**Metals vs Non-metals: Physical Properties**

Metals and non-metals are two distinct categories of elements based on their physical and chemical properties. In this response, we will discuss the distinction between metals and non-metals based on various physical properties.

**Existence:**
- Metals: Most metals are solid at room temperature, with a few exceptions like mercury.
- Non-metals: Non-metals can exist in all three states of matter - solid, liquid, and gas. Examples include oxygen (gas), sulfur (solid), and bromine (liquid).

**Luster:**
- Metals: Metals generally have a shiny and reflective surface, known as metallic luster.
- Non-metals: Non-metals lack metallic luster and are generally dull or have a glassy appearance.

**Hardness:**
- Metals: Metals tend to be hard, although there are exceptions like sodium and potassium, which are soft enough to be cut with a knife.
- Non-metals: Non-metals have varying degrees of hardness. Some non-metals like diamond are extremely hard, while others like sulfur are relatively soft.

**Density:**
- Metals: Metals are generally dense materials. For example, iron and lead have high densities.
- Non-metals: Non-metals have lower densities compared to metals. For instance, gases like hydrogen and helium have very low densities.

**Conductivity:**
- Metals: Metals are good conductors of heat and electricity. They possess a high degree of metallic bonding that allows the movement of electrons, leading to their excellent conductivity.
- Non-metals: Non-metals are generally poor conductors of heat and electricity. They lack the free-moving electrons required for efficient conduction.

**Malleability and Ductility:**
- Metals: Metals are malleable, meaning they can be hammered or pressed into different shapes without breaking. They are also ductile, which means they can be drawn into thin wires.
- Non-metals: Non-metals are generally brittle and cannot be easily shaped or stretched without breaking.

In conclusion, metals and non-metals can be distinguished based on several physical properties. Metals exist primarily as solids, have metallic luster, are generally hard and dense, exhibit high conductivity, and possess malleability and ductility. On the other hand, non-metals can exist in all states, lack metallic luster, have varying degrees of hardness and density, are poor conductors of heat and electricity, and are generally brittle. Understanding these distinctions is essential for categorizing and studying the properties of different elements in the periodic table.