energy required to change 1 kg of a liquid to gas at atmospheric pressure at its boiling point.