Matter is everything around us that we can touch, hold or weigh — it has mass and takes up space. These notes move from what matter is, through its three common states and how it changes between them, into the deeper physics of solids (elasticity, stress and strain) and fluids (density, pressure, buoyancy, surface tension, capillarity and viscosity).
Matter is the physical "stuff" of the universe, and a clear definition is the starting point for everything that follows.
Matter is defined as anything which:
Besides solid, liquid and gas, which are the other recognised states of matter?
Matter has mass and occupies .
Beyond the common three states, another recognised state is the Bose–Einstein .
When matter is heated or cooled it can pass from one state to another; each direction of change has its own name, and getting the direction right is a frequent exam point.
| Change of state | Direction | Definition |
|---|---|---|
| Melting (Fusion) | Solid → Liquid | A solid turns into a liquid on heating. |
| Freezing (Solidification) | Liquid → Solid | A liquid turns into a solid on cooling. |
| Vaporisation (Boiling) | Liquid → Gas | A liquid turns into a gas, fastest at the boiling point. |
| Condensation | Gas → Liquid | A gas turns into a liquid on cooling. |
| Sublimation | Solid → Gas | A solid changes directly into a gas without becoming liquid. |
| Deposition | Gas → Solid | A gas changes directly into a solid without becoming liquid. |
The change of a solid directly into a gas without becoming liquid is called:
Evaporation is a surface phenomenon that happens:
The change of a gas into a solid directly, without becoming liquid, is called .
For pure water, melting and freezing happen at °C at normal atmospheric pressure.
The solid state is the most ordered state of matter, with particles locked tightly in place.
A solid has:
In a solid, the molecules are:
A solid has a definite shape and a definite .
In a solid the molecules are very closely together.
Solids respond to a deforming force in two opposite ways, which give us the ideas of elasticity and plasticity.
The property by which a body regains its original shape after the deforming force is removed is called:
Which of these is an almost perfectly elastic body?
The property by which a body does NOT regain its original shape after the deforming force is removed is called .
Quartz and phosphor are almost perfectly elastic bodies.
The three common states differ in shape, volume, compressibility, spacing of particles, attraction and motion. The table below compares them point by point.
| S.No. | Solid state | Liquid state | Gaseous state |
|---|---|---|---|
| 1 | Definite shape and volume. | No definite shape; takes the shape of the vessel; definite volume. | Neither a definite shape nor a definite volume. |
| 2 | Incompressible. | Compressible to a small extent. | Highly compressible. |
| 3 | Very little space between particles. | Greater space between particles. | Greatest space between particles. |
| 4 | Particles attract each other very strongly. | Force of attraction less than in solids. | Force of attraction is least. |
| 5 | Particles cannot move freely. | Particles move freely. | Particles in continuous, random motion. |
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Rigidity | rigid | not rigid | not rigid |
| Shape | fixed shape | no fixed shape | no fixed shape |
| Volume | fixed volume | fixed volume | no fixed volume |
| Compressibility | cannot be squashed | cannot be squashed | can be squashed |
Which state of matter is highly compressible?
A liquid has:
In the gaseous state, the force of attraction between particles is .
A liquid has no definite shape and takes the shape of the .
Strain measures how much a body's configuration changes when a force acts on it.
Strain is the fractional change in:
The unit of strain is:
Strain is the fractional change in — in length, volume or shape.
Strain has no because it is a pure ratio.
Stress describes the internal restoring force that a deformed body sets up to resist the change.
Stress is defined as the internal restoring force per unit:
The minimum stress required to break a wire is called:
Stress is of two types: Normal stress and stress.
The maximum deforming force up to which a body keeps its elastic property is the limit of .
The elastic limit marks the boundary of a material's springy behaviour.
The elastic limit is the limit of stress and strain up to which a wire:
Beyond which limit does a material start to deform permanently?
Elastic limit is the limit of stress and strain up to which a wire stays .
The elastic limit marks the boundary of a material's behaviour.
Beyond the elastic limit a material starts to deform permanently.
When a wire is stretched beyond the elastic limit, the strain:
If a wire is stretched beyond the elastic limit and the force removed, the wire:
If a wire is stretched beyond the elastic limit, the increases much more rapidly.
After stretching beyond the elastic limit, if the force is removed the wire does not return to its natural .
Push the deformation far enough and the material finally gives way.
The point at which a wire finally breaks is called the:
The fracture point comes after which type of behaviour?
If deformation is increased further beyond plastic behaviour, the wire breaks at a point called the point.
The fracture point is reached when deformation is increased beyond behaviour.
How a material behaves between the elastic limit and the fracture point decides whether it is ductile or brittle.
A ductile material shows:
A brittle material:
In a material, large deformation occurs between the elastic limit and the fracture point.
In a brittle material, the wire breaks soon after the elastic is crossed.
A quick recap of the headline facts about solids most likely to be asked.
Which statement about solids is correct?
The particles of a solid are:
Solids cannot be easily .
The particles of a solid are in fixed positions with little between them.
Repeated stress slowly wears down a material's elasticity.
