Among the following metals, choose the one which is least like the others in the group.

Introduction / Context:
This is a science based classification question that tests basic knowledge about metals and their physical states. You are asked to pick the metal which is least like the others in the group, given common metals such as zinc, aluminium, mercury, copper and iron.

Given Data / Assumptions:

• The metals in the options are Zinc, Aluminium, Mercury, Copper and Iron.
• All are well known elements and conduct heat and electricity.
• Under normal conditions, most metals are solid at room temperature.
• We assume standard room temperature conditions as used in basic science (around 25 degrees Celsius).

Concept / Approach:
The usual way to approach this kind of question is to check for one metal that has a unique physical property compared with the others. A well known fact from basic chemistry is that almost all metals are solids at room temperature, with one famous exception. If four metals are solid and one is liquid at room temperature, the liquid metal will be the odd one out.

Step-by-Step Solution:
Step 1: Zinc is a bluish white metal that is solid at room temperature.Step 2: Aluminium is a light, silvery metal that is also solid at room temperature. It is widely used in utensils and engineering structures.Step 3: Copper is a reddish brown metal, solid at room temperature, often used in electrical wiring.Step 4: Iron is a hard, strong metal and is also solid at room temperature. It is used in construction, machinery and tools.Step 5: Mercury, however, is very different. It is a silvery metal that is liquid at room temperature. It has historically been used in thermometers and some electrical switches because of this liquid property.Step 6: Thus, zinc, aluminium, copper and iron are all solid metals at room temperature, whereas mercury is a liquid metal under the same conditions.Step 7: Therefore, mercury is the metal which is least like the others in the group.

Verification / Alternative check:
If you imagine holding a piece of each metal at room temperature, zinc, aluminium, copper and iron would all be solid pieces that you can pick up. Mercury cannot be picked up in the same way; it forms a shiny liquid that flows and takes the shape of its container. This simple mental picture confirms that mercury behaves differently from the others at everyday temperatures.

Why Other Options Are Wrong:
Zinc, aluminium, copper and iron share the common property of being solid metals at room temperature, even though they differ in colour, density and usage. Because they share similar state of matter under normal conditions, they form a natural group. They cannot be the odd one out since none of them stands apart in such a striking way as mercury does.

Common Pitfalls:
Some learners may be tempted to pick aluminium because it is lighter than the others, or copper because of its reddish colour. However, the question asks which metal is least like the others in a fundamental sense. The state of matter (solid versus liquid) at room temperature is a much stronger distinguishing feature than colour or density. Remembering that mercury is the only common metal that is liquid at room temperature will help in many similar questions.

Final Answer:
The metal which is least like the others is Mercury.