Free QCE Year 11 Physics Flashcard Review
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Convert θ °C to kelvin.
T(K) = θ(°C) + 273. A temperature change of 1 °C equals 1 K.
Difference between temperature and internal energy?
Temperature is average particle kinetic energy; internal energy is the total kinetic plus potential energy of all particles, so it depends on mass too.
What is heat?
Energy transferred because of a temperature difference, always from hotter to cooler.
How does conduction transfer energy?
Particle collisions pass kinetic energy to neighbours; in metals free electrons carry energy quickly.
How does convection transfer energy?
Heated fluid expands, becomes less dense and rises; cooler denser fluid sinks, forming a current that carries energy.
Why can radiation cross a vacuum?
It is electromagnetic waves (mainly infrared), which need no medium.
Equation for temperature change with no change of state
Q = mcΔT (Q in J, m in kg, c in J kg⁻¹ K⁻¹, ΔT in K).
Why is temperature constant while ice melts?
Added energy increases particle potential energy by overcoming intermolecular attractions, not by breaking covalent O–H bonds or raising average kinetic energy. Internal energy rises while temperature stays constant during melting at fixed pressure.
Equation for energy in a change of state
Q = mL, where L is the specific latent heat of fusion or vaporisation (J kg⁻¹).
State the first law of thermodynamics with signs.
ΔU = Q + W; Q positive into the system, W positive when work is done on the system.
Efficiency formula
η = useful output ÷ total input × 100% (energy or power).
Percentage uncertainty vs percentage error
Uncertainty = absolute uncertainty ÷ value × 100% (precision of a measurement); error = |experimental − accepted| ÷ accepted × 100% (accuracy).
What do A and Z represent in ᴬ_Z X?
A = mass number (protons + neutrons); Z = atomic number (protons).
How many neutrons are in ⁵⁶₂₆Fe?
N = 56 − 26 = 30.
Name two properties of the strong nuclear force.
Acts between all nucleons; very short range (about 3 × 10⁻¹⁵ m); attractive at normal separations, repulsive when extremely close.
Why do heavy stable nuclei have more neutrons than protons?
Neutrons add strong-force attraction without adding electrostatic repulsion, offsetting the long-range repulsion among many protons.
What is an alpha particle and how is it stopped?
A helium nucleus ⁴₂He (charge +2e); stopped by paper or a few cm of air.
What happens inside the nucleus in β⁻ decay?
A neutron changes into a proton, emitting an electron and an antineutrino; Z increases by 1, A unchanged.
Which nuclei undergo β⁺ decay?
Proton-rich nuclei; a proton becomes a neutron, emitting a positron and a neutrino; Z decreases by 1.
What two quantities are conserved in a nuclear equation?
Mass number (nucleon number) and charge (atomic number).