Properties of Matter and their Measurement
Properties can be classified in to two types
- Physical properties
- Chemical properties
The properties which can be measured or observed with out changing the identity or the composition of the substance is called physical properties
colour, odour, melting point, boiling point, density etc.
The properties which require chemical change is called chemical properties. Chemical properties are characteristic reactions of different substances.
Acidity or basicity, combustibility
There are two different systems of measurement
- The English system
- The Metric system
Mass and weight
The amount of matter present in a substance is called mass of a substance.
Weight is the force exerted by the gravity on an object.
Mass of a substance is constant. Weight may vary from place to place due to gravity.
Mass of a substance can be determined very accurately.
SI unit for mass - kilogram
The unit for volume - (length)3
In SI system unit is - m3
In laboratories only smaller volumes are used. Hence, volume is often denoted in cm3 or dm3 units.
Density of a substance is its amount of mass per unit volume
So, SI units of density can be obtained as follows
SI unit of density = SI unit of mass
SI unit of volume
= kg/m3 or kgm-3
This unit is quite large and a chemist often expresses density in gcm-3, where mass is expressed in gram and volume is expressed in cm3.
There are three common scales to measure temperature
- 0C (degree Celcius)
- 0F (degree Fahrenheit)
- K (Kelvin)
- Generally, the thermometer with Celsius scale are calibrated from 0oC to 1000 where these two temperatures are the freezing point and the boiling point of water respectively
- The Fahrenheit scale is represented between 320 to 2120
0F = 9/5 (0C) + 32
The Kelvin scale is related to Celsius scale as follows
K = 0C + 273.15Important points
- Temperature below 00C are possible in Celsius scale
- In Kelvin scale, negative temperature is not possible.