Additional Science

Question 1

Describe the structure of the atom, limited to the position, mass and charge of protons, neutrons and electrons

Answer 1

An atom is made up of a positive nucleus containing positively charged protons and neutrons, which have no charge. Orbiting the nucleus are electrons which have the same size charge as a proton, but it is a negative charge, not a positive one. Protons and neutrons have the same mass, but electrons are much smaller

Question 2

Explain how an insulator can be charged by friction, through the transfer of electrons

Answer 2

When two insulators are rubbed together surface electrons are transferred from one material to another. The material that gains electrons will gain a negative charge. The material that loses electrons will be left with a positive charge.

Question 3

Explain why a material gaining electrons becomes negatively charged and a material losing electrons is left with an equal positive charge

Answer 3

Most materials have an equal number of positive and negative charges. If a material gains electrons it will have more negative charges then positive charges ? This leaves it with an overall negative charge. If a material loses electrons then it will have more positive charges than negative, and so it will have an overall positive charge.

Question 4

Describe what happens when two like, or two opposite charges are brought together

Answer 4

Two like charges repel, but two opposite charges will attract.

Question 5

Explain in terms of the movement of electrons why you can get a shock from an a car door

Answer 5

When the car drives across the floor, the rubber tyres rub against the road ? this leads to a transfer of electrons from the road to the car. When you touch the car door the excess electrons travel from the car into you ? resulting in a shock.

Question 6

Explain in terms of the movement of electrons how lightning works

Answer 6

Clouds contain ice. As the cloud moves the ice particles collide together and this results in a negative charge being built up at the bottom of the cloud (and a positive charge at the top). As this charge increases the voltage increases. Eventually there is enough voltage to create a bolt of lightning and the electrons travel in a powerful stream towards the ground.

Question 7

Explain in terms of the movement of electrons how a balloon sticks to a wall

Answer 7

When you rub a balloon it gains a negative charge. When this balloon is brought near a wall the negative charge of the balloon pushes the electrons in the surface of the wall away. This results in the front of the wall having a positive charge. The positive charge of the wall will attract the negatively charged balloon.

Question 8

Explain why a tanker is earthed, and how this can help to prevent an explosion

Answer 8

A tanker is earthed by the use of a conducting strap. The conducting strap is connected to the tanker and trails along the ground. Any electrons that the tanker gains or losses (from its tyres rubbing on the ground) will be able to travel back along the conducting strap, making the tanker neutral again. If this didn?t happen the charge would build up and could produce a spark.

Question 9

Explain some uses of electrostatic charges in everyday objects, such as paint sprayers and insecticides

Answer 9

By giving the paint sprayer a negative charge, the paint is also given a negative charge. When the paint is sprayed because it is all negatively charged the paint droplets repel and this produces a fine mist. The object being sprayed is given the opposite charge and so the paint is attracted to the car ? this can even allow it to bend around corners ? and reach those hard to get to areas.

Question 10

Explain some of the dangers of electrostatics

Answer 10

When a build up of charge occurs it can cause shocks, and produce sparks which can be dangerous when near anything flammable (like petrol).

Question 11

Define ?electric current?

Answer 11

Electric current (symbol ?I?) is the rate of flow of electrons around a circuit, and is measured in Amps (A)

Question 12

What carries the electrical current through a metal wire?

Answer 12

Electrons carry electric current through a wire.

Question 13

Which type of current is supplied by a cell or battery?

Answer 13

A cell or battery supplies direct current.

Question 14

What is the difference between A.C. and D.C.

Answer 14

A.C. stands for alternating current. This is an electric current which travels both directions around a circuit (It does not go both directions at the same time, but alternates between clockwise and anticlockwise). D.C. stands for direct current and only travels one way around the circuit.

Question 15

What does an ammeter measure, and how must it be connected in a circuit.

Answer 15

An ammeter measures the current in a circuit and must be connected in series.

