Class 7 Science (CTET Paper 2)Critical (2–3 MCQs guaranteed)9 min read
Chapter 4: Heat and Temperature Transfer
ऊष्मा एवं ताप संचरण (चालन, संवहन, विकिरण, नैदानिक थर्मामीटर एवं समुद्री/थल समीर)
CTET Theme: Thermal Physics & Heat Transmission
CTET Medium / परीक्षा माध्यम:Toggle authentic CBSE terminology
CTET On-the-Go Audio NotesHands-Free Revision
Listen to high-yield NCERT facts & CBSE traps without staring at the screen
OVERVIEW1 of 16
Introduction: Heat and Temperature Transfer
Welcome to Mentora CTET Audio Masterclass for Class 7 Science (CTET Paper 2), Chapter 4: Heat and Temperature Transfer. Here are the high-yield facts tested in CBSE examinations.
Aspirant Revision Toolkit:Offline cheatsheet, OMR practice & peer sharing
Offline Pen-and-Paper Exam Readiness
Don't Let a 20-Minute Bubbling Delay Cost You CTET Qualification
In offline CTET exams, bubbling 150 bubbles takes 18 to 22 minutes of mechanical time. A single misaligned row can trigger an 8-question domino error. Practice bubble-filling this chapter's solved MCQs inside Mentora's official OMR simulator.
150-Question CBSE Specimen Grid
Real-time Row-Shift Detection
Printable Official A4 Specimen
High-Weightage NCERT Facts & Key Terms (द्विभाषी)
12 Core Points- Temperature: Quantitative measure of degree of hotness or coldness of an object, measured in degrees Celsius (°C) or Fahrenheit (°F).
- Thermometer Comparison (Guaranteed CTET Question):
- - Clinical Thermometer (नैदानिक थर्मामीटर): Range is 35°C to 42°C (Normal human body temperature is 37°C / 98.6°F). Contains mercury and a distinctive KINK (constriction / विभंग) just above the bulb. The kink prevents mercury from falling back automatically, allowing the doctor to read temperature accurately after removing from mouth.
- - Laboratory Thermometer (प्रयोगशाला थर्मामीटर): Range is -10°C to 110°C. Has NO kink; reading must be noted while bulb remains immersed in the test substance.
- Modes of Heat Transfer:
- - Conduction (चालन): Transfer of heat from hotter to colder end through direct molecular vibration without bulk movement of the medium itself. Dominant in SOLIDS. Good conductors: Copper, Aluminium, Iron. Insulators (poor conductors): Wood, plastic, glass, air, water.
- - Convection (संवहन): Transfer of heat in FLUIDS (liquids and gases) via actual mass movement of heated particles rising (lower density) and cold particles sinking to take their place.
- - Radiation (विकिरण): Transfer of heat via electromagnetic waves without needing any material medium. Can travel across a vacuum (e.g. Solar heat reaching Earth; heat emitted by an incandescent bulb or room heater).
- Coastal Wind Cycles:
- - Sea Breeze (समुद्री समीर): Happens during the DAY. Land warms faster than sea $ ightarrow$ Warm air above land rises $ ightarrow$ Cool air from over sea blows towards land.
- - Land Breeze (थल समीर): Happens during the NIGHT. Land cools down much faster than sea $ ightarrow$ Warm air above sea rises $ ightarrow$ Cool air from land blows towards the sea.
- Thermal Radiation & Color: Dark surfaces absorb more radiant heat (ideal for winter clothes and solar cooker interiors); light/white surfaces reflect radiation (ideal for summer clothes). Woolen garments trap air inside pores; air is a poor conductor of heat, preventing body heat escape.
CBSE Distractor Traps (Avoid Negative Marking)
- Trap: Can a laboratory thermometer be used to measure body temperature? NO, because it lacks a kink; the mercury thread falls immediately upon exposure to room air.
- Trap: Sea breeze blows during the NIGHT. FALSE: Sea breeze blows during the DAY, land breeze blows at NIGHT.
- Trap: Why do two thin blankets keep you warmer than one single thick blanket of equal mass? Correct: Because a layer of air is trapped between the two thin blankets, and trapped air is a poor conductor of heat.
NCERT Core Facts: Thermometry & Heat Transfer Mechanics
Thermal physics questions in CTET Paper 2 focus on thermometer differences and coastal wind mechanisms:
1. Clinical vs. Laboratory Thermometer
| Characteristic | Clinical Thermometer (डॉक्टरी) | Laboratory Thermometer (प्रयोगशाला) |
|---|---|---|
| Operational Range | $35^circ ext{C}$ to $42^circ ext{C}$ | $-10^circ ext{C}$ to $110^circ ext{C}$ |
| Presence of Kink (विभंग) | YES, prevents mercury descent | NO kink; reading drops instantly on removal |
| Reading Procedure | Read after removing from mouth | Read while bulb is still immersed in liquid |
| Normal Human Baseline | $37.0^circ ext{C}$ (98.6^circ ext{F}) | N/A (calibrated for experimental liquids) |
2. Sea Breeze vs. Land Breeze Cycle
DAY TIME: SEA BREEZE (समुद्री समीर)
Sun heats Land faster ──> Warm air rises over Land
▲ │
│ (Breeze In) ▼
Cool Sea Water <──────────────── Cool air pushes in from sea
NIGHT TIME: LAND BREEZE (थल समीर)
Land cools faster ──> Sea stays warmer ──> Warm air rises over Sea
than ocean water ▲ │
│ ▼ (Breeze Out)
Cool air pushes out from Land ─────────────────────┘3. The Three Heat Transfer Pathways
- 1.Conduction (चालन): Solid metal spoon handle heating up in hot soup.
- 2.Convection (संवहन): Water boiling in a pot (hot water rises from base, cold water sinks), coastal wind currents, chimney smoke ascent.
- 3.Radiation (विकिरण): Feeling warmth standing 3 meters from a campfire or fireplace; solar heat crossing 150 million km through vacuum.
Official CTET Benchmark Test
Test Your Mastery: Heat and Temperature Transfer
Authentic CBSE exam questions tested directly from this NCERT chapter.
Question 1 of 2(CTET Jan 2021 & Aug 2023)
A laboratory thermometer cannot be used reliably to measure a patient's body temperature because:
एक मरीज के शरीर के तापमान को मापने के लिए प्रयोगशाला थर्मामीटर का विश्वसनीय रूप से उपयोग नहीं किया जा सकता क्योंकि:
Question 2 of 2(CTET Dec 2019)
Why are two thin blankets of combined thickness T found to be warmer than a single thick blanket of identical thickness T?
समान मोटाई T के एक मोटे कंबल की तुलना में कुल मोटाई T के दो पतले कंबल अधिक गर्म क्यों महसूस होते हैं?
Mastered this chapter? Practice under genuine 150-minute exam conditions.
Open Full OMR SimulatorFrequently Asked Questions (CTET Pedagogy)
What is the specific function of the kink in a clinical thermometer?
The kink (constriction) prevents the column of mercury from falling down on its own when the thermometer is taken out of the patient's mouth.
Why does sea breeze blow during daytime in coastal zones?
During daytime, land absorbs heat faster than sea water. The warm air above land rises, creating a low-pressure area that pulls cooler air from over the sea towards land.