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(a) Definition of diffusion; The process by which molecules of different substances move randomly among one another. OR Intimate mixing of molecules/atoms/particles of different substance (as a result of kinetic energy) (b) Factors that affect the rate of diffusion - density of substance - mass of substance - temperature

(a) (i) Newton’s law of Universal Gravitation; Any two bodies in the universe attract each other with a force that is (directly) proportional to the product of their masses and inversely proportional to the square of the distance between them. (ii) Definition of gravitational field; A region/space in which gravitational force is felt / experienced. (b) (i) Derivation of the equation relating G and g at the surface of the earth F = \(\frac{GMm}{R^2}\) mg = \(\frac{GMm}{R^2}\) g = \(\frac{GM}{R^2}\) (ii) Assumptions for which equation holds; - mass of the earth is concentrated at its centre - earth is spherical - earth is not rotating - possesses uniform density. (c) Calculation of the force of attraction between a star and the earth; F = \(\frac{GM_sM_e}{r_2}\) = 6.67 x 10\(^{11}\) [\(\frac {(2 \times 10^{30}) (5.98 \times 10^{24})} {(1.5 \times 10^{11})^2}\)] = 3.55 x 10\(^{22}\)N (d) (i) Definition of escape velocity; The minimum uni-directional speed/velocity required by a body to leave the gravitational field/influence of a planet (ii) Differences between acceleration of free fall (g) and universal gravitational constant (G) g G Its unit is N m2 kg-2 Its unit is m s-2 / N kg-1 It is constant everywhere It varies from place to place It is a scalar quantity It is a vector quantity

(a)(i) Explanation of latent heat When a substance is changing state, it absorbs/gives out thermal/heat energy which does not result in temperature change. This heat absorbed or given out during change of state is known as latent heat. (ii) Factors that affect the rate of evaporation of a liquid - exposed surface area of the liquid - temperature of the liquid - wind / draught - humidity / amount of water vapour - nature of the liquid - air pressure. (b) Explanation of observations (i) Water in a clay pot is cooler than water in a closed plastic container The clay pot has pores which allow evaporation to take place. In the process of evaporation, molecules take latent heat from the bulk of the water, leaving the water cooler; but the plastic container does not have pores (to allow for evaporation). (ii) Food gets cooked faster in a pressure cooker than in an ordinary cooking pot With the pressure cooker, increased pressure raises the boiling point of water within a short period. This leads to faster cooking. Ordinary cooking pot operates at normal atmospheric pressure. (c) Effects of heat on a substance Change of/in: - state - temperature - dimension - colour - electrical resistance (d) (i) Determination of latent heat of fusion of the body Heat supplied by electric heater in the first 1400 s IVt\(_1\) = mlf mlf = 12 x 40 x 1400 = 6.72 x 105J (ii) Determination of Specific heat capacity of the body IVt\(_2\) = mc\(\Delta \theta\) c = \(\frac{IVt_2}{m \Delta \theta}\) = \(\frac{12 \times 40 \times 72}{1.5 \times 60}\) = 384 Jk\(^{-1}\) K\(^{-1}\)

(a) (i) Definition of force Action/push/pull that changes/tends to change the state of rest or of uniform motion in straight line. Its unit is newton (N) (ii) Types of solid friction - dynamic (friction) - static (friction) (b) (i) Velocity-time graph for journey

The expected answer is: (a) (i) Identification of labelled parts of photocell A - Emitter / cathode B - Collector / anode (ii) Function of part of photocell A - emits electrons B - attracts electrons (iii) Meaning of terms in Einstein’s photoelectric equation E - kinetic energy of photoelectrons hf - energy of incident photon Wo - work function of metal

No expanded working has been attached for this question yet. The verified answer is Option B.

No expanded working has been attached for this question yet. The verified answer is Option B.

No expanded working has been attached for this question yet. The verified answer is Option C.

K.E = mgh but h = 80m, m = 2kg, g = 10m/s^2 K.E = 2 x 10 x 80 = 1600J.

No expanded working has been attached for this question yet. The verified answer is Option C.

No expanded working has been attached for this question yet. The verified answer is Option C.

Elastic Force: This is the force exerted by the spring when it is compressed or stretched. It is the elastic force that directly acts to restore the spring to its equilibrium position.

No expanded working has been attached for this question yet. The verified answer is Option C.

The vacuum of a thermos flask prevents heat loss by conduction and convection, conduction because vacuum is a poor conductor of heat, convention because the space between the walls is a vacuum which reduces the heat loss due to conduction and convection. if there is any atmospheric air or material between then there will be some amount of heat transfer through the conduction and convection

Heat needed to change 60g (0.06kg) of ice at 0\(^o\)C to water at 0\(^o\) = 0.06 x 3.36 x 10\(^5\)J = 0.2016 x 10\(^5\) J Heat required to raise the temp. of 60g (0.06kg) of water from 0\(^o\)C to 80\(^o\)C = 0.06 x 4.2 x 10\(^3\) x (80.0)J = 0.06 x 4.2 x 10\(^3\) x 80 = 20.16 x 10\(^3\) = 0.2016 x 10\(^5\) Total heat needed = (0.2016 + 0.2016) 10\(^5\)J = 0.4032 x 10\(^5\) J = 40.32KJ