Question 16

What happens to current at a junction

Answer 16

At a junction the current splits, some of it going in each direction.

Question 17

Explain how the current in a circuit depends on the voltage and resistance in the circuit

Answer 17

The equation I=V/R shows that when you double the voltage ? the current doubles. When you double the resistance the current halves.

Question 18

What does a voltmeter measure and how must it be connected in a circuit

Answer 18

A voltmeter measures the voltage across a component and must be placed in parallel

Question 19

Define potential difference/voltage

Answer 19

The potential difference (voltage) is the energy transferred per unit of charge. It is measured in volts or joules per coulomb.

Question 20

Explain how a variable resistor effects the current in the circuit

Answer 20

When a variable resistor is used to increase the resistance the current decreases. When it is used to decrease the resistance the current increases.

Question 21

How does current vary with voltage in a filament lamp?

Answer 21

At higher voltages the bulb will be hotter. This increases the bulbs resistance. If you double the voltage, the current still increases, but it does not double because of the increase in resistance.

Question 22

How does current vary with voltage in a Diode?

Answer 22

As you increase the voltage the current increases. For low voltages the current increases slowly, but for high voltages it increases much more quickly. For negative voltages (this is the same thing as turning the battery around so it?s the other way) no current will flow.

Question 23

How does current vary with voltage in a fixed resistor?

Answer 23

The current increases linearly. If you double the voltage you double the current.

Question 24

How does the resistance of a light-dependent resistor (LDR) change with light intensity

Answer 24

When the light intensity is higher (the light is brighter) the resistance drops, so more current flows. The opposite happens when the light intensity decreases.

Question 25

How does the resistance of a thermistor change with changing temperature

Answer 25

When the temperature is higher (the light is brighter) the resistance drops, so more current flows. The opposite happens when the temperature decreases.

Question 26

Explain why when there is an electrical current in a resistor, there is an energy transfer which heats the resistor ? explain in terms of electrons and ions.

Answer 26

Conducting wires are made of ions, with a ?sea? of electrons moving between them. When you pass a current through the wire the electrons move through the wire in one direction. On their way around the circuit the electrons collide with the ions, and these collisions produce heat.

Question 27

Distinguish between the advantages and disadvantages of the heating effect of an electric current.

Answer 27

In most circuits the heating effect in a circuit is a disadvantage as it means energy is lost to the surroundings. This means that appliances are less efficient and therefore cost more to run. The advantages of this heating effect is that it can be used in kettles or hairdryers for useful purposes.

Question 28

Explain the difference between a vector and a scalar and give examples.

Answer 28

A vector has a size and a direction, examples are: Velocity, Force, Weight, Displacement, Acceleration. Scalars only have a size, examples include: Speed, Distance, Time, Temperature.

Question 29

How do you determine the speed from a distance time graph?

Answer 29

To get the speed you must work out the gradient of the line.

Question 30

Define velocity.

Answer 30

Velocity is speed in a certain direction.

Question 31

How do you calculate the acceleration from a velocity time graph?

Answer 31

Acceleration is found by taking the gradient of a velocity time graph.

Question 32

How do you calculate the distance travelled from a velocity time graph?

Answer 32

The distance travelled is equal to the area under a velocity time graph.

Question 33

What are action and reaction forces?

Answer 33

When two bodies interact, the forces they exert on each other are equal in size and opposite in direction. These are known as action and reaction forces

Question 34

Describe the motion of an object which has zero resultant force acting on it.

Answer 34

An object with no resultant/net force will continue doing whatever it was doing before, i.e. it will keep on travelling at the same speed, or remain stationary.

Question 35

Describe the motion of an object which has a non-zero resultant force acting on it.

Answer 35

An object with a resultant force on it will accelerate in the direction of the force.

Question 36

What two factors affect the acceleration of an object?

Answer 36

The two factors that affect how quickly an object accelerates are the mass of the object and the size of the applied force.

