Ch.13.measurements
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This document discusses different units used to measure physical quantities like length, mass, time, and temperature in the International System of Units (SI). It explains that the standard units for length, mass, and time are the metre, kilogram, and second, respectively. Smaller and larger units are defined as decimal multiples or submultiples of these standard units. Methods for measuring time, temperature, and different liquids used in thermometers are also outlined.
Ch.13.measurements
- 2. Measuringlength The standard SI unit for measuring length is metre. Unit Symbol Number of meters Kilometre km 1000 m Metre m 1 m Centimetre cm 0.01 m Millimetre mm 0.001 m Micrometre μm 0.000 001 m nanometre nm 0.000 000 001 m
- 3. MeasuringMass The standard SI unit for measuring mass is kilogram. Unit Symbol Number of kilograms megaton Mt 1000 000 000 kg ton t 1000 kg Kilogram kg 1 kg Gram g 0.001 kg milligram mg 0.000 001 kg
- 4. Balance scales Top pan balance Spring balance
- 5. Measuringtime The standard SI unit for measuring time is the second. Unit Symbol Number of kilograms Day d 86 400 s (1440 min. or 24 h) Hour h 3600 s (60 min.) Minute min 60 s Second s 1 s millisecond ms 0.001 s
- 6. MeasuringTemperature The hotness or coldness of a substance is measured by taking its temperature. The temperature of a substance is measured on a scale. The most commonly used temperature scale is the Celsius scale. Its two fixed points are 0 ⁰C and 100 ⁰C. Laboratory thermometers usually have a scale from -10 ⁰C to 110 ⁰C.
- 7. The lowest possible temperature, known as absolute zero is -273 ⁰C. Temperatures can go as high as millions of degrees Celsius.
- 8. Liquidsinthermometers Two liquids that are commonly used in thermometers are mercury and alcohol. Mercury has a freezing point of -39 ⁰C and a boiling point of 360 ⁰C. Alcohol has a freezing point of -112 ⁰C and a boiling point of 78 ⁰C.