Science Summer Holiday Homework Each of you has received your end of year papers back, and you have completed a summary sheet on your performance. Combined Science (4 lessons a week) Combined science students have 1 summary sheet with details of all three AQA papers (biology, chemistry and physics). You have been asked to complete 3 tasks in total of your choice based on your performance. You do not have to do one from each science. Teachers will have given guidance on which ones are best to do. Triple Science (6 lessons a week) Triple science students have 3 summary sheets (1 for each science) with details of the AQA paper and the in-class test on each sheet. You have been asked to complete 2 tasks for each science (6 in total) of your choice based on your performance.
Transcript
Science Summer Holiday Homework
Each of you has received your end of year papers back, and you have
completed a summary sheet on your performance.
Combined Science (4 lessons a week)
Combined science students have 1 summary sheet with details of all three AQA
papers (biology, chemistry and physics). You have been asked to complete 3
tasks in total of your choice based on your performance. You do not have to do
one from each science. Teachers will have given guidance on which ones are
best to do.
Triple Science (6 lessons a week)
Triple science students have 3 summary sheets (1 for each science) with details
of the AQA paper and the in-class test on each sheet. You have been asked to
complete 2 tasks for each science (6 in total) of your choice based on your
performance.
Contents Sheet
Subject Pages
Chemistry 3 - 37
Physics 38 - 74
Biology 75 - 126
How Science Works 127 - 142
Balancing equations help sheet
Chemical reactions show the reactants and products in a reaction. The atoms get
rearranged, but there has to be the same number of each type of atom on both sides of the
arrow, if there is the equation is balanced. This is very important as atoms cannot be created
or destroyed. You can check if an equation is balanced by counting the number of each type
of atom on either side of the arrow – if the numbers are equal the equation is balanced, if
the numbers are not equal the equation is not balanced.
Is the following equation balanced?
1. H2 + O2 H2O
Atom Type Left hand side Right hand side Balanced?
H 2 2 NO
O 2 1
So another oxygen is needed on the right hand side. We cannot simply add a 2 after the H2O to make
H2O2 as this is a whole different chemical, we can only add “big” numbers in front of the element or
compound we are trying to balance.
2. H2 + O2 2H2O
Atom Type Left hand side Right hand side Balanced?
H 2 4 NO
O 2 2
This time the oxygens are balanced but the hydrogen are not, we not need more hydrogen on the
left hand side, we can do this by simply adding a 2 in front of the hydrogen.
3. 2H2 + O2 2H2O
Atom Type Left hand side Right hand side Balanced?
H 4 4 YES
O 2 2
This is now balanced as we have the same number of atoms on both sides of the arrow.
(b) The diagram shows the electronic structure of a magnesium atom. The atomic (proton) number of magnesium is 12.
Magnesium atom
Draw a similar diagram to show the electronic structure of an oxygen atom. The atomic (proton) number of oxygen is 8.
(1)
(c) Magnesium ions and oxide ions are formed when magnesium reacts with oxygen.
The diagram shows the electronic structure of an oxide ion.
Oxide ion
Draw a similar diagram to show the electronic structure of a magnesium ion (1)
(Total 2 marks)
4. Writing chemical formula
The chemical formula of a compound tells you how many atoms of each element the molecule contains.
Formulas of some compounds, with the number of atoms of each element in the molecule
name formula sodium atoms
hydrogen atoms
carbon atoms
sulfur atoms
oxygen atoms
oxygen O2 2
carbon monoxide
CO 1 1
carbon dioxide CO2 1 2
water H2O 2 1
sulfur dioxide SO2 1 2
sulfuric acid H2SO4 2 1 4
sodium carbonate
NaCO3 1 1 3
The small 2 after an element tells you there are two atoms of that particular element in each molecule. For example, the water molecule H2O has two hydrogen atoms. Notice that you do not write a number 1 if there is only one atom of an element in a molecule.
