Which of the following statements about physical changes is correct? MCQ with Answer and Explanation

Explanation:
Red litmus turning blue indicates a basic solution, pH > 7. pH 11 is strongly basic. pH 3 and 6 are acidic (blue litmus turns red). pH 7 is neutral (litmus remains purple). Litmus is a common natural indicator.

Explanation:
In water, soap molecules arrange themselves into spherical aggregates called micelles. The hydrophobic hydrocarbon tails point inward, away from water, while the hydrophilic ionic heads point outward, interacting with water. This structure traps oily dirt in the center, allowing it to be washed away.

Explanation:
Natural gas is a fossil fuel composed primarily of methane (CH4), typically making up 70-90% of its volume. It also contains smaller amounts of ethane, propane, butane, and other heavier hydrocarbons, along with non-hydrocarbon gases like carbon dioxide and nitrogen.