Question 37

Why will a feather and a bowling ball fall at the same speed on the surface of the moon?

Answer 37

All objects accelerate at the same rate when dropped if there is no air resistance

Question 38

Describe the motion of an object falling through the air with reference to its speed, acceleration and the forces acting on it.

Answer 38

When an object falls through the air, air resistance increases with increasing speed. The object accelerates until it is going fast enough for the air resistance to balance the pull of gravity. When the two forces are balanced the object ceases to accelerate and terminal velocity is reached.

Question 39

Define stopping distance

Answer 39

The sum of the thinking and braking distances: The total distance travelled from when a driver first spots a danger, and the car comes to a halt.

Question 40

What affects stopping distance?

Answer 40

The following things will affect stopping distance: a) The mass of the vehicle b) The speed it is travelling at c) The drivers reaction time d) The state of the vehicles brakes e) The state of the road f) The amount of friction between the tyre and the road surface.

Question 41

Define momentum.

Answer 41

Momentum is a vector and it is calculated by multiplying the velocity by the mass. Total momentum is always conserved.

Question 42

How do air bags work?

Answer 42

Air bags (and bubble wrap etc) get squashed when something bumps into them. Because they squash they slow the object down over a larger time. F=(mv-mu)/t So if ?t? is bigger, the force is smaller.

Question 43

What is ?Work done?

Answer 43

Work done = Force x distance moved in the direction of the force, this is equal to the energy transferred.

Question 44

What is ?power?

Answer 44

Power is the rate of doing work, the rate of energy transfer. Power is measured in Watts. One ?Watt? is equal to one joule per second

Question 45

How does braking distance change with speed?

Answer 45

Because E=1/2 mv^2 if you double the speed you quadruple the energy. This means that if a vehicle is travelling twice as fast it will take four times as long to stop.

Question 46

State the principle of conservation of energy.

Answer 46

Energy cannot be created or destroyed, it can only be changed from one type to another.

Question 47

What is the ?atomic/proton? number of an atom

Answer 47

The atomic number tells you how many protons are in the nucleus of an atom

Question 48

What is the ?mass/nucleon? number of an atom

Answer 48

The mass number tells you how many particles in total are in the nucleus of the atom. If you want to work out how many neutrons are in an atom you have to subtract the atomic number from the mass number.

Question 49

What is an ion, and how is it formed?

Answer 49

An ion is an atom that has lost one (or more) electrons; leaving it with an overall charge. Electrons are usually removed by ionising radiation (alpha, beta, gamma, x-rays or ultraviolet).

Question 50

What are Alpha, Beta, and Gamma?

Answer 50

They are ionising forms of radiation emitted from a nucleus. Alpha radiation is a helium nucleus. Beta radiation is an electron. And gamma radiation is an electromagnetic wave.

Question 51

Compare alpha, beta, and gamma, in terms of their ionisation power and their ability to penetrate.

Answer 51

Alpha is the most ionising and the least penetrating (it can be stopped by a sheet of paper or skin). Beta radiation is the second most penetrating and can be stopped by a thin sheet of aluminium. Gamma radiation is the least ionising but the most penetrating and can only be stopped by very thick layers of lead.

Question 52

How can radiation be used as a source of energy.

Answer 52

Nuclear fusion is the energy source of stars. Nuclear fission is the process we use to produce electricity in nuclear power stations. Radioactive decay can also be used to generate heat.

Question 53

Explain how nuclear fission is used to produce energy.

Answer 53

Uranium 235 (an isotope of uranium) will split into two smaller daughter nuclei, giving out two or more neutrons, and energy. This is achieved in a nuclear reactor by slowing down neutrons using a moderator (usually water), these can then be absorbed by the uranium. The two (or more) neutrons released can be used to make other uranium atoms split, this chain reaction can get out of control very quickly ? resulting in a nuclear explosion. To avoid this control rods are used (usually boron) to absorb spare electrons and control the speed of the reaction. If the reaction needs to be slowed the rods are lowered into the reaction chamber where they can absorb more neutrons. If the reaction needs to be speeded up the control rods are raised.

