Here you will get the CBSE Class 10 Science Practice Paper 2017-2018: Set-I, to prepare for the class 10 Board Exams 2018. This practice paper has been designed as per the new examimation pattern that covers the complete syllabus of CBSE Class 10 Science.
All the questions in CBSE Class 10 Science Solved Practice Paper : Set-I have been asked from the most important topics of class 10 Science. Practicing this paper will help you know your weak areas which you need to revise to fine-tune your praparations. This way you may access your preparedness for the exam.
Some of the sample questions from CBSE Class 10 Science Solved Practice Paper : Set-II are given below:
Q. Explain what is galvanisation. What purpose is served by it?
The process of coating the iron objects by zinc metal is called galvanisation.
Galvanisation is used to prevent rusting of iron.
Q. All the variations in a species do not have equal chances of survival. Why ?
All the variations in the species do not have equal chances of survival in the environment. The variations most adapted to environmental conditions and factors will survive. Selection of variants by environmental factors forms the basis for evolutionary processes.These variations may lead to increased survival advantages of the individuals due to positive adoption of traits or may merely contribute to the genetic drift. For example, among a population of red beetles there were some green bettles produced due to variation. Most of the red beetle started vanishing because they were eaten up by crows as they were visible in green bushes. Whereas green beetles were not eaten by crows and other predators as their body color was same as that of the bushes. Thus green color of beetles saved them from predators thus providing a survival advantage. This phenomenon is also known as Natural selection.
Q. (a) A mixture of ethyne and pure oxygen is used for welding instead of using a mixture of ethyne and air. Why?
(b)Why pure acetic acid is called glacial acetic acid?
(a) Ethyne is an unsaturated carbon compound. It burns in air with a sooty flame. It’s an incomplete combustion since the oxygen available from air is not enough to burn the carbon completely. Therefore, for complete combustion pure oxygen is required, which burns Carbon and Hydrogen completely producing a very hot and clean flame apt for welding. It is not possible to generate such a high temperature without pure oxygen.
(b) The Freezing point of pure acetic acid is very high. It freezes into a solid at a temperature very close to room temperature: 16.5 ºC, or 62 ºF. Hence, during winters it gets frozen due to cold climate and appears like an ice. That is why pure acetic acid is called glacial acetic acid.
Q. Explain how equal genetic contribution of male and female parents is ensured in the progeny.
In human beings, equal genetic contribution of male and female parents is ensured in the progeny through inheritance of equal number of chromosomes from both parents. There are 23 pairs of chromosomes All human chromosomes are not paired. Out of these 23 pairs, the first 22 pairs are known as autosomes and the remaining one pair is known as sex chromosomes represented as X and Y. Females have a perfect pair of two X sex chromosomes and males have a mismatched pair of one X and one Y sex chromosome.
During the course of reproduction, as fertilization process takes place, the male gamete (haploid) fuses with the female gamete(haploid) resulting in formation of the diploid zygote. The zygote in the progeny receive an equal contribution of genetic material from the parents. Out of 23 pairs of chromosomes in progeny, male parent contributes 22 autosomes and one X or Y chromosome and female parent contributes 22 autosomes and one X chromosome
Q. A student adds a spoon full of powdered sodium hydrogen carbonate to a flask containing ethanoic acid. List two main observations that he/she must note in his/her notebook about the reaction that takes place. Also, write chemical equation for the reaction.
Two important observations that must be noted when student adds a spoon full of powdered sodium hydrogen carbonate to a flask containing ethanoic acid are:
1. Brisk effervescence is observed due to the release of CO from the reacting mixture.
2. Heat is released during the reaction.
Chemical equations for the reaction are:
NaHCO3 + CH3COOH → CH3COONa + CO2(g) + H2O
Ca(OH)2 + CO2 → CaCO3 + H2O
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