🔧 Master Modal Verbs
2nd Year BAC Sciences Physiques SPC
📌 Introduction
Modal verbs are auxiliary verbs that express necessity, possibility, permission, or ability. They are essential for scientific discussions and lab reports.
Key Features
- No -s in third person
- No infinitive form
- Followed by base verb
- Express modality
Common Modals
Science Tip: “85% of lab safety instructions use modal verbs like ‘must’, ‘should’, and ‘may not’.”
🔍 Core Modal Verbs in Science
| Modal | Function | Example |
|---|---|---|
| Must | Obligation/necessity | “You must wear goggles” |
| Should | Recommendation | “We should repeat the test” |
| Can | Ability/Possibility | “This solution can dissolve metals” |
| May/Might | Uncertainty | “The reaction may produce gas” |
| Must not | Prohibition | “You must not mix these chemicals” |
🎯 Exercise: Function Matching
Match each modal to its primary scientific function:
1. Must
2. Can
3. May
📊 Degrees of Certainty
Scientific Probability Scale:
100% Certain: “Water must boil at 100°C at sea level”
80-90%: “This should give accurate results”
50%: “The compound may crystallize”
30-40%: “We might observe precipitation”
Negative Certainty: “That can’t be pure” (100% negative)
Weak Negative: “It might not react” (possible negative)
🔢 Exercise: Probability Ranking
Order these statements from most (1) to least (4) certain:
🧪 Lab Context Practice
Common Lab Scenarios
- “You must wear protective equipment at all times.” (obligation)
- “This substance can cause burns.” (potential)
- “We should record all observations immediately.” (recommendation)
- “The mixture might change color.” (uncertainty)
⚠️ Exercise: Safety Instructions
Complete these lab safety rules with appropriate modals:
1. “Students wash hands after experiments.”
2. “You eat in the laboratory.”
3. “Unknown substances be toxic.”
⏳ Past Forms of Modals
Present → Past
- can → could
- may → might
- must → had to
- should → (no change)
Examples
“We could see the results”
“They had to evacuate”
🕰️ Exercise: Past Tense Conversion
Rewrite these sentences in past tense:
1. “She can analyze the data quickly.” →
2. “We must follow the protocol.” →
📝 Writing Practice
✍️ Exercise: Lab Report
Write 3 sentences about an experiment using these modals:
