Name (a) three elements that have a s | 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?

How can we explain the reddish appearance of sun at sunrise or sunset? Why does it not appear red at noon?

How are fats digested in our bodies? Where does this process take place?

Give an example of a metal which

  (i) is a liquid at room temperature.
  (ii) can be easily cut with a knife.
  (iii) is the best conductor of heat.
  (iv) is a poor conductor of heat.

Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.

Why does absorption of digested food occur mainly in the small intestine?

Which of the following terms does not represent electrical power in a circuit?

(a) I²R          (b) IR²          (c) VI          (d) V²/R

Identify the substances that are oxidised and the substance that are reduced in the following reactions.

    (i)    4Na(s)   +   O₂(g)    →    2Na₂O(s)
    (ii)   CuO(s)   +   H₂(g)    →    Cu(s)   +   H₂O(l)

Distinguish between a gamete and zygote. Explain their roles in sexual reproduction.

Why are some substances biodegradable and some non-biodegradable?

What are the environmental consequences of using fossil fuels?
Suggest the steps to minimise the pollution caused by various sources of energy including non-conventional sources of energy.