A pure substance is made up of
Only one kind of molecules
Two or more kinds of molecules
Different types of molecules
None
Which of the following property is not considered when the components of a mixture is separated ?
Density
Energy - change
Volatile nature
Boiling point
Which of the following mixtures will be the most difficult to separate ?
Iron filings + sand
Sand + water
Saw dust + stones
Nitrogen + hydrogen
Choose the substance that shows sublimation
Napthalene
Toluene
Kerosene
Water
Pure substances possess
Variable melting points and boiling points
Nonuniform
Variable properties
Fixed melting points and boiling points
A few coloured glass pieces that are big in size are mixed with sugar. The easiest way to separate them is
Heat the mixture
Add the mixture to water
Handpick the glass pieces
Handpick the sugar particles
A compound has
Only one kind of atom
Only one kind of element
A mixture of elements and molecules
The process by which a solid changes directly into gas is called
Decantation
Sublimation
Condensation
Sedimentation
Identify the mixture from the following
Carbon dioxide
Iron
Hydrogen
Air
Winnowing is useful only when
Two solids have different melting points
Two solids have different boiling points
Two solids have different magnetic properties
Two solids have different weights