Brackets
Some formulas have brackets in them. For example, sodium hydroxide is NaOH, but magnesium hydroxide is Mg(OH)2. The 2 outside the brackets tells you that you have two of each atom inside the bracket. So in Mg(OH)2 you have one magnesium atom, two oxygen atoms and two hydrogen atoms.
A different example is magnesium chloride. Magnesium forms Mg2+ ions and chlorine forms Cl- ions. So the formula of magnesium chloride is MgCl2. There are 2 chloride ions for every one magnesium ion in the compound.
Try and write the formula for each of the following:
5. Electrolysis:
Electrolysis: splitting a compound using electricity. An electrical circuit is set up with two electrodes
dipped into the electrolyte (the substance that will be broken down):
Ions move toward oppositely charged electrodes When the ions reach the electrodes they lose their charge and become elements. Gases may be
given off during electrolysis – this depends on the compound used and whether it is molten or
dissolved in water.
Ionic compounds can only be electrolysed when they are molten or in solution, as their ions are free
to move and carry a charge.
Half equations are used to represent what is happening at each electrode. For example in the
electrolysis of Lead Bromide:
At the negative electrode: Pb 2+ + 2e- Pb (Lead is reduced)
At the positive electrode: 2Br - Br2 + 2e- (Bromide is oxidised)
When electrolysis happens in water the less reactive element between hydrogen and the metal is
usually produced at the negative electrode. At the positive electrode oxygen gas is often given off
from the hydroxide ions.
Read the pages, complete the test-bite and answer the exam questions below.
Step 2. Write down the relative atomic/formula masses of the reactants and products.
Step 3. Use the balanced equation to write down the ratios of reactants and products.
Step 4. Convert to ratio of reacting masses
Step 5. Calculate the scale factor and apply this to the ratio of reacting masses
Calculate these:
1. If 28 g of iron reacts with copper sulphate solution, what mass of copper will be made?
2. If you have 48 grams of magnesium, what mass of oxygen will react with this?
3. If you have 480 grams of magnesium, what mass of magnesium oxide will be produced?
9. Atomic Structure
Atoms contain three sub-atomic particles called protons, neutrons and electrons. The protons and neutrons are found in the nucleus at the centre of the atom. The nucleus is very much smaller than the atom as a whole. The electrons are arranged in shells around the nucleus. The number of electrons in an atom is always the same as the number of protons, so atoms are
electrically neutral overall.
Atomic number and mass number
The number of protons in the nucleus of an atom is called its atomic number:
the atoms of a particular element all have the same number of protons
the atoms of different elements have different numbers of protons
The total number of protons and neutrons in an atom is called its mass number.
The proton number is shown below the chemical symbol, and the mass number is shown above. In this example the atomic number is 17 and the mass number is 35. This means that each of these atoms has:
17 protons
17 electrons
35 - 17 = 18 neutrons
Identify the number of protons, neutrons and electrons in the following:
Element Protons Neutrons Electrons
Carbon
Helium
Sodium
Gold
Iron
oxygen
10. Impurities
Melting point and boiling point
Impure compounds have a range of melting points and boiling points, as the different substances they contain melt or boil at different temperatures. They may even interfere with each other's melting and boiling points.
Pure compounds have definite melting points and boiling points. The presence of an impurity usually:
Lowers the melting point Raises the boiling point The greater the amount of an impurity, the bigger the differences from the true melting point and boiling point
This is because the impurities interrupt the original structure of the compound so it may result in weaker or fewer bonds.
If a substance does not dissolve in a solvent, we say that it is insoluble. For example, sand does not dissolve in water – it is insoluble. Filtration is a method for separating an insoluble solid from a liquid. When a mixture of sand and water is filtered:
the sand stays behind in the filter paper (it becomes the residue) the water passes through the filter paper (it becomes the filtrate)
The slideshow shows how filtration works:
2. Separating solids from liquids – evaporation
Evaporation is used to separate a soluble solid from a liquid. For example, copper sulfate is soluble in water – its crystals dissolve in water to form copper sulfate solution. During evaporation, the water evaporates away leaving solid copper sulfate crystals behind.
