Physics- P6: Molecules and Matter

Density

A substance’s mass per unit volume

How is density calculated?

Mass (kg) /volume (m³)

Method for measuring density of a regular solid

\-Measure mass of object using electronic balance

\-Measure volume of solid using a ruler (LxWxH)

\-Density=mass/volume

Method for measuring density of a irregular solid

\-Measure mass of object using electronic balance

\-Lower object on a thread into measuring cylinder partly filled with water

\-Calculate volume by rise in water level

\-Density= mass/volume

Method for measuring density of a liquid

\-Use measuring cylinder to find volume of liquid

\-Measure mass of empty beaker using a balance

\-Pour liquid from measuring cylinder into beake

\-Use balance to measure total mass of beaker/liquid again

\-Calculate the mass of liquid by subtracting

\-Input into formula density= mass/volume

How can a density be used to determine whether it will float in water?

If the density is less than 1000kg/m3 (density of water) then it will float

Why do the mass of a substance stays the same when the state changes?

The number of particles stay the same despite its more/less condensed

What is the differences between boiling and evaporation?

\-Boiling occurs throughout a liquid at its boiling point

\-Evaporation occurs from the surface of a liquid when its temperature is below its boiling point

What is the internal energy of a system?

\-The energy of the particles that is caused by their individual motion and positions

\-Kinetic energy+Potential energy

How does heating a substance affect its internal energy if its temp rises without changing state?

Particle energy increases

How is internal energy changed in a substance if it changes state without a temperature change.

Latent heat

Energy needed for the substance to change state without a temperature change

Specific latent heat of fusion

The energy needed to melt 1 kg of substance without changing its temperature

Specific latent heat of fusion formula

Energy (J)/Mass (KG)

Specific latent heat of vaporisation formula

Energy (J)/Mass (KG)

Specific latent heat of evaporation

\-The energy needed to boil 1 kg of substance without changing its temperature

What is the difference between specific heat capacity and specific latent heat?

\-Specific heat capacity is the energy needed to change temperature

\-Specific latent heat is energy needed to change state

How does gas exert pressure on a surface?

Gas molecules on a surface collide with other gas molecules, building pressure

How does the pressure of a gas in a sealed container affected by temperature change?

Temp increases, pressure increases because molecules move faster and have more energy, meaning more collisions