PART - 2 CH - 5 Life processes — Science STD 10 — Question

Do these elements also contain the same number of valence electrons?

State the minimum number of carbon atoms required to form the ring structure.

Name the sodium compound which is used for softening hard water.

Define the term : Bud

Define magnetic field.

Which metals will melt, if you keep them on your palm?

Define term : Hydrocarbons

Which lens is used as a magnifying lens?

An eye camp was organised by the doctors in a village. They found that the eyes of aged people in the village have the near point receded and the far point also gets reduced. Often aged people suffer from both myopia and hypermetropia. Doctors (opthalmologists) provide these people spectacles of bi-focal lenses to correct the defects. The people were happy and grateful to the doctors.
(1) Name the eye defect from which the people were suffering.
(2) Give any two causes of this defect.
(3) What were benefits to organise such camps in rural areas? Give two suggestions.

How many elements were known when Mendeleev started the classification of elements?