GOB Chemistry: Scientific Method, Significant Figures, and Metric Conversions

Scientific Method and Hypotheses

Understanding Hypotheses in Science

The scientific method is a systematic approach used in scientific study. It involves making observations, forming hypotheses, conducting experiments, and drawing conclusions. A hypothesis is a testable statement that predicts an outcome based on prior knowledge and observations.

• Hypothesis Definition: A hypothesis is a proposed explanation for a phenomenon, which can be tested through experimentation or observation.

• Characteristics of a Valid Hypothesis:

  • It must be testable and falsifiable.

  • It often takes the form of an "if...then..." statement.

  • It should be based on prior knowledge or observations.

• Example: "Mountain lion populations will increase if more habitat is protected." This is a valid hypothesis because it predicts a specific outcome that can be tested.

Significant Figures and Scientific Notation

Writing Numbers in Scientific Notation

Scientific notation is a way of expressing very large or very small numbers using powers of ten. Significant figures are the digits in a number that carry meaning contributing to its precision.

• Scientific Notation Format: $a \times 10^n$, where $1 \leq a < 10$ and $n$ is an integer.

• Rules for Significant Figures:

  • All nonzero digits are significant.

  • Zeros between nonzero digits are significant.

  • Trailing zeros in a number with a decimal point are significant.

• Example: 205,000 written in scientific notation with three significant figures is: $2.05 \times 10^5$

Metric System and Unit Conversions

Converting Between Metric Units

The metric system is a decimal-based system of measurement used in science. Understanding how to convert between units is essential in chemistry.

• Common Metric Prefixes:

  • micro- ($\mu$): $1 \mu m = 1 \times 10^{-6}$ meters

  • deci- (d): $1 dm = 1 \times 10^{-1}$ meters

• Conversion Steps:

  1. Convert micrometers ($\mu m$) to meters (m): $8100.0 \ \mu m \times \frac{1 \ m}{1 \times 10^6 \ \mu m} = 8.1000 \times 10^{-3} \ m$

  2. Convert meters to decimeters (dm): $8.1000 \times 10^{-3} \ m \times \frac{10 \ dm}{1 \ m} = 8.1000 \times 10^{-2} \ dm$

• Final Answer: $8100.0 \ \mu m = 8.1000 \times 10^{-2} \ dm$

The Periodic Table of the Elements

Overview and Organization

The Periodic Table organizes all known chemical elements by increasing atomic number and groups elements with similar chemical properties into columns called groups or families. Rows are called periods.

• Groups: Vertical columns (e.g., Group 1: Alkali metals, Group 17: Halogens).

• Periods: Horizontal rows, indicating increasing atomic number.

• Element Information: Each box typically contains the element's symbol, atomic number, and atomic mass.

• Example: Sodium (Na) is in Group 1, Period 3, with atomic number 11.

Prefix	Symbol	Factor
micro-	μ	$10^{-6}$
milli-	m	$10^{-3}$
centi-	c	$10^{-2}$
deci-	d	$10^{-1}$
kilo-	k	$10^{3}$

Additional info: The worksheet covers foundational GOB Chemistry skills: scientific reasoning, significant figures, metric conversions, and basic periodic table structure. Mastery of these concepts is essential for success in general, organic, and biological chemistry courses.