A beaker containing a mixture of insoluble solid and liquid. There
is filter paper in a filter funnel above another beaker.
The mixture of insoluble solid and liquid is poured into the filter
funnel.
The liquid particles are small enough to pass through the filter
paper as a filtrate. The solid particles are too large to pass
through the filter paper and stay behind as a residue.
3. Separating the solvent from a solution – simple distillation
Simple distillation is a method for separating the solvent from a solution. For example, water can be separated from salt solution by simple distillation. This method works because water has a much lower boiling point than salt. When the solution is heated, the water evaporates. It is then cooled and condensed into a separate container. The salt does not evaporate and so it stays behind.
4. Fractional distillation is a method for separating a liquid from a mixture of two or more liquids. For example,
liquid ethanol can be separated from a mixture of ethanol and water by fractional distillation. This method
works because the liquids in the mixture have different boiling points. When the mixture is heated, one liquid
evaporates before the other.
Salt solution is heated.
Water evaporates and its vapours rise. The
water vapour passes into the condenser,
where it cools and condenses. Liquid water
drips into a beaker.
All the water has evaporated from the salt
solution, leaving the salt behind
A water and ethanol mixture is heated in a
flask using an electric heater. Vapour forms
in the air above the mixture in the flask
The boiling point of ethanol is 78°C. Ethanol
vapour passes into the condenser, where it is
cooled and condensed. Liquid ethanol drips
into a beaker.
When most of the ethanol has left, water
vapour at 100°C passes into the condenser,
where it is cooled and condensed. Liquid
water now drips into the beaker.
5. Separating dissolved solids – chromatography
Paper chromatography is a method for separating dissolved substances from one another. It is often used when the dissolved substances are coloured, such as inks, food colourings and plant dyes. It works because some of the coloured substances dissolve in the solvent used better than others, so
they travel further up the paper.
A pencil line is drawn, and spots of ink or plant dye
are placed on it. There is a container of solvent,
such as water or ethanol.
The paper is lowered into the solvent. The solvent
travels up through the paper, taking some of the
coloured substances with it.
As the solvent continues to travel up the paper,
the different coloured substances spread apart. In
this example, the colours separated substances
are yellow, red and black.
Exam questions to try:
1. Crude oil is the source of many useful materials. Crude oil is separated into fractions by fractional
distillation.
Describe how the naphtha fraction separates from the other fractions.
2. Read the article and then answer the questions that follow.
Nanotennis!
Tennis balls contain air under pressure, which gives them their bounce. Normal tennis balls are changed at regular intervals during tennis matches because they slowly lose some of the air. This means that a large number of balls are needed for a tennis tournament, using up a lot of materials.
‘Nanocoated’ tennis balls have a ‘nanosize’ layer of butyl rubber. This layer slows down the escape of air so that the ball does not lose its pressure as quickly. The ‘nanocoated’ tennis balls last much longer and do not need to be replaced as often.
(a) How does the ‘nanosize’ layer make the tennis balls last longer?
15. Isotopes are atoms of an element with the normal number of protons and electrons, but different numbers of neutrons. Isotopes have the same atomic number, but different mass numbers.
The different isotopes of an element have identical chemical properties. However, some isotopes are radioactive.
Isotopes of hydrogen
Most hydrogen atoms consist of just one proton and one electron, but some also have one or two neutrons.
Isotopes of hydrogen
Isotope Protons Electrons Neutrons
1 1 1 - 1 = 0
1 1 2 - 1 = 1
1 1 3 - 1 = 2
Isotopes of chlorine
Chlorine atoms contain 17 protons and 17 electrons. About 75 per cent of chlorine atoms have 18 neutrons, while about 25 per cent have 20 neutrons.
