What are the possible changes occur during a chemical reaction?

Q. (a) What is meant by chemical reaction? Explain with the help of an example.
(b) Give one example each of a chemical reaction characterised by:
(i) evolution of a gas
(ii) change in colour
(iii) formation of a precipitate
(iv) change in temperature
(v) change in state.

Q.

Write the chemical reaction where the following changes are observed.

(a) Gas is evolved

(b) Colour change is noticed

(c) Precipitate is formed

(d) Physical state is changed

Q.

The chemical reaction between quicklime and water is characterised by :
(a) evolution of hydrogen gas

(b) formation of slaked lime precipitate

(c) change in temperature of mixture

(d) change in colour of the product

Q. Assertion :"A golden yellow precipitate of lead iodide is formed when colourless lead nitrate solution is mixed with colourless solution of potassium iodide." So, it is a chemical change Reason: Formation of new products in the reaction with the precipitate indicates a chemical change

Q.

One of the following does not happen during a chemical reaction. This is :

(a) Breaking of old chemical bonds and formation of new chemical bonds

(b) Formation of new substances with entirely different properties

(c) Atoms of one element change into those of another element to form new products.

(d) A rearrangement of atoms takes place to form new products.