Scientific Measurement & Lab Safety

Why This Matters for Nursing: Accurate measurement is essential for dosing medications, recording vital signs, and interpreting lab results. Lab safety principles apply to clinical settings where you handle hazardous materials and body fluids.

What You Need to Know

Scientific measurement requires precision, accuracy, and proper units. Lab safety protects you and patients from hazards.

🧠 Memory Trick

Metric Prefixes (big to small): "King Henry Died By Drinking Chocolate Milk" Kilo → Hecto → Deka → Base → Deci → Centi → Milli

Significant Figures:

• All non-zero digits are significant
• Zeros between non-zero digits are significant
• Leading zeros are NOT significant

Metric System Review

Base Units:

Prefixes:

Precision vs. Accuracy

Ideal: Both accurate AND precise

Significant Figures

Rules:

1. Non-zero digits are ALWAYS significant: 123 has 3 sig figs
2. Zeros between non-zeros ARE significant: 101 has 3 sig figs
3. Leading zeros are NOT significant: 0.01 has 1 sig fig
4. Trailing zeros after decimal ARE significant: 1.00 has 3 sig figs

Examples:

Lab Safety Equipment

Lab Safety Rules

Before Lab:

• Know emergency procedures and exits
• Read all procedures before starting
• Wear appropriate PPE (Personal Protective Equipment)

During Lab:

• Never eat or drink in lab
• Never smell chemicals directly (waft with hand)
• Point test tubes away from yourself and others
• Report all spills and accidents immediately
• Wash hands after handling materials

Chemical Safety:

• Read all labels carefully
• Never return unused chemicals to containers
• Dispose of chemicals properly
• Know location of safety equipment

Hazard Symbols

Scientific Notation

Used to express very large or small numbers:

Format: a × 10ⁿ (where 1 ≤ a < 10)

✏️ Worked Examples

Example 1: Significant Figures

Question: How many significant figures in 0.0250?

Step 1 — Know the significant figures rules. Significant figures (sig figs) tell you how precisely a number is measured. The rules:

1. All non-zero digits (1-9) are ALWAYS significant.
2. Zeros BETWEEN non-zero digits are significant (e.g., 101 → the middle 0 is significant).
3. LEADING zeros (zeros before any non-zero digit) are NOT significant — they're just placeholders.
4. TRAILING zeros AFTER a decimal point ARE significant — they show precision.

Step 2 — Apply to 0.0250. Identify each digit:

• "0." → leading zero. Not significant.
• "0" (second zero) → also a leading zero. Not significant.
• "2" → non-zero digit. Significant. ✓
• "5" → non-zero digit. Significant. ✓
• "0" → trailing zero AFTER a decimal point. This tells us the measurement was precise enough to know this digit is zero. Significant. ✓

Step 3 — Count. Three significant digits: 2, 5, and the trailing 0.

Answer: 3 significant figures (the 2, the 5, and the trailing 0 after the decimal).

Why does this matter? In nursing, precision matters. If a drug concentration is 0.0250 mg/mL, the trailing zero is there for a reason — it tells you the concentration was measured precisely to 4 decimal places, not rounded. Dropping significant figures can mean dosing errors.