Isotopes of chlorine
Isotope Protons Electrons Neutrons
17 17 35 - 17 = 18
17 17 37 - 17 = 20
Chlorine's Ar of 35.5 is an average of the masses of the different isotopes of chlorine. This is calculated by working out the relative abundance of each isotope. For example, in any sample of Chlorine 25% will be 37Cl and 75% 35Cl. The relative atomic mass is therefore calculated using the equation:
(% of isotope 1 × mass of isotope 1) + (% of isotope 2 × mass of isotope 2) ÷ 100
So in the case of chlorine:
(75 × 35) + (25 × 37)∕100
= 2625 + 925
∕100
= 35.3
Try the testbite below:
http://www.bbc.co.uk/bitesize/quiz/q29479739
16. Plum pudding model:
Plum pudding model of the atom
An early model - scientific idea - about the structure of the atom was called the plum pudding model. In this model, the atom was imagined to be a sphere of positive charge with negatively charged electrons dotted around inside it like plums in a pudding. Scientific models can be tested to see if they are wrong by doing experiments. An experiment carried out in 1905 showed that the plum pudding model could not be correct.
Rutherford’s scattering experiment
A scientist called Rutherford designed an experiment to test the plum pudding model. It was carried out by his assistants Geiger and Marsden. A beam of alpha particles was aimed at very thin gold foil and their passage through the foil detected. The scientists expected the alpha particles to pass straight through the foil, but something else also happened.
Some of the alpha particles emerged from the foil at different angles, and some even came straight back. The scientists realised that the positively charged alpha particles were being repelled and deflected by a tiny concentration of positive charge in the atom. As a result of this experiment, the plum pudding model was replaced by the nuclear model of the atom.
Try the exam question below:
2. In the early part of the 20th century, scientists used the ‘plum pudding’ model to explain the structure of the atom.
Following work by Rutherford and Marsden, a new model of the atom, called the ‘nuclear’ model, was suggested.
(a) Describe the differences between the two models of the atom.
Work done = .................................................. J (2)
(ii) It takes the climber 800 seconds to climb to the top of the cliff. During this time the energy transferred to the climber equals the work done by the climber.
Calculate the power of the climber during the climb.
Total resistance of X and Y = ........................................... Ω (2)
(Total 8 marks)
Hint: read the key
points at the top
Specific Heat Capacity task
Read through the revision information then complete the exam questions at the end.
Temperature and heat are not the same thing:
temperature is a measure of how hot something is heat is a measure of the thermal energy contained in an object.
Temperature is measured in °C, and heat is measured in J. When heat energy is transferred to an object, its temperature increase depends upon the:
the mass of the object the substance the object is made from the amount energy transferred to the object.
For a particular object, the more heat energy transferred to it, the greater its temperature increase.
Specific heat capacity
The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1°C. Different substances have different specific heat capacities. The table shows some examples.
Heat capacities of different substances
Substance Specific heat capacity in J / kg °C
water 4181
oxygen 918
lead 128
Notice that water has a particularly high specific heat capacity. This makes water useful for storing heat energy, and for transporting it around the home using central heating pipes.
Calculating specific heat capacity
Here is the equation relating energy to specific heat capacity:
E = m × c × θ
E is the energy transferred in joules, J m is the mass of the substances in kg c is the specific heat capacity in J / kg °C θ (‘theta’) is the temperature change in degrees Celsius, °C
For example, how much energy must be transferred to raise the temperature of 2 kg of water from 20°C to 30°C?
E = m × c × θ (θ = 30 – 20 = 10°C)
E = 2 × 4181 × 10 = 83,620 J or 83.62 kJ
Q1.The electric kettle shown below is used to boil water.
(a) After the water has boiled, the temperature of the water decreases by 22 °C. The mass of water in the kettle is 0.50 kg. The specific heat capacity of water is 4200 J/kg °C.
Calculate the energy transferred to the surroundings from the water.
(b) Why is the total energy input to the kettle higher than the energy used to heat the water?
Tick (✔) one box.
Tick (✔)
Energy is absorbed from the surroundings.
Energy is used to heat the kettle.
The kettle is more than 100% efficient.
(1) (Total 3 marks)
Q2.A ‘can-chiller’ is used to make a can of drink colder.
