Nature of Science & Measurement

Science & Its Branches

• Science: investigation/exploration of natural events + resulting knowledge

• Branches- Physical Science – study of matter & energy

  • Earth Science – processes on/within Earth

  • Life Science – organisms & their processes

Observation Types

• Qualitative – descriptive, no numbers (color, texture, smell)

• Quantitative – numerical measurements (length, mass, temperature)

Key Inquiry Terms

• Hypothesis – testable, possible explanation for an observation

• Inference – explanation based on prior knowledge/experience

• Prediction – statement of next event in sequence

Scientific Law vs. Theory

• Law: describes a repeatable pattern in nature (what happens)

• Theory: well-supported explanation of observations/events (why it happens)

Experimental Design Essentials

• Independent variable – deliberately changed

  • Example: In an experiment testing fertilizer on plant growth, the amount of fertilizer is the independent variable.

  • Example: To test how temperature affects the rate of a chemical reaction, the temperature is the independent variable.

• Dependent variable – measured response

  • Example: In the same experiment, the plant height or weight (which responds to the fertilizer) is the dependent variable.

  • Example: In the chemical reaction experiment, the time it takes for the reaction to complete is the dependent variable.

• Constants – kept identical for all groups

• Experimental group – receives independent variable

• Control group – normal conditions (baseline)

Core Steps of Scientific Inquiry

• Make observations / inferences → State problem → Form hypothesis → Test → Analyze → Draw conclusions

International System of Units (SI)

• Universal metric system; prefixes change by powers of ten

• Common base units: meter (length), gram (mass), liter (volume), kelvin (temperature)

• Key prefixes (large → small): kilo, hecto, deka, (base), deci, centi, milli

In-System Metric Conversions ("King Henry" slider)

• Visual representation: ${\text{kilo}} \leftrightarrow {\text{hecto}} \leftrightarrow {\text{deka}} \leftrightarrow {\text{base}} \leftrightarrow {\text{deci}} \leftrightarrow {\text{centi}} \leftrightarrow {\text{milli}}$

  • Move decimal right for each step right (multiply by 10).

  • Move decimal left for each step left (divide by 10).

• Move decimal left/right one place per prefix step

• Example: $5\,\text{kg}=500\,000\,\text{cg}$

• Example: $12.54\,\text{km}=1\,254\,000\,\text{cm}$

Metric Conversion Practice

1. Convert $2500\,\text{mg}$ to grams.

2. How many meters are in $0.75\,\text{km}$?

3. Convert $4.2\,\text{L}$ to milliliters.

4. Express $350\,\text{cm}$ in dekameters.

U.S.–Metric Length Equivalents

• $1\,\text{in}=2.54\,\text{cm}$

• $1\,\text{ft}=0.30\,\text{m}$

• $1\,\text{m}=3.28\,\text{ft}$

• $1\,\text{mi}=1.61\,\text{km}$

Percent Error

$\%\,\text{Error}=\left|\frac{\text{Experimental} - \text{Accepted}}{\text{Accepted}}\right| \times 100\%$

Scientific Notation

1. Shift decimal to give 1–10; count places (n)

2. $N = a \times 10^{n}$ ; n>0 for left shift, n<0 for right- Example: $149\,600\,000 = 1.496 \times 10^{8}$

Matter & Its Properties

• Matter: anything with mass & volume (air counts)

• Specific properties (identify substances): color, odor, hardness, boiling point, etc.

• General properties (apply to all matter): mass, volume, density, inertia

Density

$\text{Density}=\frac{\text{Mass}}{\text{Volume}}$

• Units: liquids $\text{g/mL}$ ; solids \text{g/cm^{3}}

• Characteristic for a substance; remains constant for given T & P

Mass, Volume, Density Relationships

• $D = \frac{M}{V}$

• $M = D \times V$

• $V = \frac{M}{D}$

Viscosity

• Resistance of a fluid to flow; high viscosity = flows slowly (e.g., honey)

Volume of Irregular Objects

• Water displacement: volume change in graduated cylinder/drip beaker = object volume

Inertia

• Tendency of matter to resist changes in motion; increases with mass