Heat Transfer in Nature: questions with answers

The transfer of heat here takes place from the hot end of the strip to the colder end. As the heat travels along the strip and approaches a pin, the wax holding it melts and the pin falls. The pin nearest the flame is reached first, so its wax melts first.

Heating spreads from the hot end towards colder parts. With comparable wax amounts, the nearest pin is released first, followed by progressively more distant pins.

Still air between two tumblers slows heat transfer because air is a poor conductor. It reduces heat entering the cold lassi from warmer surroundings, so the lassi stays cold longer. Insulation slows warming; it does not make the lassi colder than it was initially.

The water nearest the flame is heated first. It expands, becomes lighter than the water around it, and therefore rises straight up from the place where it was heated. The cooler, heavier water elsewhere in the beaker then comes down to take its place, and the cycle continues until the entire volume of water gets heated.

Each candle heats the water at the bottom of its tube first. That water expands, becomes lighter and rises. Cooler, heavier water comes down to take its place. This cycle goes on until the whole volume of water is heated. Shortly after the candles are lit, the water is not equally hot throughout. The bulb sitting nearer the flame therefore records the higher temperature.

Air heated by the candle expands, becomes less dense and rises. The upward airflow lifts the cup above the candle and disturbs the balance.

Radiation needs no material, so it still crosses the empty gap. Convection needs moving air or water, and none is left in the gap.

The utensil and room both emit thermal radiation. The hotter utensil emits more radiation energy than it absorbs, contributing to its cooling.

A daytime sea breeze comes from the sea. A night-time land breeze comes from the land. The name identifies the source of the moving air.

Under the comparable conditions of this activity, soil warms more than water. The bowl with the higher thermometer reading therefore contains soil.

Land warms faster than the sea during the day. Air rises over the warmer land, and cooler sea air moves inland through sea-facing openings.

An arrow rising from a water surface is evaporation; an arrow rising from trees and plants is transpiration; an arrow falling from a cloud is precipitation. Condensation is not an arrow at all: it is what happens inside the cloud when the risen vapour cools.

Some rainwater flows over the surface into streams and other water bodies. Some enters connected spaces in soil and rock and can replenish groundwater.

Water seeps fastest through gravel, slower through sand, and slowest through clay, because the spaces between gravel particles are wider than those in sand and clay. The bottle holding the gravel therefore lets the most water through in the same time.

The process of surface water seeping through soil and rocks is called infiltration. Groundwater is not the process but its result. It is the water that seeps down and is stored in the pore spaces of sediments and in the openings in rocks.