(a) The can-chiller decreases the temperature of the liquid in the can by 15 °C. The mass of liquid is 0.33 kg. The specific heat capacity of the liquid is 4200 J / kg °C.
Calculate the energy transferred from the liquid as it cools.
Energy = ................................................. J (2)
(b) Complete the following sentence.
The specific heat capacity of a substance is the amount of energy required to change the ............................................................. of one kilogram of the substance by one degree Celsius.
(1)
(c) To calculate the specific heat capacity of a material, the mass of the material needs to be measured. State the name of a measuring instrument used to measure mass.
(d) The back of the can-chiller has cooling fins, as shown in Figure 2.
The cooling fins increase the rate of energy transfer from the can-chiller to the surroundings.
Complete the following sentences.
The cooling fins are a ................................... colour because that makes them good emitters of infrared radiation. The large surface area of the cooling fins allows the air around the can-chiller to gain energy quickly and rise, transferring energy by ................................... .
(2)
(e) (i) The energy input to the can-chiller is the same as the energy output. This shows that energy is conserved.
Complete the following sentence.
Energy can be transferred usefully, stored or dissipated, but cannot be ................................. or destroyed.
(1)
(ii) The temperature of the can of drink decreases while it is in the can-chiller.
What happens to the temperature of the air around the cooling fins?
Q3.A new design for a kettle is made from two layers of plastic separated by a vacuum. After the water in the kettle has boiled, the water stays hot for at least 2 hours.
The new kettle is shown below.
(a) The energy transferred from the water in the kettle to the surroundings in 2 hours is 46 200 J.
The mass of water in the kettle is 0.50 kg.
The specific heat capacity of water is 4200 J/kg °C.
The initial temperature of the water is 100 °C.
Calculate the temperature of the water in the kettle after 2 hours.
Read through the revision information then complete the exam questions at the end.
Hooke's Law, elastic and plastic behaviour
(Note: Plastic behaviour is sometimes called inelastic behaviour.)
In the 1600s, a scientist called Robert Hooke discovered a law for elastic materials.
An elastic material is one that will return to its original shape when the force applied to it is taken away.
A plastic (or inelastic) material is one that stays deformed after you have taken the force away.
If you apply too big a force a material will lose its elasticity.
Hooke discovered that the amount a spring stretches is proportional to the amount of force applied to it. This means if you double the force its extension will double, if you triple the force the extension will triple and so on.
The elastic limit can be seen on the graph. This is where the graph stops being a straight line. If you stretch the spring beyond this point it will not return to its original shape.
You can write Hooke's law as an equation:
F = kx
where:
F is the applied force (in newtons, N), x is the extension (in metres, m) and k is the spring constant (in N/m).
The spring constant measures how stiff the spring is. The larger the spring constant the stiffer the spring. You may be able to see this by looking at the graphs below:
Elastic behaviour is very important in car safety, as car seatbelts are made from elastic materials. However, after a crash they must be replaced as they will go past their elastic limit.
Q1.A student suspended a spring from a laboratory stand and then hung a weight from the spring.
Figure 1 shows the spring before and after the weight is added.
Figure 1
(a) Which distance gives the extension of the spring?
Tick one box.
from J to K
from K to L
from J to L
(1)
(b) The student used the spring, a set of weights and a ruler to investigate how the extension of the spring depended on the weight hanging from the spring.
Figure 2 shows that the ruler is in a tilted position and not upright as it should be.
Figure 2
How would leaving the ruler tilted affect the weight and extension data to be recorded by the student?
Use answers from the box to complete each sentence.
Each answer may be used once, more than once or not at all.
greater than the same as smaller than
The weight recorded by the student would be .......................................... the actual weight.
The extension recorded by the student would be .......................................... the actual weight.
(2)
(c) The student moves the ruler so that it is upright and not tilted.
The student then completed the investigation and plotted the data taken in a graph.
The student’s graph is shown in Figure 3.
Figure 3
Use Figure 3 to determine the additional force needed to increase the extension of the spring from 5cm to 15cm.
Additional force = ............................................ N (1)
(d) What can you conclude from Figure 3 about the limit of proportionality of the spring?
