Difference Between Fluid and Liquid

Introduction

Liquids and gases are two forms of matter which tend to flow. Fluid substances also tend to flow. The ability to flow through its properties exists in only two states of matter - Liquid and gases. All three forms of matter act differently due to the differences in their intermolecular forces of attraction between particles. The arrangement of particles in substances gives compactness, rigidity, or fluidity. The substances tend to flow easily because of the larger inter-molecular spaces between particles. Liquids exhibit flow due to their molecular arrangement and spaces present between particles. Also, gases have large intermolecular spaces between them and tend to flow.

What is Fluid?

• Fluids are either liquids or gases.

• They tend to flow.

• A fluid flows under the action of force or pressure.

• Examples are toothpaste, oxygen, hydrogen, water, petrol, sulphuric acid, molten lava, etc.

Physical Properties of Fluid

The physical properties of fluids include −

Density

It is the ratio of the mass of the fluid to its volume.

$$\mathrm{d=\frac{m}{v}}$$

Where, d=density

$$\mathrm{m=mass}$$

$$\mathrm{v=volume}$$

According to the above expression, density is directly proportional to mass and inversely proportional to its volume. It means the more the mass, the more will be its density. For example- A gel is denser than an emulsion (mixture of liquids) as the gel is semi-solid, while emulsions are liquids. Therefore, the flow will be more in less dense substances.

Specific weight

It represents the force exerted by gravity on a unit volume of a fluid.

Viscosity

It is the resistance to the flow of fluids. It depends on the thickness of the substances. It also depends on the temperature.

Graphical representation of viscosity versus temperature − Viscosity of gases rapidly increases with an increase in temperature, and the viscosity of liquids decreases with an increase in temperature. The reason is the substances tend to flow more easily as an increase in the intermolecular spaces between them. Therefore, heating liquids flow more easily, whereas gases flow more slowly.

Surface tension

The property of the surface of a liquid allows it to resist an external force due to the cohesive nature of the water molecules. Liquids tend to acquire the least surface area possible.

Differences between Liquids and Gases

On the basis	Liquids	Gases
Volume and Density	It has fixed volume and moderate density, as an intermolecular force of attraction between molecules is strong.	There is no definite volume or low density, as the intermolercular attraction among particles is weak.
Diffusion	Diffusion is higher than solids.	Highly diffusable as particles move randomly at high speed.
Rigidity or fluidity	Less rigidity and can flow easily.	No rigidity and can flow easily.
Shape	It has no definite shape and takes the shape of a vessel.	They do not have a definite shape.
The kinetic energy of particles at a given temperature	Higher than solids, as liquids have more intermolecular space than solids.	Maximum kinetic energy, as it has larger intermolecular spaces.

What is Liquid?

A liquid is a substance that flows freely and has a definite volume. For example oil and water.

Physical Properties of Liquid

The two properties give a suitable way of distinguishing the liquid state from the solid and gaseous state.

• Retention of its volume

  Liquids have a fixed volume as long as they are not undergoing any vapourization or change in temperature.

• The conformation or shape of its container

  Liquids have the property to attain that particular shape of their own when put into any vessel.

The Difference between the Fluid and the Liquid

Fluid	Liquid
A sort of matter or a common state of some things is fluid.	One of the three states or phases of matter is liquid
Flowing fluids have certain viscosity (thickness).	Liquids have volume and flow, but they lack defined shape.
Fluids travel with liquids.	Every liquid is fluid.
A substance that lacks stiffness cannot withstand force when applied, making it fluid.	Liquids are comparatively incompressible and can take on the form of any tank or container.

Fun Facts

• Without a container, liquids form a puddle or pool.

• Oil does not mix with water. Though it behaves like a small puddle in water.

• Mercury is metal though it is a liquid at room temperature.

• Liquid flow to fill the space around them.

• Fluids like shampoo and moisture are made of essential oils and give off a distinctive scent, though they are not essentials.

• Liquids can transfer heat from hotter to colder bodies.

• Fluids that flow slowly have a high viscosity.

• Most substances will turn to liquid if they are heated up. Even rocks turn into semi-liquids called lava.

• A fluid whose density does not change with a change in pressure is incompressible.

• Liquid oxygen is magnetic, can be moved around, and even picked up with a powerful magnet.

Conclusion

The fluidity of a substance is the measure of the tendency to flow. Both liquids and gases possess the characteristics of flowing. The fluids are both gases and liquids. On the other hand, the liquid is only one state of matter. Though, both possess common characteristics of flow. In various factors, fluids are different from liquids- viscosity, surface tension, and density. However, the liquid (water) has a fixed volume and takes the shape of the container in which it is present.

FAQs

1. Is water a liquid or fluid?

Water is a liquid and has cohesion. It also acts as fluid at ambient pressure and temperature. It has an open structure full of voids, especially at low temperatures.

2. What kind of fluid is air?

Air is a mixture of gases. However, it exists with moisture, smoke particles, and gases. But under normal conditions, the air is a gas.

3. Is electricity fluid?

Electricity is the flow of charges, just like water. Yes, charges in electricity are the flow of electrons like a continuous fluid.

4. What exertion of pressure is maximum and least when it is full of water?

When a container is full of water, the pressure is equal in every part of the container. But there is a slight difference between the bottom and top of the container. Pressure at the bottom is maximum and least at its top.

5. Does fluid density change?

The amount of the liquid is almost unchanged, and fluid density is always constant. Between gases and liquids, only liquids are incompressible fluids, as density changes caused by temperature and pressure are the least.

6. What is the effect of heat on liquids?

When heat is applied, the liquid expands moderately. The reason is that particles of liquid move around each other faster where the force of attraction between these particles is less than solids making liquids expand more than solids.