My Science School

The severity of an earthquake can be measured either by measuring its magnitude or intensity. Magnitude is a measure of the strength of an earthquake at its source. It is assessed on an 8-point scale called the Richter Scale. Devised in 1935, by an American geophysicist, Charles Richter, the scale assigns a number to an earthquake depending on its strength. The Richter magnitude is calculated by using information obtained from a seismograph — the instrument that records an earthquake’s ground motion.

Intensity is a measure of the local effect caused by an earthquake which varies according to distance from the source of the earthquake. The intensity is measured in the Mercalli scale, formulated originally by an Italian seismologist Giuseppe Mercalli. The scale was subsequently modified and is still used as the Modified Mercalli Intensity Scale (MM). It classifies earthquake into 12 categories ranging from 1 (not felt except by few) to 12 (total destruction).

 

Stars take birth out of clouds of hydrogen, helium and dust particles present in galaxies. Due to the turbulent motion in these gas clouds, the dust particles undergo random collisions and condense under the influence of strong gravitational pull. As the gases and dust particles begin condensing, the temperature inside rises due to increasing pressure. As the condensing mass grows bigger the gravitational pressure at the centre increases further till the intense heat raises the temperature to around 10 million degrees Celsius. At this temperature the hydrogen atoms start colliding so vigorously that they fuse with each other to form helium atoms. In the process some mass is lost. For every 1000 kg of hydrogen used up, 993 kg of helium is formed. The rest is converted into tremendous amount of energy according to the relationship E= , where E is the energy, m the mass and c the velocity of light. This energy is liberated in the form of light and heat and a star is born.

The shine of a surface depends on its smoothness. Smoother the surface, more it will reflect light and thus will appear shiny. Unpolished leather does not shine because its surface is full of tiny pores and is rough. When we apply polish on this rough surface, the wax in the polish fills up the very small microscopic pits of the leather surface. Vigorous brushing or rubbing with a soft cloth spreads the wax evenly by melting. This makes the surface shine. If the shoe is rubbed after a few drops of water is sprinkled on it, it shines even more because the cloth surface after absorbing little water does not stick to the wax on the leather surface but glides smoothly. Liquid shoe polishes do not need rubbing as these leave a quick drying film on the leather which itself is reflecting and gives a glossy look. 

Curd is formed by a chemical reaction which involves casein, the protein that occurs in milk. The coagulation of this protein results in the formation of curd. This occurs if bacteria called Lactobacillus acidophilus is present in milk. This bacterium produces lactic acid by the fermentation of the milk sugar lactose. The lactic acid so formed by the bacterial action contains positive hydrogen ions which are attracted to the negative particles of the protein casein. As the latter are neutralized, these protein molecules no longer repel one another but coagulate. The optimum temperature at which Lactobacillus acts is around 40°C. So milk is usually warmed to this temperature before setting it to curdle. 

The naphthalene balls used for keeping away harmful insects from damaging clothes are basically volatile chemicals having a strong odour. These compounds include a wide variety of aromatic chemicals which are mainly derived from petroleum and coal tar. These chemicals are toxic. As they are highly volatile, they produce vapours which repel insects such as moths and silverfish which damage clothes during storage.

Wool fibres are made of a particular protein (Keratin) which is a bad conductor of heat and as a result does not allow body heat to escape. This helps us in keeping warm during winter. These fibres are wavy in structure, the property commonly known as crimp. Crimp imparts resilience to the fibre due to which fibres quickly recover from wrinkling and crushing. Because of this wavy structure the fibres do not come perfectly close and as a result a large number of air pockets are formed. The air entrapped within these pockets acts as an insulator and traps body heat inside.

Hail is formed in thunder clouds when ice pellets formed near the freezing level in the atmosphere are caught in air currents. They are tossed up and down by air currents within the thundercloud where these pellets collide and fuse with one another. Further deposition of water or ice, causes them to grow into hailstones. Certain conditions such as vertical upward air currents help prevent hail falling too quickly and results in the increase in the size of hailstones.

 

Plants have special structures called root hairs for absorbing water and other nutrients from the soil. The root-hairs are thin-walled extensions of the outer layer of cells in the root. Deep underground they are surrounded by solutions of various minerals and nutrients in the moist soil. Some of these nutrients such as the nitrogen compounds simply pass through the root-walls when they are present in high concentrations in the soil. The process can be likened to the natural flow of water from the high hills to low valleys. Other nutrients such as minerals which are present in lesser quantities in the soil than inside the cells are transported into the root hairs by special proteins located on the cell-walls, a process which can be likened to pumping of water from wells to tanks higher up. 

The annular rings or the alternating dark light circles seen in a cross section of a tree are produced because of differences in the rate of growth in different seasons. As it happens, the entire tissue in the trunk of a tree does not divide or grow to increase the girth of the tree. There is a layer of dividing tissue called the cambium sandwiched between the fibrous xylem (the water carrying tissue) and the phloem (the food carrying tissue). However, the cambium divides at different rates in different seasons. In winter, its growth is slower than in other seasons, say in spring, when conditions for growth are fairly favourable. Thus, the relatively small number of cell produced in winter remain compacted together producing a dark band while the cells produced during the spring season spread out into a broader light band. These growth patterns are repeated at annual intervals and hence the name. The annular rings thus indicate the age of a tree as well as the changes in climate that might have occurred in the tree’s life time.

Cells in the root hairs of plants contain dissolved sugars and salts. Water surrounding the root moves into them to equalize the pressure. This is called osmosis. The increased water pressure in root hairs forces water upward, cell by cell through the roots and trunk to reach the leaves.

In addition to this, during the growing season, a tree passes tonnes of water into the atmosphere from its leaves through transpiration.

This creates a partial vacuum that is quickly filled by the water being pushed up from the roots. Water molecules stick together, and as water is lost during transpiration, this cohesion causes a chain reaction that is transmitted all the way down.