# CHEM 208 Lecture Notes - Lecture 2: Atomic Number, Nanosecond, Si Derived Unit

## Document Summary

Module 2 the scientific method and matter. The approach that scientists use to formulate and establish scientific laws includes a set of steps, such as explaining the experimental observations and subsequent measurements in terms of a model and then rectifying the model with additional experiments. Two components: a measured quantity (numerical value) with an appropriate unit; ex, temperature). Hypothesis: a tentative explanation to account for the observations of an experiment. The validity of the hypothesis needs to be confirmed via repeated and controlled experiments. Scientific notation: a mathematical expression in which a number is expressed as: n x 10+n where n contains only one nonzero digit to the left of the decimal and n is an integer. 1 inch = 2. 54cm) these have infinite number of significant figures. Rules: all nonzero digits are significant figures, ex. 23. 6 = 3, 123. 45 = 5: counting begins from the left with the first non zero number, ex.