The Language of Chemistry — CHEMISTRY STD 9 — Question

Explain why:
Air dissolved in water contains a higher proportion of oxygen.

The atomic number and mass number of sodium are 11 and 23 respectively. What information is conveyed by this statement?

Give four examples of a chemical change

Identify the gases from the observations:
A colourless and odourless gas, which is neutral towards litmus. It explodes with a ‘pop” sound when a burning wooden splint is held near it.

The table below shows the elements from P to T, such that a pair of elements is an isotope. Identity the pair and give a reason for your choice:

Elements	No. of protons	No. of neutrons	No. of electrons
P	11	12	11
Q	12	12	12
R	11	13	11
S	13	14	13
T	14	14	14

Give the name of the element and number of atom of those elements present in the following compound.
Ammonium dichromate

Which metal is preferred for collecting hydrogen from:
Write the balanced equation
Steam

Give an example of a reaction where the following is involved .
Evolution of heat

What is the nature of the charge on Cathode rays .