1405 - CHAPTER 2
THE METRIC SYSTEM
Measurements and Metric system:
The measurement system in science and technology is called the metric system (Systeme
International d’Unites (S.I. system)
Ex: Length (m), Mass (kg), Temperature (Kelvin), Time (s), Amount of Substance (mol),
Electric Current (Ampere), Luminous Intensity (Candela).
Area (m2), Volume (m3), Density (kg/m3), Velocity (m/s)
Some conversions:
109
1 Giga
6
10
1 Mega
103
1 Kilo
102
1 Hecto
10
1 Deka
10-1 (0.1)
1 Deci
-2
10
1 centi
10-3
1 Milli
-6
10
1 Micro
10-9
1 Nano
-12
10
1 Pico
(1meter = 10 Decimeter)
(1meter = 100 Centimeter)
(1meter = 1000millimeter)
(1meter = 1000000micrometer)
(1meter = 109nanometer)
(1meter = 1012picometer)
1 in = 2.54 cm, 1 cu.ft = 28.32 L, 1 lb = 453.59 gm
39.37 in = 1m, 1.057 qt = 1L, 1 ounce = 28.35 g, 1 mile= 1.609 km, 1 gallon = 3.7853 L, 1 dram =
1.772 g.
Q: Express 5ms in sec, 0.05 m in cm, 0.02 m in mm, 0.005 L in mL, 10 cm in pm, 0.045kg/L in
mgs/ml
Q: Make the following conversions using the correct significant figures.
4.18 gal to mL, 250 lb to kg, 2.95 ounces to mg,
Fundamental Properties of Matter
1. Mass
It is a measure of the quantity of matter. SI unit kg.
What is the difference between Mass and Weight? Mass has weight because of gravitational
force. An object’s mass at Mount Everest, at sea level and in space is same. But the weight of
the same object is different at these 3 locations .It is maximum at sea level, less at mount
Everest and least (weightless) in space. Explain the reason.
Q. How many kg, g, and mg are there in 0.60lb calculated to the correct number of significant
figs.
2.Volume
It is the amount of space that a sample of matter occupies. SI unit Liter
Volume of a rectangular solid is calculated as
V = Length x Width x Height
Volume of an irregular solid is measured by immersing in water. The volume of water
displaced by the solid is equal to its volume.
Express the following.
a. 452ml in liter b.2.89L in ml c. 3.8 gallon in ml.
Density
Density of a substance is defined as the mass per unit volume.
Density = Mass (g)
Volume (ml)
Order of density of a substance
Solid > Liquid > gas
A rise in temperature decreases the density of a substance because though the mass remains
same, volume increases with rise in temperature.
Density of urine is measured to evaluate the kidney function. Density of urine increases as the
amount of dissolved solids increase.
Q. What is the volume of 250.0 g of acetone whose density is 0.7899 g/cm3?
Q: Calculate the mass of 135.0ml of a liquid that has density of 0.8758g/ml at 200C
Specific Gravity =
Density of test liquid
Density of reference liquid
Specific gravity has no units. Hydrometers are used to measure the specific gravity.
Density and “Fitness” of water:
Usually density of liquids decreases with rise in temperature. However, in the case of water it
undergoes a unique change. On increasing the temperature from 00C the density of water rises
and becomes maximum (1.000g/cc) at 3.980C. Above this temperature, the density goes on
decreasing. The density of ice is lower than liquid water, therefore ice floats on water.
Because of this property, as the environmental temperature decreases, water at 40C, sinks to
the bottom of rivers and seas, surrounded by lighter water at lower temperature and finally ice
at the surface.
Temperature
It is the measure of the “hotness” or “coldness” of the body. It is measured using a device
called the Thermometer. The SI unit is Kelvin. Other common units are Celsius and
Fahrenheit.
Kelvin= 0C + 273.15
0C = (0F – 320F) x (5/9)
0F
= 0C x (9/5) + 320F
Q: Convert the following:
a. 680F to 0C
b.450F to 0C
0
0
d. –40 F to C
c. 1250C to 0F
d. 270C to K
e. -2730C to K
Heat and Calorimetry:
Heat is a form energy. The SI unit heat is Joule (J). The commonly used non-SI unit is
calorie.
1 calorie = 4.184 J. 4.184 j is the heat required to raise the temperature of 1 g of water
through 10C.
Specific Heat:
It the quantity of heat required to raise the temperature of 1 g of a substance through 10C.
Cp =
Heat (J)
Mass (g) x
T0C
t = tf - ti
Water has the highest specific heat among the common liquids.
Specific Heat and “ Fitness’ of water:
Mammals and birds are endotherms; they derive their body temperature from internal
metabolic activities. A constant elevated temperature leads to higher and more efficient rate
of metabolism. The heat produced in the body by metabolic activities is absorbed by water,
which is the chief component of living cells. Because of water’s high specific heat,
temperature is controlled in living organisms.
Q: How many J are required to raise the temperature of 0.750 kg of a substance whose
Specific heat is 0.220 J/ g 0C from 13.00C to 68.00C.
Q: Calculate the Specific heat of 32 g of a substance that requires 22.0 J to raise its
temperature from 180C to 280C.