Density & Pressure (Edexcel IGCSE Physics)

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  • Define density.

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  • Define density.

    Density is defined as the mass per unit volume of a material. It describes how much mass is contained in a given volume.

  • True or False?

    Objects made from high-density materials typically have low mass.

    False.

    Objects made from high-density materials typically have a high mass.

  • What is the equation for the density of an object?

    The equation for density is rho space equals space m over V

    Where:

    • ρ = density, measured in kg / m3

    • m = mass, measured in kilograms (kg)

    • V = volume, measured in metres cubed (m3)

  • State the units for density when mass is in grams (g) and volume is in cubic centimetres (cm³).

    The units for density are grams per cubic centimetre (g/cm³) when mass is measured in grams (g) and volume in cubic centimetres (cm³).

  • Why are gases generally less dense than solids?

    Gases are generally less dense than solids because the molecules in a gas are more spread out over a larger volume.

  • True or False?

    Density is a scalar quantity.

    True.

    Density is a scalar quantity.

  • Define volume.

    Volume is the amount of space occupied by an object in three-dimensional space.

  • State the equation used to calculate the volume of an object.

    The equation used to calculate the volume of an object is V space equals space l space cross times space w space cross times space h

    Where:

    • l = length of object, measured in metres (m)

    • w = width of object, measured in metres (m)

    • h = height of object, measured in (m)

  • Identify which object is more dense, the one on the left or the one on the right.

    Two transparent cubes: the left cube has 4 pink spheres inside, and the right cube has 14 tightly packed pink spheres.

    The object on the right is more dense because the particles are packed more closely together.

  • What is the aim of the core practical on measuring the density of regularly shaped objects?

    The aim of the core practical on measuring the density of regularly shaped objects is to determine the density by measuring the object dimensions

  • Define the term density.

    Density is the mass per unit volume of a substance.

  • What does a digital balance measure?

    A digital balance measures the mass of objects.

  • What is the independent variable in the core practical on measuring the density of regularly shaped objects?

    The independent variable in the core practical on measuring the density of regularly shaped objects is the type of shape/volume.

  • True or False?

    A Vernier caliper measures objects up to 0.01 mm in diameter.

    True.

    A Vernier caliper measures objects up to 0.01 mm in diameter.

  • What is a displacement eureka can used for?

    A displacement eureka can is used to measure water displacement from irregularly shaped objects.

  • How can the density of a liquid be determined?

    The density of a liquid can be determined by measuring its mass and volume, then using the equation for density.

  • What is the resolution of a digital balance?

    The resolution of a digital balance is 0.01 g.

  • What is the method used to determine the density of irregularly shaped objects?

    The displacement technique is used to determine the density of irregularly shaped objects.

  • What is pressure?

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

  • State the equation relating pressure, force and area.

    The equation for pressure, force and area is P space equals space F over A

    Where:

    • P = pressure, measured in pascals (Pa)

    • F = force, measured in newton's (N)

    • A = surface area, measured in metres squared (m2)

  • True or False?

    Pressure is measured in pascals (Pa).

    True.

    Pressure is measured in pascals (Pa).

  • What is the relationship between force, pressure and surface area?

    A force applied over a large area will result in a small pressure, and vice versa.

  • True or False?

    A high-heeled shoe produces the same pressure on the ground as a flat-soled shoe when worn by the same person.

    False.

    A high-heeled shoe produces a higher pressure on the ground than a flat-soled shoe when worn by the same person.

    This is because the same force is applied over a smaller surface area.

  • Why do tractors need large tyres?

    Tractors need large tyres to spread their weight over a large area to reduce the pressure they exert on the ground.

    This prevents them from sinking into the mud.

  • What happens when a force is applied to a nail placed against a wall?

    When a force is applied to the nail, it pierces and enters the wall.

    This is because the applied force is concentrated at the sharp pointed end, which produces a large pressure over a small area.

  • True or False?

    The area used in calculating the pressure should always be the cross-sectional area of the object.

    True.

    The area used in calculating the pressure should always be the cross-sectional area of the object.

    This is the area which is perpendicular (90 degrees) to the applied force.

  • A box is placed on a table. Calculate the pressure applied by the grey face of the box onto the table.

    A rectangular prism with dimensions labeled as 4 meters tall, 3 meters wide, and 2 meters deep. It is noted to weigh 24 newtons.

    The pressure applied by the grey face of the box onto the table is 4 Pa.

    • surface space area space equals space 3 space cross times space 2 space equals space 6 space straight m squared

    • P space equals space F over A space equals space 24 over 6 space equals space 4 space Pa

  • Define a fluid.

    A fluid is either a liquid or a gas.

  • How does a liquid exert force on an object suspended in it?

    When an object is suspended in a liquid, it exerts pressure evenly across the whole surface of the object and in all directions.

    This pressure creates a force which acts at 90 degrees (right angles) to each surface.

  • How does increasing depth and density affect the pressure of a liquid?

    The pressure of a liquid increases with both increased depth and increased density of the liquid.

  • True or False?

    The force created by pressure in a liquid is exerted on an object in one direction only.

    False.

    The force created by pressure in a liquid is exerted evenly across the whole surface of an object.

  • State the equation for the pressure difference of an object in a fluid.

    The equation for the pressure difference of an object in a fluid is increment p space equals space rho g increment h

    Where:

    • increment p = change in pressure, measured in pascals (Pa)

    • rho = density of the liquid, measured in kilograms per metre cubed (kg/m3)

    • g = gravitational field strength on Earth, measured in newtons per kilogram (N/kg)

    • increment h = change in depth of the object in the liquid, measured in metres (m)

  • State the meaning of increment p in equation increment p space equals space rho g increment h.

    In the pressure equation for liquids increment p represents the change in pressure in pascals (Pa).

  • State the meaning ofspace rho in the equation increment p space equals space rho g increment h.

    rho in the pressure equation for liquids stands for the density of the liquid, measured in kilograms per metre cubed (kg/m³).

  • What quantities are needed to calculate the depth of water in a swimming pool?

    The depth of water in a swimming pool can be calculated using the pressure equation: increment p space equals space rho g increment h

    The quantities needed to calculate depth increment h are:

    • increment p = the pressure of the water at the bottom of the pool

    • space rho = the density of the water

    • g = the gravitational field strength of Earth

  • State the property of pressure in a liquid demonstrated in the diagram.

    Diagram showing three water jets from a pressurized tank, labeled with weakest jet at the top (low pressure) and strongest jet at the bottom (high pressure) with a ruler below.

    The property of pressure in a liquid demonstrated in the diagram is that pressure increases with depth.