Category Everyday Science

Glass is a bad conductor of heat. If a glass vessel is heated directly over a flame, the heat is not readily conducted to other parts of the vessel and even at the point of contact with the flame, the inside surface does not get as hot as the outside surface.

Consequently the outside surface expands more than the inside surface and the unequal expansions cause the glass to crack.

To avoid this the glass vessel is usually heated by keeping it on a wire gauze made of a good conductor of heat such as iron or copper. This ensures that heat is transferred indirectly and slowly to the glass vessel and the vessel does not crack.

Picture Credit : Google

The ink is stored in the barrel of the pen. When we start writing, the ink flows down and collects at the hole near the middle of the nib. When we press the nib against the paper while writing, the slit in the nib opens slightly and behaves as a very narrow tube or capillary. The ink is pulled through the tube by capillary force and flows onto the paper through the tip of the nib.

Why isn’t it possible to write on an extremely smooth surface with a ballpoint pen?

The tip of the ballpoint pen consists of a small ball which projects from a metallic socket. Fast-drying, oil-based ink is supplied to it through a narrow tube. When we write, the ball rotates and transfers the ink onto the paper. If the surface on which we want to write is very smooth, there will not roll efficiently. Consequently the ink will not get transferred to the paper. Sometimes, the ball may be rotating but the ink may not be able to adhere to the surface.

Picture Credit : Google

The speed of sound in air varies. At sea level it is about 1220 kmph but at higher altitudes, where air is cooler, it slows down becoming about 1,070 kmph at a height of 11,000 metres. Because the speed of sound changes with height, planes that fly faster than the speed of sound use a Mach number to measure their speed. The Mach number is the aeroplane’s speed divided by the speed of sound at the height the aeroplane is flying.

Mach 2 indicates a speed of twice the speed of sound. At Mach 1 the plane is flying at the speed of sound. Mach 0.5 is half the speed of sound, or subsonic.

Many fighter aircraft are capable of flying at high Mach numbers.

The unit is named after Ernst Mach, an Austrian physicist.

Picture Credit : Google

The freezing of water starts at the walls of the tray and at the open surface as these are the areas in contact with a cooler material. As water is a bad conductor, the cooling process of freezing moves from outside to the inside. Water has some air dissolved in it. These air molecules occupy the spaces between the water molecules. When the water starts freezing, i.e. when liquid water changes to solid state, the air molecules are forced out from the inter-molecular spaces. They can now move only to the interior where some liquid still exists. As finally, the whole volume of water freezes, the air molecules get trapped in the middle as tiny bubbles. It is these air bubbles that make the centre of the ice cube opaque. The rest of the cube, being pure ice, is transparent.

Picture Credit : Google

Electricity resulting from the application of mechanical pressure on certain crystals like quartz and tourmaline is called piezoelectricity.

When these crystals are subjected to mechanical strain, a voltage across their opposite faces.

Conversely when a voltage is applied to such crystals, they vibrate.

Piezoelectric materials are used for converting mechanical strain into an electrical signal in such devices as microphones and phonograph pick-ups. The converse effect in which a mechanical output is derived from an electrical signal output is used in such devices as headphones and quartz watches.

The phenomenon of piezoelectricity was discovered in the 1880s.

Picture Credit : Google

When reading the printed matter on the wrapper of a bar of toilet soap, I saw the following: TFM = 75% written in bold letters.

What is the meaning of TFM and what is its significance?

The chief ingredients of soap are fats – manufacturers either use animals fats or a vegetable oil, like coconut oil – and an alkali, usually caustic soda. The fats are the most important part of the soap.

TFM stands for Total Fatty Matter. This expresses the real soap content in the toilet soap. If TFM is given as 75% it means that the actual soap content is 75%, while the remaining portion consists of additives, which make it foam, or give it its colour, or keep it hard.

The higher the TFM percentage, the better is the quality of the soap. It is binding on the manufacturer to state how much fatty material there is in the soap.

Picture Credit : Google