……………………………………………………………………………………………
……………………………………………………………………………………………
…………………………………………………………………………………………...
(1)
(e) The student repeated the investigation with three more springs, K, L and M.
The results for these springs are given in Figure 4.
Figure 4
All three springs show the same relationship between the weight and extension.
What is that relationship?
Tick one box.
The extension increases non-linearly with the increasing weight.
The extension is inversely proportional to the weight.
The extension is directly proportional to the weight.
(1)
(f) Which statement, A, B or C, should be used to complete the sentence?
Write the correct letter, A, B or C, in the box below.
A a lower spring constant than
B the same spring constant as
C a greater spring constant than
From Figure 4 it can be concluded that spring M has the other two springs.
(1) (Total 7 marks)
Q2. A student investigated how the extension of a spring depends on the force applied to the spring.
The diagram shows the spring before and after a force had been applied.
(a) (i) Complete the following sentence using letters, A, B, C or D, from the diagram.
The extension of the spring is the distance between the positions labelled
......................and ...................... on the metre rule. (1)
(ii) What form of energy is stored in the stretched spring?
Q1.(a) A person cut his finger. A small amount of blood flowed from the cut but soon stopped due to blood clotting. The following sentences describe what happens when a person has a small cut and a blood clot is formed.
Draw a ring around the correct answer to complete each sentence.
(i) The tiny blood vessels near the surface of the skin that are damaged
are
arteries.
capillaries.
veins.
(ii) Blood clotting is stimulated by
platelets.
red blood cells.
white blood cells.
(iii) During blood clotting fibrinogen changes to fibrin.
haemoglobin changes to oxyhaemoglobin.
lipid changes to fatty acids.
(ii) Red blood cells have a diameter of about 8 micrometres. Some capillaries have an internal diameter of about 10 micrometres. Red blood cells, with antibodies bound to them, stick together. B antigens are found on the surface of red blood cells in people who have blood group B.
Use this information to explain why transfusion of group B blood into a person of blood group A is unsafe.
(b) Red blood cells contain haemoglobin. Explain how this enables red blood cells to pick up oxygen from the alveoli and release it to cells in other parts of the body.
Q3. Capillaries are blood vessels in the body which join the arteries to the veins. They have walls which are one cell thick and so are able to exchange substances with the body cells.
(i) Name two substances that travel from the muscle cells to the blood in the capillaries.
(ii) The flagellum helps the cell to move through water. Scientists think that the flagellum and the light-sensitive spot work together to increase photosynthesis. Suggest how this might happen.
(d) Multicellular organisms often have complex structures, such as lungs, for gas exchange. Explain why single-celled organisms, like algae, do not need complex structures for gas exchange.
Q5.(a) The diagrams show the structures of a yeast cell and a bacterial cell.
(i) Both the yeast cell and the bacterial cell have structures A and B.
Name structures A and B.
A .......................................................
B .......................................................(2)
(ii) The yeast cell and the bacterial cell have different shapes and sizes. Give one other way in which the structure of the bacterial cell is different from the structure of the yeast cell.
Q6. The diagram shows a human sperm. Inside the tail of the sperm is a filament mechanism that causes the side to side movement of the tail, which moves the sperm.
(a) Describe the function of the mitochondria and suggest a reason why they are arranged around the filament near the tail of the sperm.
(d) Draw one line from each digestive enzyme to the correct breakdown product.
Digestive enzyme Breakdown products
amino acids.
Amylase breaks down starch into……
bases.
Lipase breaks down fats into…
fatty acids and
glycerol.
Protease breaks down proteins into…
sugars.
(3) (Total 8 marks)
Q2.Some students investigated the effect of pH on the digestion of boiled egg white by an enzyme called pepsin. Egg white contains protein. The students:
• put a glass tube containing boiled egg white into a test tube
• added a solution containing pepsin at pH 7
• set up six more tubes with solutions of pepsin at different pH values
• left the test tubes for 24 hours at room temperature.
