Pressure
The figure shows a device connected to a gas cylinder. The device is used to measure the pressure of the gas inside the cylinder. State the name of the device shown in the figure.
manometer
Define work done.
work done = force × distance moved in the direction of the force
A power station burns fossil fuel to produce electrical energy. State the form of the energy stored in the fuel.
chemical energy
Two containers made of insulating material contain the same volume of water at room temperature. The containers do not have lids. The volume of liquid in each container gradually decreases. After a certain time, the temperature of the water has decreased to below room temperature. Explain, in terms of molecules, why the temperature has decreased. [2]
Energetic water molecules escape from the surface and the less energetic molecules remain so the temperature is lower.
The figure shows a tractor and a car of the same weight. The vehicles drive over the same soft ground. Explain why the car sinks into the soft ground but the tractor does not sink. [2]
tractor has larger area (of tyre(s) in contact with ground)
so (tractor) pressure is less (on the ground)
State the principle of conservation of energy.
Energy cannot be created or destroyed
OR energy can only be transferred from one form to another
OR total energy remains the same
Apart from cost and efficiency, give two other reasons for not building a coal-fired power station. [2]
non-renewable fuel
releases CO2/greenhouse gases OR (contributes to) global warming
Two containers made of insulating material contain the same volume of water at room temperature. The containers do not have lids. The volume of liquid in each container gradually decreases. One of the containers is wide and shallow. The other container is narrow and deep. Predict which container has the greater rate of cooling. Explain your answer. [2]
Water in wide container AND has water with larger surface (area)
Rate of evaporation higher/ faster/ quicker
A diver dives to a depth below the surface of the sea where the total pressure is 3.0 × 105 Pa. The atmospheric pressure is 1.0 × 105Pa. The density of the sea water is 1030 kg/m3. Calculate the depth of the diver below the surface of the sea.
1900 Pa
A load of 12 kg is raised to a height of 1.7 m above the ground. The load is connected to a pulley system. The time taken for the load to fall to the ground is 1200 seconds. The load falls at constant speed. Calculate the rate of transfer of gravitational potential energy as the load falls to the ground.
0.17 W
For each energy resource, state the form of energy stored in:
fossil fuels
water behind hydroelectric dams.
fossil: chemical
water: gravitational potential
Explain, in terms of molecules, why it is possible to compress a gas, but not a liquid. (2)
Gas molecules are far apart while the liquid molecules are close together.
An oil tanker is in a river. The bottom of the tanker is 15 m below the surface of the water. The tanker sails out onto a calm sea. The density of sea-water is greater than the density of river water. State and explain any change in the depth of the bottom of the tanker below the surface. [3]
Depth (below surface) becomes less
because pressure on bottom of tanker is greater
so force on bottom of tanker is higher so tanker rises
A student investigates energy changes when a ball rolls down a curved track. The student holds the ball at a starting point on the curved track, as shown in the figure. The ball is released. It rolls down the track, up the other side to the stopping point and then back down again. Describe the energy changes that take place as the ball rolls from the starting point to the stopping point. [4]
(gravitational) potential energy (of ball)
(is) transformed/transferred to OR becomes kinetic energy (of ball)
kinetic energy transferred to (gravitational) potential energy
as ball rises or moves up slope energy (change) (transferred to) thermal energy (due to friction)
A country needs to build new power stations to provide electricity for homes and industry. One type of power station is a coal-fired power station. Describe how the energy stored in the coal is used in a coal-fired power station to generate electrical energy.
(coal/it is) burnt/burned
(thermal energy from coal used to) heat/boil water
steam (produced) that turns/spins/moves turbine
(which) turns/spins/moves a generator
A quantity of gas is contained in a sealed container of fixed volume. The temperature of the gas is increased. State, in terms of molecules, two reasons why the pressure of the gas increases. [2]
Molecules move faster
Molecules hit walls more often
The figure shows a device that uses liquid pressure to lift heavy boxes. The boxes are lifted by pumping oil into the cylinder. The force upwards on the piston due to the oil, and the force downwards on the piston due to the air above the piston, combine to produce a constant force of 8800 N. The pressure of the air is 1.0 × 105 Pa and the cross-sectional area of the bottom surface of the piston is 0.016 m2. Calculate the pressure of the oil at the bottom surface of the piston.
6.5 x105 Pa
Table 4.1 lists situations in which energy is stored. Complete Table 4.1 by naming the form of energy stored in each situation.
mobile phone: chemical
piece of coal: chemical
rotating wheel: kinetic
water: gravitational potential
Solar panels produce electrical energy. State two advantages and two disadvantages of using solar panels, rather than fossil fuels, to produce electrical energy.
Advantages:
free fuel
renewable
no air pollution / no SO2 / no acid rain
no greenhouse gases
Disadvantages:
needs a lot of space
no energy at night
less energy when cloudy / winter
Explain, in terms of molecules, why a liquid expands more than a solid when heated. [2]
forces between liquid molecules weaker than in solids
less energy / work done to separate molecules or greater separation for same work done