Pins on a metal strip
Set this up and predict first.
Four pins are stuck along a metal strip with wax. Heat the far end with a candle and watch. Which drops first, and do they all drop together?
📚 Chapter Learning Kit
Heat Transfer in Nature · Class 7 Science · Curiosity
English 4 topics 140 leveled MCQs 68 flashcards 5 games Free
Shared by a Veda teacher · Generated with Veda AI · Oct 2026
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They fall in sequence
The order is the finding.
The pin nearest the flame goes first, then the next, and so on. A row falling in order tells you something one pin could not.
Why a pin drops
The wax is the reporter.
Wax melts once it is warm enough, and a pin cannot hang on without it. Each pin dropping marks the moment the warmth reached that spot.
Why smoke goes up
Start with a question.
Nobody pushes the smoke from a wood fire, and it climbs anyway. The answer to that is the whole of this topic.
The stick tips
Two cups on a stick.
Hang two paper cups upside down from a level stick and put a candle under one. That cup lifts, so the air above the candle must be rising and pushing it.
Switch to water
Air is hard to watch.
Put a beaker of water over a candle and feed in a streak of coloured water near the bottom. Now the moving stuff has a colour and you can follow it.
📖 Smart notes
What you'll study, topic by topic
1
Conduction of Heat
Heat travels along a metal strip and makes pins drop one after another. That hand-to-hand passing is conduction, and it explains everything from cooking pots to woollen jumpers.
- Heat travels from the hotter part of an object towards the colder part.
- That hand-to-hand passing of heat is called conduction.
- A heated particle passes heat to its neighbour, but does not move itself.
~40 min · full explanation, examples & memory tricks in the app
2
Convection, and the Breeze off the Sea
Warm water rises, cool water sinks, and the whole beaker heats itself by going round. The same circling air is why the wind at the seaside blows one way by day and the other by night.
- A coloured streak in a heated beaker rises up the middle and comes down the sides.
- Water at the bottom gets hot, expands, becomes lighter and rises.
- Cooler, heavier water from the sides sinks to take its place.
~45 min · full explanation, examples & memory tricks in the app
3
Radiation, and All Three at Once
The Sun warms you across empty space, which neither of the other two methods could manage. Then a single pan of water on a flame turns out to use all three at the same time.
- Sitting near a fire you feel warm because heat comes straight to you.
- That direct transfer from a hot object is called radiation.
- Radiation needs no medium at all to travel through.
~40 min · full explanation, examples & memory tricks in the app
4
The Water Cycle, and Water Under the Ground
The Sun lifts water into the air and it comes back as rain, which is a loop that never finishes. Some of the returning water soaks down and waits underground, where we go to find it.
- Water is found in nature as a liquid, as a solid and as a gas.
- The Sun radiation melts mountain snow in summer, feeding the rivers.
- Water evaporates from oceans, rivers and lakes, and from plants by transpiration, and the rising vapour then condenses into clouds.
~50 min · full explanation, examples & memory tricks in the app
❓ Leveled MCQ practice
Try the smart MCQs from this kit
140 questions laddered from warm-up to topper-level, each with an explanation. A taste:
The pins are stuck along the metal strip with wax and the candle is lit at one end of it. The pin that drops first is the one
Beginner
A furthest from the candle flame
B exactly in the middle of it
C nearest to the candle flame
D held by the largest wax blob
Show answer & explanation
nearest to the candle flame
The warmth reaches the nearest spot first and melts that wax first.
The pins fall one after another rather than together because
Beginner
A heat takes time to travel along
B the wax blobs were of noticeably different sizes to begin with
C the pins have different weights
D the strip bends as it warms
Show answer & explanation
heat takes time to travel along
Heat works along the strip, so it arrives at each spot in turn.
The experiment would work just as well with a glue that melts at the same temperature as wax. What job does the wax actually do?
Intermediate
A It carries the heat along the metal strip from one pin to the next
B It keeps the metal strip from becoming too hot to touch safely
C It holds the pins only
D It reports where the heat has reached
Show answer & explanation
It reports where the heat has reached
The wax melts once warm, so each dropping pin marks the heat arrival.
Warmth working its way from a warmer part of a thing towards a cooler part is
Beginner
A convection
B conduction
C radiation
D insulation
Show answer & explanation
conduction
That is exactly what the word conduction names.
🃏 Flashcards
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68 flashcards in this kit — the app reviews them with spaced repetition so the right card returns on the right day.
🎮 Learning games
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Fact Or Myth
Sequence Builder
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Speed Quiz
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