The image below shows one of the test tubes, at the start and at the end of the 24 hours.
(ii) What type of enzyme digests protein? Tick ( ) one box.
amylase
lipase
protease
(1)
(b) The egg white in each tube was 50 mm long at the start of the investigation. The table below shows the students’ results.
pH Length in mm of boiled egg white after 24 hours
1 38
2 20
3 34
4 45
5 50
6 50
7 50
(i) At which pH did the pepsin work best? pH ..................................(1)
(ii) The answer you gave in part (b)(i) may not be the exact pH at which pepsin works best. What could the students do to find a more accurate value for this pH?
Q3.Fresh milk is a mixture of compounds including lipid, protein and about 5% lactose sugar. Lactose must be digested by the enzyme lactase, before the products can be absorbed. Lactase can be added to fresh milk to pre-digest the lactose. This makes ‘lactose-free’ milk, which is suitable for people who do not produce enough lactase of their own. A student investigated the effect of changing pH and temperature on the digestion of lactose in milk.
The results are shown in Tables 1 and 2.
Table 1
Effect of pH
Table 2 Effect of temperature
pH Time taken to
digest lactose in minutes
Temperature
in °C
Time taken to digest lactose in
minutes
4.0 20 25 20
5.0 18 30 14
6.0 13 35 11
7.0 7 40 6
8.0 5 45 29
9.0 6 50 No digestion
(a) The label on a carton of lactose-free milk states: ‘Lactase is normally produced in the stomach of mammals.’ The results in Table 1 suggest that this statement is not true. Explain how.
Q2.The diagram in Figure 1 shows a section through the human heart, seen from the front.
Figure 1
(a) Draw a ring around the correct answer to complete each sentence.
(i) The wall of the heart is made mostly of
epithelial
glandular
muscular
tissue.
(ii) The resting heart rate is controlled by the pacemaker.
The pacemaker is located at position
1.
6.
7.
(iii) If a person’s heart rate is irregular, the person may be fitted with an artificial pacemaker.
The artificial pacemaker is
an electrical device.
a pump.
a valve.
(b) (i) Write a number, 2, 5, 6 or 7, in each of the three boxes to answer this question.
Which chamber of the heart:
pumps oxygenated blood to the head and body
receives deoxygenated blood from the head and body
receives oxygenated blood from the lungs?
(ii) Give the number, 3, 4 or 8, of the valve that closes when the blood pressure in the aorta is greater than the blood pressure in the left ventricle.
Write the correct answer in the box.
(c) The diagram in Figure 2 shows one type of artificial heart valve. The plastic ball is in the closed position.
Figure 2
This type of artificial valve could be used to replace a faulty valve in the heart.
(ii) The artificial valve could be used to replace valve 4 shown in Figure 1. The artificial valve opens to let blood through when the ball is moved towards A. Which end of the valve, A or B, should point towards chamber 5? Explain your answer.
Replacing a damaged heart valve can dramatically improve the blood circulation and the supply of oxygen to the body’s tissues. The operation to replace a heart valve is a long one during which the patient’s blood goes through a bypass machine. Sometimes the artificial valve can fail to work. If the surface of the valve becomes rough, small blood clots can form on its surface then break away and be carried around the body by the blood.
Evaluate the advantages and disadvantages of artificial heart valves.
Q3. A student pedalled an exercise cycle at constant speed for 5 minutes. The student’s heart rate was recorded at one-minute intervals during the exercise and also during recovery. The results are shown in the graph.
(a) Describe, in as much detail as you can, the changes in heart rate between 0 and 14 minutes.
Q1.(a) In humans there are two types of cell division: mitosis and meiosis. The table below gives statements about cell division. Tick ( ) one box in each row to show if the statement is true for mitosis only, for meiosis only, or for both mitosis and meiosis. The first row has been done for you.
Statement Mitosis only Meiosis only Both mitosis and meiosis
How cells are replaced
How gametes are made
How a fertilised egg undergoes cell division
How copies of the genetic information are made
How genetically identical cells are produced
(4)
(b) Stem cells can be taken from human embryos. In therapeutic cloning, an embryo is produced that has the same genes as the patient.
