Elements and Compounds — CHEMISTRY STD 7 — Question

Name the main metal present in the following:
Chlorophyll

Name the polyatomic ion that carries a positive charge.

What kind of valency do the metals generally have?

Answer the question put against the following constituents of air :
Water vapours : Explain their role in modifying the earth’s climate.

State one use of helium

State whether the following is physical or chemical changes.
burning of wood -

State four conditions necessary for chemical reactions to take place.

Write your observation for the following chemical reaction and name the product formed :
When manganese dioxide is added to potassium chlorate and heated.

Name the smallest particle from which matter is made up.

By giving an example define endothermic reaction.