Question

16 Which change results in the formation of different substances?(1) burning of propane

(2) melting of NaCl (s)
(3) deposition of CO2(g)
(4) solidification of water

Answer 1

1. The burning of propane creates different substances: propane and oxygen combine to create water and carbon dioxide:

C3H8 + 5 O2 becomes 3 CO2 + 4 H2O + heat

2. When NaCl melts, it is changing state, but it is still the same NaCl.

3. When gaseous CO2 deposits it is changing state, but it is still the same CO2.

4. When (presumably liquid) water solidifies, it is changing state, but it is still the same water.

So the answer is 1.

Answer 2

Answer:The correct answer is option (1).

Step-by-step explanation:

Burning of propane in the presence of oxygen will form carbon-dioxide, water and heat.The chemical reaction can represented as in chemical equation:

`C_3H_8+5O_2\rightarrow 3CO_2+4H_2O+heat`

This is an example of chemical change where new product is formed.

Where as in melting of sold sodium chloride, deposition of carbon-dioxide gas and solidification of water ;phase of the substance is changing that is a physical change is taking place.

Hence, the correct option is (1).