Improvement In Food Resources — Science STD 9 — Question

Conversion of solid state to liquid state is called fusion; what is meant by latent heat of fusion?

'Milk is a very nutritious food'. Use the table given in the book to justify statement.

Which postulate of Dalton’s atomic theory can explain the law of conservation of mass?

Composition of the nuclei of two atomic species A and B is given as under:

	A	B
Protons	18	20
Neutrons	22	20

Give the mass numbers of A and B. What is the relation between the two species and which element or elements they represent?

A man X goes to the top of a building by a vertical spiral staircase. Another man Y of the same mass goes to the top of the same building by a slanting ladder. Which of the two does more work against gravity and why?

What do you observe in the china dish during crystallization?

Atomic number of aluminium is 13 and mass number is 27. Calculate the number of electrons, protons and neutrons in its atom. Represent the ion of this element.

Compare the use of manure and fertilizers in maintaining soil fertility.