LINE BY LINE NOTES FOR ENGLISH MEDIUM STUDENTS

1. The comparison of unknown quantities with some known quantities is known as measurement.
2. Measurement of a quantity has two parts:  a number and its unit.
3. Distance between one end and the other desired end is called as length
4. The standard unit of length is metre. It is represented by letter 'm'
5. Very small length can be measured in mm and cm.
6. Large length can be measured  in metre and kilometre
7. The sake of uniformity, scientists all over the world have adopted a common set of units to express measurements. This system is called as the International System of units or SI units. Image screenshot
8. Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight.
9. Area is obtained by using two lengths. 
10. Area = Length × Breadth.
11. Volume is a derived quantity and it can be measured from measuring lengths.
12. volume of the box = l × b × h
13. Liquids take the shape of the container in which they are kept.
14. Graduated cylinders, beakers, pipettes and burettes are available for measuring exact volumes of liquids.
15. The volume of liquid is usually measured in litres.
16. volume is the space occupied by an object.
17. 1ml = 1 cubic cm
18. Gases expand to fill the container into which they are placed.
19. When you compress, a gas you can make the same gas to occupy lesser space.
20. SI unit for Volume of solid is cubic metre
21. Liquids and gases are usually measured in litres
22. Liquids and gases are also can be measured in m³ or cubic metre.
23. While using ruler, the accurate measurement can be arrived by avoiding three types of possible errors.
24. Volume of irregular objects can be measured by water displacement method.
25. Electronic balance is an instrument to provide accurate measurement of mass correct up to milligram.
26. The weight is directly proportional to the mass on earth's surface. On moon where the gravitational force is lesser than earth, the weight will reduce but the mass will remain the same. The moon’s gravitational pull is one sixth of the earth’s pull. Thus objects weigh six times lighter on the Moon than on the Earth.
27. Mass is the measure of the amount of matter in an object. Weight is the gravitational pull experienced by the mass.
28. The SI unit of mass is kilogram. It is represented by the ‘kg’.
29. Bigger weights are measured in tonne or Metric Tonne.
30. A beam balance works by comparing the mass of an object to that of known mass (called a standard mass)
31. An electronic balance is a device used to find accurate measurements of weight.
32. An electronic balance is used very commonly in laboratories for weighing chemicals to ensure a precise measurement of those chemicals for use in various experiments.
33. In earlier days people used sand clock and sundial to measure the passage of time during the day. The shadow cast by a stick can be used to estimate time. One can also use a vessel with a small hole for computing time. Take a vessel or bottle with a small hole in it and fill it with water. The time taken for water to drain can also be used as a measuring device. These are rough methods for counting passage of time. We can use electronic clock, stopwatch and other instruments to count even smaller durations of time.
34. An odometer is a device used for indicating distance travelled by an automobile.
35. The metric system or standard set of units was created by the French in 1790.
36. A ruler or scale, used now a days to measure length was invented by a William Bedwell in 16th century.
37. A standard metre rod made of an alloy of platinum and iridium is placed at the Bureau of weights and measures in Paris. National Physical Laboratory in Delhi has a copy of this metre rod.
38. One kilogram is equal to the mass of a certain bar of platinum-iridium alloy that has been kept since 1889 at the International Bureau of Weights and Measures in Sèvres, France.

SI unit for length is Metre 
SI unit for mass is Kilogram
SI unit for time is Second
SI unit of  area of surface is m2
SI unit of volume of solid is m3

1 m3 = 1 kilolitre (kl or kL)
1cm3 = 1 millilitre (ml or mL) 
1mm3= 1 microlitre (µl or µL)

1000 milligram = 1 gram 
1000 gram = 1 kilogram
1000 kilogram = 1 tonne

1 cm = 10 mm
1 m = 100 cm
1 km = 1000 m