Question 54

How is the heat from a nuclear power station turned into electricity?

Answer 54

The heat generated is used to boil water, turning it into steam, as this steam rises it is used to turn turbines which generate electricity.

Question 55

Why is nuclear waste dangerous.

Answer 55

The products of the nuclear fission (the daughter nuclei) are radioactive, and can therefore cause ionisation which can damage human cells leading to cancer.

Question 56

Describe nuclear fusion.

Answer 56

Nuclear fusion is the creation of larger nuclei from smaller nuclei accompanied by the release of massive amounts of energy. Nuclear fusion is the energy source of stars

Question 57

What is required for nuclear fusion and why?

Answer 57

Nuclear fusion requires very high temperatures and pressures because otherwise the protons in the nucleuses of the atoms will push each other apart, this will stop fusion for happening. Because of these high temperatures and pressures the material has to be held in magnetic fields (because any other substance would melt) and this makes it very difficult to achieve. It also makes it very expensive.

Question 58

What does ?validated by the scientific community mean??

Answer 58

Validation occurs when one group of scientists publishes their results and methodologies. The experiment is then performed by other groups of scientists across the world. If the results of the experiment can be reproduced reliably, the results are said to be ?validated?.

Question 59

Explain the dangers of ionising radiation.

Answer 59

Ionising radiation can remove electrons from atoms. In living cells this can lead to cell death or cell mutation. Mutations can cause cancers.

Question 60

How are people who work with radiation protected from its damaging effects?

Answer 60

a) always handle a source with tongs b)sources should be kept in lead lined containers c) Sources should not be pointed at people d)Always wear gloves e) Always wear eye protection.

Question 61

Describe how, and why, scientists have changed their ideas of the dangers of radiation over time?

Answer 61

Scientists have become more aware of the dangers of radioactivity and now have a deeper understanding of the hazards. Scientists have a better understanding now because the effects of radiation exposure, such as cancers, can take years to manifest. This makes it difficult to associate the cause, and the effect.

Question 62

What are the long term possibilities for storage and disposal of nuclear waste?

Answer 62

Nuclear waste, because of its danger, must be kept away from people. Nuclear waste must be buried deep underground, encased in thick metal, in an area where it is not likely to be disturbed by people, animals or natural phenomenon.

Question 63

Explain the advantages and disadvantages of nuclear power for generating electricity.

Answer 63

The advantages are that nuclear power does not produce any CO2 or SO2 which can lead to global warming or acid rain ? it also produces a large amount of energy. The disadvantages are that there are risks such as that of a catastrophic meltdown, safety issues with handing the fuel etc, it had a negative public perception and it is difficult and costly to dispose of the waste.

Question 64

How does the (radio)activity of a source decrease over time?

Answer 64

Over time the activity of a sample decreases. The samples activity will halve after one ?half-life? has passed. The half life of the material depends on what it is, so all samples of uranium -235 have the same half life, and this will be different from the half life of carbon-14. Activity in measured in Becquerels or Bq for short.

Question 65

Explain what is meant by background radiation and where it comes from.

Answer 65

Background radiation is the constant low level radiation present around us. It comes from certain rocks, radon gas, nuclear medicine, nuclear power stations, cosmic rays, food such as bananas etc. Because the rocks and consequently the amount of radon gas present vary from location to location, the amount of background radiation can also change.

Question 66

What are the everyday uses of nuclear radiation?

Answer 66

Radiation is used in smoke alarms (alpha), irradiating food to kill the bacteria and keep the food fresher for longer (gamma(, sterilising medical equipment(gamma), thickness testing of paper and aluminium(alpha sometimes beta), diagnosis and treatment of cancer(gamma)