10 Science Solved Sample Paper 3 – Page 3
Question: 10. Name three different glands associated with the digestive system in humans. Also name their secretions. 
Answer: These glands and their secretions are:
- Salivary gland: Its secretion is Saliva
- Liver: It secretion is called Bile juice
- Pancreas: Its secretion is Pancreatic juice.
Explain the ways in which glucose is broken down in absence of oxygen.
Question: 11. Explain why the clear sky appears blue to person on the surface of the earth and dark instead of blue to the passengers flying at very high altitudes. 
Question: 12. A convex mirror used for rear view on an automobile has a radius of curvature of 2 m. If a truck is located at 5 m from the mirror, find the position, nature and size (magnified or diminished) of the image. 
Answer: Convex mirror, R = 2 m ⇒ f = 2/2 = +1 m; u = -5 m, v = ?
1/v + 1/u = 1/f ⇒ 1/v = 1/f – 1/u ⇒ 1/v = 1/1 – 1/-5
⇒ 1/v = 5+1/5 = 6/5 ∴ v = 5/6 = 0.8 m.
⇒ m = –v/u = -0.8/-5.0 = 0.16 (image is erect, virtual and diminished)
Question: 13. What is a wind mill? Write two advantages and two limitations of using wind mills to generate electricity. 
Answer: Wind mill is a device which uses the wind energy (kinetic energy of wind) to generate electrical energy.
Question: 14. The electronic configuration of an element ‘X’ is 2, 8, 8, 2.
Write its (1). group number, (2). period number and (3). the number of valence electrons in its atom. Justify your answer in each case. 
Answer: X = 2, 8, 8, 2 ⇒ (1). Group number = 2nd; (2). Period number = 4; (3). Valence electrons = 2
An element ‘X’ has atomic number 6. Another element ‘Y’ has 17 electrons in its neutral atom.
(1). To which group of modern periodic table do ‘X’ and ‘Y’ belong?
(2). What type of bond will be formed in the compound when ‘X’ and ‘Y’ combine?
(3). Write the formula of this compound. State reason for your answer in each case.
Answer: X = 2, 4; Y = 2, 8, 7
- X belongs to 4th group, Y belongs to 7th group;
- Covalent bond;
Question: 15. Mendel crossed a tall pea plant producing round seeds and a short pea plant producing wrinkled seeds. Write the plant type of F1 and F2 progenies he got and the plant conclusion he had drawn from such a cross.
Hint: Law of Independent Assortment and Dihybrid Inheritance.
F1: all plants were tall with round seeds.
Question: 16. State Ohm’s law. How can it be verified experimentally? Explain with the help of a circuit diagram. Express the result graphically. 
Question: 17. (1). Name the gas which is liberated when an acid reacts with a metal? How will you test the presence of this gas?
(2). Write the chemical equation for the reaction of zinc metal with (i). Hydrochloric acid and (ii). with sodium hydroxide. Write the chemical name of salt obtained in each case.
(3). Identify the acid and base for ammonium chloride salt. What would be the nature of this salt? Mention the pH range of this salt.
- H2 gas; This gas burns with a pop sound.
- (i). Zn + 2HCl → ZnCl2(Zinc chloride) + H2↑
(ii). Zn + 2NaOH → Na2ZnO2(Sodium zincate) + H2↑
- Acid is Hydrochloric acid (HCl); Base is Ammonium hydroxide (NH4OH). This salt is acidic salt as it is a salt of strong acid and a weak base; pH of this salt < 7.