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PROPERTIES OF MATTER AND THEIR MEASUREMENT
Physical Property : The property which can be measured without changing the chemical composition of the substance is known as physical property.
Example : mass, volume, density, refractive index, boiling point, melting point etc.
Chemical Property : The property which can be evaluated at the cost of matter itself is known as chemical property.
For example oxygen gas can be verified by burning of flame in presence of oxygen gas.
Units for Measurement
All physical quantities have to be measured. The value of a physical quantity is expressed as the product of the numerical value and the unit in which it is expressed.
Fundamental units are those units which can neither be derived from one another nor they can be further resolved into any other units.
The International System of Units (in French Le Systeme International d’Unites– abbreviated as SI) was established by the 11th General Conference on Weights and Measures (CGPM from ConferenceGenerale des Poids at Measures).
The SI system has seven base units.
SEVEN BASIC SI UNITS
The SEVEN FUNDAMENTAL UNITS of measurement in S.I. system.
DEFINITIONS OF SI BASE UNITS
Some quantities are expressed as a function of more than one fundamental units known as derived units. For example velocity, acceleration, work, energy, area, density etc.
Q.1. The temperature at which both the Celsius and Fathrenheit scales will have the same reading is
(b) − 20°
(d) − 40°
Solution. Suppose both read the same value as “x”
or 9x = 5x - 160
or 4x = −160 or x = − 40°
Q.2. Pressure is determined as force per unit area of surface. The SI unit of pressure, pascal is as shown below:
1Pa = 1Nm−2 If the mass of air at sea level is 1034 g cm-2, the pressure in pascal is
(a) 1.01 x 106
(b) 1.01 x 107
(c) 1.01 x 105
(d) 1.01 x 105
Solution. Pressure is the force (i.e., weight) acting per unit area But weight = mg
= 1.01332 x 105 Pa ≅ 1.01 x 105 Pa
Q.3. The prefix femto stands for
Solution. 1 femto = 10-15
Q.4. N kg-1 is the unit of
Solution. Force = mass x acceleration.
Hence, a = F / m = N / kg = N kg-1.
Q.5. Which of the following is correct?
(a) 1 L = 1 dm3
(b) 1 L = 10 dm3
(c) 10 L = 1 dm3
(d) 1 L = 1 m3
Solution. I L = 1000 cm3 = 1000 (0.1dm)3 =1dm3.
Q.6. The units, nanometer, Fermi, Angstrom and attometre, Arrangement in decreasing order are expressed as
(a) Angstrom, nanometer, Fermi, attometre
(b) Fermi, attometre, angstrom, nanometer
(c) Nanometer, angstrom, Fermi, attometre
(d) Attometre, angstrom, Fermi, nanometer
Solution. 1 nm = 10-9 m, 1 fermi =10-15 m,
1 A° = 10-10 m, 1 attometre = 10-18 m.
Q.7. Dimensions of pressure are same as that of
(c) Energy per unit volume
(d) Force per unit volume