Some Basic Concepts of Chemistry Test - 1

Pure substances have fixed composition..These may be both  (ie. either elements or compounds ) . The law of constant composition holds good for such substances .

Scientific notation is conveniently used to represent extremely large or even very small numerical values. It is an exponential notation in which any number can be represented in the form,  N x 10n, where n is an exponent having positive or negative values and N can vary between  1 and  10, but not  10 itself.

At macroscopic level matter is classified as mixture or pure substances
A mixture contains two or more components (in any ratio )  present in it , for example -- sugar solutions in water , tea , air , alloys like brass ,bronze etc.
Pure substances (viz. copper  , silver , gold  , water , glucose etc . )   have  fixed composition .
The constituents of pure substances can not be separated by simple physical methods.

Significant  digits are certain digits that have significance or meaning to certain digits in a number . Such digits help scientists to use them with more precise information about measurement and other numeric data. These digits also help them in rounding off very large or very small number

Chemistry does not deal in explaining superconductivity.

• In superconducting materials, the characteristics of superconductivity appear when the temperature is lowered below a critical temperature.
• The onset of superconductivity is accompanied by abrupt changes in physical properties which are more related to phase transitions of the material.

These aspects of studies in properties of materials are better related to studies in the fields of Physics, even though principles involved in Chemistry & Physics go hand to hand.