Heredity and Evolution — Science STD 10 — Question

How is the sex of a newborn determined in humans?

i. By the transfer of electrons, illustrate the formation of bond in magnesium chloride and identify the ions present in this compound.
ii. Ionic compounds are solids. Give reasons.
iii. With the help of a labelled diagram show the experimental set up of action of steam on a metal.

What are esters? How are esters prepared? Write the chemical equation for the reaction involved. What happens when an ester reacts with sodium hydroxide? Write the chemical equation for the reaction and also state the name and use of this reaction.

What is Ohm’s law? Explain how it is used to define the unit of resistance.

Why is biogas considered an ideal fuel for domestic use?

Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

A 3 cm tall object is placed 18 cm in front of a concave mirror of focal length 12 cm. At what distance from the mirror should a screen be placed to see a sharp image of the object on the screen. Also calculate the height of the image formed.

Draw ray-diagrams to show the formation of images when the object is placed in front of a concave mirror (converging mirror):

1. Between its pole and focus.
2. Between its centre of curvature and focus Describe the nature, size and position of the image formed in each case.

A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal and its ore and give the reaction involved.

An eye has a near point distance of 0.75m. What sort of lens in spectacles would be bneeded to reduce the near point distance to 0.25m? Also calculate the power of lens required. Is this eye long-sighted or short sighted?