In everyday liquids at room temperature, consider pure water and common cooking oil: compared to cooking oil, is water generally more dense or less dense?

Introduction / Context:
Density is an important physical property that describes how much mass is contained in a given volume of a substance. Everyday observations in the kitchen, such as oil floating on water, provide simple demonstrations of density differences between liquids. This question asks whether the statement 'Water is more dense than cooking oil' is correct or incorrect under typical room temperature conditions.

Given Data / Assumptions:

• We are comparing pure water with common cooking oils such as vegetable oil, sunflower oil or mustard oil at room temperature.
• Water has a density close to 1.0 g/cm³ (1000 kg/m³) at room temperature.
• Most common cooking oils have densities less than that of water, typically around 0.9 g/cm³ or slightly lower.
• We assume normal atmospheric pressure and no unusual additives in the liquids.

Concept / Approach:
When two immiscible liquids, such as oil and water, are placed in the same container, the liquid with lower density floats on top of the liquid with higher density. In kitchen experiments, oil poured onto water clearly floats, forming a distinct layer above the water. This observation indicates that oil is less dense than water and therefore water must be more dense than oil. Quantitatively, the density of pure water at room temperature is about 1 g/cm³, while common cooking oils typically have densities around 0.9 g/cm³. Since 1.0 is greater than 0.9, water is more dense, making the statement in the question correct.

Step-by-Step Solution:
Step 1: Recall the definition of density as density = mass / volume.Step 2: Note that for two liquids in the same gravitational field, the one with lower density tends to float on the one with higher density if they do not mix.Step 3: Observe that in everyday life, cooking oil floats on water rather than sinking.Step 4: Conclude from this observation that oil must be less dense and water must be more dense.Step 5: Compare typical numerical densities: water ~ 1.0 g/cm³, cooking oil ~ 0.9 g/cm³.Step 6: Confirm that 1.0 g/cm³ > 0.9 g/cm³, so the statement 'Water is more dense than cooking oil' is correct.

Verification / Alternative check:
Scientific tables of physical properties list the density of water at 20°C as about 0.998 g/cm³ and many vegetable oils in the range 0.90–0.93 g/cm³. Classroom demonstrations and science experiments frequently show a beaker with water and a layer of oil floating on top to visually illustrate density differences. These independent sources and observations agree that water is more dense than cooking oil under ordinary conditions.

Why Other Options Are Wrong:
Option B claims that cooking oil is more dense than water, which contradicts both experiments and numerical data. Option C suggests that density depends only on container shape, which is incorrect; density is a property of the material itself and does not change with container shape. Option D says that their densities are always exactly equal, which is false because numerical values clearly differ. Only option A accurately reflects the physical reality.

Common Pitfalls:
Some learners may remember that ice floats on water and wrongly generalise that the lighter-looking liquid or solid is always water. Others may not have carefully observed oil-water experiments and assume they mix or that the order of layers is random. To avoid confusion, always rely on the definitions and simple experiments: the substance that floats has lower density, and in the case of oil and water, oil floats and water sinks beneath it.

Final Answer:
The statement is correct: under normal conditions, water is more dense than common cooking oil.