Knewton Chapter 1: SI Units for Temperature and Time

Temperature

• Intensive property measuring heat energy in an object.
• SI unit for temperature: kelvin (K), no degree symbol used.
• Water freezes at 273.15 K and boils at 373.15 K.
• 0 K represents absolute zero, a theoretical point where all motion ceases.

Celsius

• Celsius (°C) is also recognized in the SI system; uses degree symbol.
• Water freezes at 0°C and boils at 100°C.
• 1 K is equal to 1°C.

Temperature Conversion

• To convert Celsius to Fahrenheit, use: F = (9F/5C) x (C) + 32F.
• To convert Fahrenheit to Celsius, use: C = (F - 32F) x (5C/9F).

Time

• Measurement of process duration.
• SI base unit: second (s).
• Time intervals can be expressed in various prefixes:
  • Microseconds (3 µs = 3 × 10−6 s)
  • Megaseconds (5 Ms = 5 × 10^6 s).

Scientific Notation

• Format: a single digit followed by a decimal and additional numbers.
• Expressed as a number multiplied by 10 raised to an exponent.

Newton

• Unit of force defined as [(kg)(m)]/s².

Base Units of the SI System

• Length: meter (m)
• Mass: kilogram (kg)
• Time: second (s)
• Temperature: kelvin (K)
• Electric current: ampere (A)
• Amount of substance: mole (mol)
• Luminous intensity: candela (cd)

Length

• Represents distance traveled; measured in inches, feet, yards, miles, and meters.
• Small distances expressed in millimeters; large distances in kilometers.

Volume

• Amount of space occupied by an object, primarily measured in liters.

Mass

• Defined as the amount of matter in an object; measured in kilograms (kg).
• Originally based on the mass of a liter of water, now referenced by a metal cylinder stored in France.

Specific Gravity

• Formula: specific gravity = (density of sample substance / density of reference substance).
• Comparative measure of density against a standard.

Water Density

• Density of water is 1 g/ml or 1 g/cm³.

Dimensionless Quantity

• A type of measurement without physical dimension, also known as a quantity of dimension one.
• Common in mathematics, physics, engineering, and economics.

Density

• Defined as mass per unit volume.
• SI units: kg/m³; also expressed in g/cm³ or g/mL.
• Calculation: Density = Mass / Volume.

SI Units Overview

• Key SI units:
  • Kilogram (kg) for mass
  • Second (s) for time
  • Kelvin (K) for temperature
  • Ampere (A) for electric current
  • Mole (mol) for amount of substance
  • Candela (cd) for luminous intensity
  • Meter (m) for distance

Conversion Factors

• Kilo (10³)
• Mega (10⁶)
• Giga (10⁹)
• Tera (10¹²)

Kilogram

• Originally based on the mass of a liter of water, now defined using a stable standard cylinder.

Meter

• Originally defined as a fraction of the Earth’s distance from the equator to the pole, now universally revised.