The property by which an elastic body becomes less elastic under repeated deforming force is called:
Because of elastic fatigue, bridges:
The property by which an elastic body becomes less elastic under repeated alternating deforming force is called elastic .
Because of elastic fatigue, become less elastic after long use and are eventually declared unsafe.
Liquids and gases share a key feature — they can flow — and are grouped together as fluids.
A fluid is a substance that:
Which of these are fluids?
A fluid is a substance that begins to under an external force.
Both liquids and are fluids.
Density tells us how much mass is packed into a given volume of a substance.
Density is the ratio of:
The density of water is maximum at:
Density is a scalar quantity; its SI unit is .
The density of water is maximum at °C.
A hydrometer is the floating instrument used to check how dense a liquid is.
A hydrometer is used to measure the:
The working of a hydrometer is based on:
A hydrometer measures the density (relative density) of a .
A hydrometer works on Principle — a floating body displaces a weight of liquid equal to its own weight.
A fluid at rest presses on every surface it touches, and that thrust per unit area is fluid pressure.
The SI unit of fluid pressure is:
Fluid pressure is the thrust exerted by a liquid per unit:
Fluid pressure is the thrust exerted by a liquid per unit of the surface in contact, at rest.
The unit of fluid pressure is N/m² or .
The weight of the air above us presses down as atmospheric pressure, and it changes with altitude.
As altitude increases, atmospheric pressure:
At sea level, the atmospheric pressure is:
Higher altitudes have pressure because there is less air above you.
At sea level, pressure equals 1 .
A barometer measures air pressure; the liquid-free aneroid type is handy for finding altitude too.
An aneroid barometer measures atmospheric pressure and the:
Which of these is a unit of atmospheric pressure?
An aneroid barometer measures atmospheric pressure and the of a place.
Other units of atmospheric pressure are torr and .
Pascal's Law explains why a small push on a confined liquid can be felt everywhere in it equally.
Pascal's Law states that pressure applied to a confined fluid is transmitted:
Which device works on Pascal's Law?
Pressure applied at any point of a confined fluid is transmitted equally and undiminished in all .
Hydraulic lift, hydraulic press and hydraulic work on Pascal's Law.
Anything dipped in a fluid feels an upward push — the buoyant force.
The upward force acting on a body immersed in a liquid is due to:
The buoyant force equals the weight of the:
The buoyant force equals the weight of the liquid by the submerged part of the body.
The buoyant force acts at the centre of .
Archimedes' Principle is the rule that ties a body's apparent loss of weight to the liquid it pushes aside.
According to Archimedes' Principle, the loss in weight of an immersed body equals the:
If a body weighs 10 N in air and 6 N in a fluid, its loss in weight is:
According to Archimedes' Principle, loss in weight equals the weight of liquid .
When a body is partly or fully immersed in a fluid, its weight falls.
The surface of a liquid behaves like a stretched elastic skin that tries to shrink to the smallest area.
Surface tension is the property by which a liquid tries to:
Because the minimum surface area for a given amount of liquid is a sphere, rain drops are:
The minimum surface area for a given amount of liquid is the , so rain drops are spherical.
Surface tension makes liquid drops behave like tiny .
Surface tension is not fixed — temperature and dissolved impurities change it.
As temperature increases, surface tension:
At the critical temperature, surface tension becomes:
Highly soluble impurities the surface tension of a liquid.
At the critical temperature, surface tension becomes .
Everyday observations — soap cleaning grease, soup spreading on the tongue — all flow from surface tension.
Adding soap or detergent to water:
Adding salt to water:
Kerosene sprinkled on water decreases surface tension, so mosquito floating on it sink and die.
Warm soup is tasty because at high temperature its surface tension is , so it spreads over the tongue.
A liquid can climb (or fall) inside a very thin tube all by itself — this is capillarity.
Capillarity is the rise or fall of a liquid column in a:
A capillary tube is a glass tube of:
Capillarity is the rise or fall of a liquid column in a tube.
A capillary tube is a glass tube of very fine .
Many familiar effects, from blotting paper to plant roots, are capillarity in action.
Blotting paper soaks ink because its pores act as:
Root hairs of plants draw water from the soil through:
Oil rises in a lamp by capillary action of the threads.
Farmers loosen and break up the soil to prevent water loss by action.
The pull between molecules takes two forms depending on whether the molecules are alike or different.
The force of attraction between molecules of the same substance is called:
The attraction of water to glass is an example of:
The force of attraction between molecules of different substances is called force.
Cohesion is the same substance attracted to itself, e.g. water to water by bonding.
When liquid layers slide past one another, an internal friction opposes the motion.
Viscous force opposes the relative motion between different layers of a:
Viscous force is best described as a form of:
Viscous force is the force that opposes the relative between different layers of a liquid or gas.
When liquid layers slide past one another, an internal opposes the motion.
Viscosity measures how "thick" or resistant to flow a fluid is.
Viscosity is a property of:
The viscosity of a liquid is due to the:
The viscosity of a gas is due to of molecules from one layer to another.
Viscosity is the property by which a liquid opposes relative motion between its different .
Take 5 questions at a time — tap an option to check. After each round, revise the notes above and take the retest for 5 fresh questions, until you've mastered the whole chapter.