Density is the mass per unit volume of a material.

Why is a gas generally less dense than the same substance in solid form?

In a gas, the particles are more spread out, so the same mass occupies a much larger volume, giving a lower density .

Density is defined as the ______ per unit ______ of a material.

Density is defined as the mass per unit volume of a material.

True or False? A balloon is less dense than a small bar of lead, despite occupying a larger volume.

True. Density depends on mass per unit volume, not size — the balloon has a far smaller mass for its volume than the lead.

Describe how the volume of an irregularly shaped object is measured using a displacement ("Eureka") can.

The eureka can is filled with water up to the spout, with a measuring cylinder placed below it. The object is lowered carefully into the can, and the volume of water displaced into the measuring cylinder equals the volume of the object .

How is the mass of a liquid calculated in the core practical to determine the density of a liquid?

Mass of liquid = mass of cylinder with liquid − mass of empty cylinder

A ______ is used to measure the mass of an object in the density practical.

A digital balance is used to measure the mass of an object in the density practical.

True or False? Taking repeat readings and averaging reduces systematic error in the density practical.

False. Repeat readings and averaging reduce random error . Systematic errors, such as a balance not reading zero, must be removed by correct technique instead.

Give one way of reducing systematic error in the density practical.

Ensure the digital balance reads zero before taking any mass measurements.

Why must an irregular object be lowered carefully into the eureka can, rather than dropped in?

Dropping the object may cause water to splash out , leading to an inaccurate (too low) reading of the displaced volume.

Pressure is the concentration of a force, or the force per unit area .

Why do tractors have large tyres?

Large tyres spread the tractor's weight (force) over a larger area , reducing the pressure and preventing the tractor from sinking into soft ground such as mud.

Why can a nail be hammered into a wall more easily than a blunt object of the same weight?

The nail's sharp point has a very small area , which concentrates the force to produce a large pressure, allowing it to be pushed into the wall.

If a given force is spread over a smaller area, the pressure produced is ______ .

If a given force is spread over a smaller area, the pressure produced is larger .

True or False? A person wearing high heels exerts a lower pressure on the ground than the same person wearing flat shoes.

False. High heels concentrate the same weight over a much smaller area than flat shoes, producing a higher pressure.

A fluid is a substance that is either a liquid or a gas .

In which direction do the forces created by fluid pressure act on a surface?

At 90 degrees (at right angles, or normal) to the surface.

How does the pressure exerted on an object in a fluid change with depth?

Pressure increases with depth — the deeper the object, the greater the pressure exerted on it.

The pressure of a fluid is exerted ______ across the whole surface of an immersed object, and in all ______ .

The pressure of a fluid is exerted evenly across the whole surface of an immersed object, and in all directions .

True or False? The pressure exerted by a fluid on an immersed object depends on the shape of the object.

False. Pressure depends on the depth , the fluid's density and the gravitational field strength — not on the shape of the object.

IGCSEPhysicsEdexcelPhysics (Modular)Unit 1Flashcards4. Solids, Liquids & Gases: Part 1Density & Pressure

Density & Pressure (Edexcel IGCSE Physics (Modular): Unit 1): Flashcards

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Cards in this collection (27)

Define density.
Density is the mass per unit volume of a material.
What is the equation linking density, mass and volume?
$ρ = \frac{m}{V}$
Where ρ = density (kg/m³), m = mass (kg), V = volume (m³)
Why is a gas generally less dense than the same substance in solid form?
In a gas, the particles are more spread out, so the same mass occupies a much larger volume, giving a lower density.
A paving slab has a mass of 73 kg and a volume of 0.017 m³. Calculate its density, to two significant figures.
$ρ = \frac{m}{V} = \frac{73}{0.017} = 4300 {kg/m}^{3} (2 s.f.)$
Density is defined as the ______ per unit ______ of a material.
Density is defined as the mass per unit volume of a material.
True or False?
A balloon is less dense than a small bar of lead, despite occupying a larger volume.
True.
Density depends on mass per unit volume, not size — the balloon has a far smaller mass for its volume than the lead.
Describe how the volume of an irregularly shaped object is measured using a displacement ("Eureka") can.
The eureka can is filled with water up to the spout, with a measuring cylinder placed below it. The object is lowered carefully into the can, and the volume of water displaced into the measuring cylinder equals the volume of the object.
How is the mass of a liquid calculated in the core practical to determine the density of a liquid?
Mass of liquid = mass of cylinder with liquid − mass of empty cylinder
A ______ is used to measure the mass of an object in the density practical.
A digital balance is used to measure the mass of an object in the density practical.
Which instrument in this practical has a resolution of 0.01 mm?
Vernier callipers
True or False?
Taking repeat readings and averaging reduces systematic error in the density practical.
False.
Repeat readings and averaging reduce random error. Systematic errors, such as a balance not reading zero, must be removed by correct technique instead.
Give one way of reducing systematic error in the density practical.
Ensure the digital balance reads zero before taking any mass measurements.
Why must an irregular object be lowered carefully into the eureka can, rather than dropped in?
Dropping the object may cause water to splash out, leading to an inaccurate (too low) reading of the displaced volume.
Define pressure.
Pressure is the concentration of a force, or the force per unit area.
What is the equation linking pressure, force and area?
$P = \frac{F}{A}$
Where P = pressure (Pa), F = force (N), A = cross-sectional area (m²)
Why do tractors have large tyres?
Large tyres spread the tractor's weight (force) over a larger area, reducing the pressure and preventing the tractor from sinking into soft ground such as mud.
Why can a nail be hammered into a wall more easily than a blunt object of the same weight?
The nail's sharp point has a very small area, which concentrates the force to produce a large pressure, allowing it to be pushed into the wall.
If a given force is spread over a smaller area, the pressure produced is ______.
If a given force is spread over a smaller area, the pressure produced is larger.
True or False?
A person wearing high heels exerts a lower pressure on the ground than the same person wearing flat shoes.
False.
High heels concentrate the same weight over a much smaller area than flat shoes, producing a higher pressure.
A hydraulic piston has a cross-sectional area of 2.73 × 10⁻² m² and the liquid pressure acting on it is 5.28 × 10⁵ Pa. Calculate the force on the piston, giving your answer in kN to 3 significant figures.
$F = P \times A = (5.28 \times 10^{5}) \times (2.73 \times 10^{- 2}) = 14400 N = 14.4 kN (3 s.f.)$
Define a fluid.
A fluid is a substance that is either a liquid or a gas.
In which direction do the forces created by fluid pressure act on a surface?
At 90 degrees (at right angles, or normal) to the surface.
How does the pressure exerted on an object in a fluid change with depth?
Pressure increases with depth — the deeper the object, the greater the pressure exerted on it.
What is the equation for the pressure at a depth in a fluid?
$P = h ρ g$
Where P = pressure (Pa), h = depth of fluid above the object (m), ρ = density of the fluid (kg/m³), g = gravitational field strength (N/kg)
The pressure of a fluid is exerted ______ across the whole surface of an immersed object, and in all ______.
The pressure of a fluid is exerted evenly across the whole surface of an immersed object, and in all directions.
True or False?
The pressure exerted by a fluid on an immersed object depends on the shape of the object.
False.
Pressure depends on the depth, the fluid's density and the gravitational field strength — not on the shape of the object.
A pressure of 20 kPa is exerted at a depth in water of density 1000 kg/m³. Using g = 10 N/kg, calculate the depth of the water.
$h = \frac{P}{ρ g} = \frac{20 000}{1000 \times 10} = 2.0 m$

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