Base Units, Metric System and Measurement

• Measurement involves assigning a numerical value to a physical property
• Units provide a standard for consistent comparison
• The International System of Units (SI) is the modern version of the metric system

Base Units

• Mass is measured in Kilograms (kg)
• Electric Current is measured in Amperes (A)
• Time is measured in Seconds (S)
• Temperature is measured in Kelvin (K)
• Amount of a substance is measured in Moles (mol)
• Length is measured in Meters (m)
• Luminous intensity is measured in Candela (cd)
• The Metric System is based on decimal multiples, which simplifies calculations and uses powers of ten

Prefixes and Notation

• Prefixes are independent of the base unit and modify it without changing its value during conversions

Uncertainty in Measurement

• Random error involves fluctuations due to uncontrollable factors
• Systematic error involves consistent errors due to faulty tools or methods
• Precision is the consistency of repeated results, it measures reproducibility
• Accuracy measures how close a value is to its "true" value

Significant Figures

• Significant figures include all certain digits plus one uncertain digit
• Nonzero digits are always significant
• Zeros between nonzero digits are significant
• Zeros to the left of the first nonzero digit are not significant
• If a number is less than 1, only the zeros at the end or between nonzero digits are significant
• Leading zeros in numbers less than 1 are not significant
• If a number is greater than 1, all zeros to the right of the decimal point are significant
• Trailing zeros for numbers without a decimal point may not be significant
• Zeros used as placeholders in large numbers without a decimal point are not significant

Scientific Notation

• Scientific notation simplifies very large or small numbers
• The process expresses a number as a product between 1 and 10 and a power of 10
• A positive exponent indicates the decimal point moved to the left
• A negative exponent indicates the decimal point moved to the right

Conversion of Units

• Dimensional analysis uses a conversion factor as a ratio to change data to the desired unit
• Write the unknown quantity with its units
• Identify necessary conversion factors
• Multiply known quantities by conversion factors, canceling units to find the unknown unit

Density Measurement

• This measurement involves mass, volume, and temperature
• Mass is the quantity of matter in an object (g/kg)
• Volume is the amount of space a substance occupies
• Temperature measures how hot or cold an object is, K = °C + 273.15 or K = (°F + 459.67) 5/9
• Density is the ratio of mass to volume