Chemistry SI Units and Measurements PDF

INTRODUCTION ❖ This unit covers basic chemistry concepts: SI units, measurement uncertainties, scientific methods, lab equipment, and safety. Mastery ensures accurate experiments. Key Highlights FORMULAS AND EQUATIONS: Density:...

INTRODUCTION ❖ This unit covers basic chemistry concepts: SI units, measurement uncertainties, scientific methods, lab equipment, and safety. Mastery ensures accurate experiments. Key Highlights FORMULAS AND EQUATIONS: Density: 𝑑=𝑚𝑉 , where d is density, m is mass, and 𝑉 is volume. Temperature Conversion: 𝐾=℃ +273.15 𝟓 ℃=𝟗(℉−32) Volume of a Sphere: 𝟒 𝑉=𝟑 𝝅𝒓𝟑 Unit One Precision and Accuracy Precision: The consistency of repeated measurements. Accuracy: How close a measurement is to the true value. ▪ Using a balance to measure mass consistently close to the true value demonstrates both precision and accuracy. SI Units and Their Prefixes SI Units: There are seven base SI units used in chemistry meter - m ampere - A candela - cd kilogram - kg kelvin - K second - s mole - mol Prefixes SI units use prefixes to indicate multiples or fractions. such as : kilo(k) 103 milli (m) 10−3 nano (n) 10−9  Scientific Notation ❖ Used for very large or very small numbers to simplify calculations. Example: 6.02×1023 for Avogadro's number or 3.27×10−22 for a small mass. Significant Figures Rules: ❖ Non-zero digits are always significant. ❖ Any zeros between significant digits are also significant. ❖ Leading zeros are not significant. ❖ Trailing zeros in a decimal number are significant. Derived SI Units Quantity Definition of Quantity SI Unit Area Length squared m² Volume Length cubed m³ Density Mass per unit volume kg/m³ Unit One Speed Distance traveled per unit time m/s Acceleration Speed changed per unit time m/s² Force Mass times acceleration of object kg.m/s² (= newton, N) Pressure Force per unit area kg/(m.s²) (= pascal, Pa) Energy Force times distance traveled kg.m²/s² (= joule, J) Uncertainty in Measurements ❖ Systematic Uncertainties: Consistent deviations that can be corrected, such as calibration errors. ❖ Random Uncertainties: Unpredictable variations that can be reduced but not eliminated. ❖ Significant Figures: The meaningful digits in a measurement, indicating the precision of the measurement.  SUMMARY SI Units: Seven base units (m, kg, s, A, K, mol, cd) and prefixes (kilo, milli, nano) for multiples and fractions. Measurement Uncertainty: Systematic (correctable) and random (reducible) uncertainties, and significant figures for precision. Precision and Accuracy: Consistency and closeness to true values in measurements. Scientific Notation: Simplifies calculations for large/small numbers. that the temperature scale in science, called Kelvin, starts from the coldest possible temperature, which is -273.15°C? It's so cold that atoms stop moving! Unit One