(a) Lithium, sodium, potassium are all m | Class 10 Science Chapter Periodic Classification of Element, Periodic Classification of Element NCERT Solutions

When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.

Outline a project which aims to find the dominant coat colour in dogs.

Draw the structure for the following compounds.                

       (i)    Ethanoic acid             (ii)   Bromopentane*
       (iii)  Butanone                   (iv)   Hexanal.

*Are structural isomers possible for bromopentane?

A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?

How is the sex of the child determined in human beings?

(a)  What property do all elements in the same column of the Periodic Table as boron have in common?
(b)  What property do all elements in the same column of the Periodic Table as fluorine have in common?

Calculate the number of electrons constituting one coulomb of charge.

A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?

What is an homologous series? Explain with an example.

Why is variation beneficial to the species but not necessarily for the individual?

Explain the nature of the covalent bond using the bond formation in CH₃Cl.

What are the limitations in obtaining energy from wind?

What are the different ways in which individuals with a particular trait may increase in a population?

How much energy is given to each coulomb of charge passing through a 6 V battery?

Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

Give reasons why acquired characters are not inherited.

Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?

How does fertilisation take place? Fertilisation occurs once in a month. Comment.

What are amphoteric oxides? Give two examples of amphoteric oxides.