Is Matter Around Us Pure — Science STD 9 — Question

What is a chemical change?
Give two examples of chemical changes.

Atom A has a mass number 209 and atomic number 82.
Atom B has a mass number 209 and atomic number 83.

1. How many protons atom A has?
2. How many protons atom B has?
3. Are atoms A and B isotopes of the same element?

The mass of one steel screw is 4.11g. Find the mass of one mole of these steel screws. Compare this value with the mass of the earth (5.98 × 10²⁴kg). Which one of the two is heavier and by how many times?

Define ‘melting point’ of a substance? What is the melting point of ice?

Which ancient Indian philosopher suggested that all matter is composed of very small particles? What name was given by him to these particles?

The solubility of ammonium chloride in water at various temperatures is given below:

Temperature:	10°C	20°C	40°C	60°C	80°C
Solubility:	24g	37g	41g	55g	66g

What mass of ammonium chloride whould be needed to make a saturated solution of ammonium chloride in fifty grams of water at 40°C?

Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3g of hydrogen gas?

Predict the mass possessed by certain number of oxygen atoms which is equal to the number of molecules present 1g of hydrogen gas?

Calculate the volume by volume percent solution formed by combining 18ml of pure hydrogen peroxide with water to make 630ml of solution.

Classify the following into metals, non-metals and metalloids:
Silicon, Mercury, Diamond, Sulphur, Iodine, Germanium, Sodium, Carbon, Magnesium, Copper, Boron, Helium.