Test: Class 10 General Science NCERT Based - 2 - UPSC MCQ

• Diamond and Graphite are formed by carbon atoms, the difference lies in the manner in which the carbon atoms are bonded to one another. In Diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure.

• In graphite, each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array.

• Fullerenes from another class of carbon allotropes. The first one to be identified was C-60 which has carbon atoms arranged in the shape of a football.

• Sugarcane plants are one of the most efficient convertors of sunlight into chemical energy.

• Sugarcane juice is used to prepare molasses which is fermented to give alcohol (ethanol). Some countries now use alcohol as an additive in petrol since it is a cleaner fuel which gives rise to only carbon dioxide and water on burning in sufficient air (oxygen).

• As the Alcohol molecule contains oxygen, it allows the engine to more completely combust the fuel, resulting in fewer emissions and thereby reducing the occurrence of environmental pollution. Since alcohol is produced from plants that harness the power of the sun, it is also considered as renewable fuel.

• Mendeleev examined the relationship between the atomic masses of the elements and their physical and chemical properties. He observed that most of the elements got a place in a Periodic Table and were arranged in the order of their increasing atomic masses.

• It was also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties. Mendeléev left some gaps in his Periodic Table. Instead of looking upon these gaps as defects, Mendeléev boldly predicted the existence of some elements that had not been discovered at that time.

• Certainly, no fixed position can be given to hydrogen in the Periodic Table. This was the first limitation of Mendeléev’s Periodic Table. He could not assign a correct position to hydrogen in his Table.

• Isotopes were discovered long after Mendeléev had proposed his periodic classification of elements.

• Isotopes of an element have similar chemical properties, but different atomic masses. Thus, isotopes of all elements posed a challenge to Mendeleev’s Periodic Law. Another problem was that the atomic masses do not increase in a regular manner in going from one element to the next. So it was not possible to predict how many elements could be discovered between two elements — especially when we consider the heavier elements.

1. The Modern Periodic Law states: 'Properties of elements are a periodic function of their atomic number'.

2. The atomic number gives us the number of protons in the nucleus of an atom and this number increases by one in going from one element to the next.

3. Elements, when arranged in order of increasing atomic number Z, lead us to the classification known as the Modern Periodic Table. Prediction of properties of elements could be made with more precision when elements were arranged on the basis of increasing atomic number.

4. The Modern Periodic Table has 18 vertical columns known as ‘groups’ and 7 horizontal rows known as ‘periods’.

2. The target organs or the specific tissues on which it acts include the heart. As a result, the heart beats faster, resulting in supply of more oxygen to our muscles.

3. The blood to the digestive system and skin is reduced due to contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles.

4. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the situations like fighting and running.

5. Testosterone and estrogen are the reproductive hormones such animal hormones are part of the endocrine system which constitutes a second way of control and coordination in our body.

2. Growth hormone is one of the hormones secreted by the pituitary. As its name indicates, growth hormone regulates growth and development of the body. If there is a deficiency of this hormone in childhood, it leads to dwarfism.

3. Insulin is the hormone which is produced by the pancreas and helps in regulating blood sugar levels. If it is not secreted in proper amounts, the sugar level in the blood rises causing many harmful effects.

• In anaerobic respiration, there is a lack of oxygen in our muscles. Pyruvate instead of breaking down to form carbon-dioxide and water, it disintegrates into lactic acid and its accumulation in our muscles leads to cramps.

• Aquatic organisms breathe much faster than terrestrial organisms as the amount of oxygen dissolved in water is less as compared to the amount of oxygen in air. To compensate for this, the breathing rate of aquatic organisms is faster.

• The digestion functions are taken care of by the gastric glands present in the wall of the stomach. These release Hydrochloric acid, a protein digesting enzyme called pepsin, and mucus.

• The Hydrochloric acid creates an acidic medium which facilitates the action of the enzyme ‘pepsin’. The mucus protects the inner lining of the stomach from the action of the acid, that causes "acidity" in adults.

• In human beings, air is taken into the body through the nostrils. The air passing through the nostrils is filtered by fine hairs and harmful microbes are trapped. The passage is also lined with mucus which helps in this process.

• Rings of cartilage are present in the throat which ensure that the air passage does not collapse. Once oxygen enters the blood from the lungs, it is taken up by haemoglobin (Hb) in the red blood cells and forms oxyhaemoglobin thereby oxygen gets circulated in the entire body.

• The force that blood exerts against the wall of a vessel is called blood pressure. This pressure is much greater in arteries than in veins as arteries carry oxygenated blood from the heart to other parts of the body that emerge at high pressure and remain the same.

• The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg. Blood pressure is measured with an instrument called sphygmomanometer.

• The DNA in a cell nucleus is an information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs.

• Therefore, a basic event in reproduction is the creation of a DNA copy. Cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell, that will need to be separated from each other. No bio-chemical reaction is absolutely reliable.

• Therefore, it is only to be expected that the process of copying the DNA will have some variations each time. As a result, the DNA copies generated will be similar, but may not be identical to the original.

• A population of organisms fill well-defined places, or niches, in the ecosystem, by using their ability to reproduce. The consistency of DNA copying during reproduction is important for the maintenance of body design features that allows the organism to use that particular niche. Reproduction is therefore linked to the stability of the population of species.

• Stamen is the male reproductive part and it produces pollen grains that are yellowish in colour.

• Carpel is present in the centre of a flower and is the female reproductive part. It is made up of three parts.

• The swollen bottom part is the ovary, the middle elongated part is the style and the terminal part which may be sticky is the stigma. The ovary contains ovules and each ovule has an egg cell.

• The pollen needs to be transferred from the stamen to the stigma. If this transfer of pollen occurs in the same flower, it is referred to as self-pollination. On the other hand, if the pollen is transferred from one flower to another, it is known as cross pollination. This transfer of pollen from one flower to another is achieved by agents like wind, water or animals.

• The formation of germ-cells or sperms takes place in the testes. These are located outside the abdominal cavity in the scrotum because sperm formation requires a lower temperature than the normal body temperature.

• The role of the testes in the secretion of the hormone, testosterone, is to regulate the formation of sperms, and brings about changes in appearance, seen in boys at the time of puberty such as broadening of chest. In adolescent boys, sometimes, the muscles of the growing Voice Box go out of control and the voice becomes hoarse.