Structure of the Atom — Science STD 9 — Question

An element B shows valencies of 4 and 6. Write the formulae of its two oxides.

What are the advantages of composite fish culture?

Which law states, that in a chemical compound, elements always combine in a fixed proportion?

Name the different types of elements found in the xylem.

What is electron microscope?

A boy tries to push a truck parked on the roadside.The truck does not move at all. Another boy pushes a bicycle moves through a certain distance. In which case was the work done more: on the truck or on the bicycle? Give a reason to support your answer.

Compare an electron and a proton in respect of mass and charge.

A body floats in kerosene of density 0.8 × 10³ kg/m³ up to a certain mark. If the same body is placed in water of density 1.0 × 10³kg/m³, will it sink more or less? Give reason for your answer.