(i) Name one source of human stem cells, other than human embryos.
(ii) Stem cells from embryos can be transplanted into patients for medical treatment. Give one advantage of using stem cells from embryos, compared with cells from the source you named in part (i).
(c) A student wanted to find out more about the cell cycle. The student made a slide of an onion root tip. She counted the number of cells in each stage of the cell cycle in one field of view. The table below shows the results.
(d) The cell cycle in an onion root tip cell takes 16 hours. Calculate the length of time Stage 2 lasts in a typical cell. Give your answer to 2 significant figures.
The development of monoclonal antibodies has provided society with the
power and opportunity to treat diseases. However with this power and
opportunity comes responsibility. The use of monoclonal antibodies raises
some ethical issues.
- Production involves the use of mice. These mice are used to produce both antibodies and tumour cells. The production of tumour cells involves deliberately inducing cancer in mice. Despite specific guidelines drawn up to minimise any suffering, some people still have reservations about using animals in this way.
- To eliminate the need for humanisation of the antibody, transgenic mice can be used. In this case, a human gene is placed in the mice to that they can produce human antibodies rather than mouse antibodies. This raises the whole debate surrounding the ethics of genetic engineering.
- Monoclonal antibodies have been used successfully to treat a number of diseases, including cancer and diabetes, saving many lives. There have also been some deaths associated with their use in the treatment of multiple sclerosis.
- Testing for the safety of new drugs presents certain dangers. In march 2006, six healthy volunteers took part in the trial of new monoclonal antibody (TGN1412) in London. Within minutes they suffered multiple organ failure, probably as a result of T cells overproducing chemicals that stimulate an immune response or attacking the body tissues. All the volunteers survived, but it raises issues about the conduct of drug trials. (Link to topic 3.11)
Society must use the issues raised here, combined with current scientific
knowledge about monoclonal antibodies, to make decisions about their
production and use. We must balance the advantages that a new medicine
provides with the dangers that its production and use might bring. Only then
can we make informed decisions at an individual, local, national, and global
level about the ethical use of drugs such as monoclonal antibodies.
Q1. Another way to eliminate the need for humanisation would be to inject humans
with an antigen and then extract the antibodies produced to it. Suggest reasons why
this is considered unethical.
Q2. Should trials be limited to volunteers who are terminally ill with a condition that
they monoclonal antibody is designed to treat?
Q1.Monoclonal antibodies are used to measure the levels of hormones in the blood.
Pregnant women produce the hormone HCG.
HCG is excreted in urine.
Figure 1 shows four pregnancy test strips.
Figure 1
(a) Which test strip shows a negative test result?
Tick one box.
A
B
C
D
(1)
(b) Monoclonal antibodies are used for pregnancy testing.
Q6.The human body is organised to carry out many different functions.
(a) Use words from the box to complete Figure 1 by putting the parts of the body in order of size from smallest to largest. The smallest one has been done for you.
(2)
(b) The stomach is made of different types of tissue. Draw one line from each type of stomach tissue to the correct description.
(3)
Movement of Particles
Diffusion (osmosis and active transport) is another area that is highly likely to appear somewhere in
the paper as it can be a whole question by itself, or it could be linked to specialised cells, organ
systems (digestive, respiratory and circulatory), adaptation, homeostasis and plant systems.
Therefore it is essential you know the difference! Read the information on the following link and
Describe how ions, water and sugar are obtained and transported through plants. In your answer you should refer to materials moving upwards in a plant and to materials moving downwards in a plant.
Q2.In this question you will be assessed on using good English, organising information clearly and
using specialist terms where appropriate.
Diffusion is an important process in animals and plants. The movement of many substances into and out of cells occurs by diffusion. Describe why diffusion is important to animals and plants.
b) Calculate the speed of the tractor between 0 and 16 seconds
2) A solution of starch and amylase was placed in a water bath at 40% for 20 minutes. After
this time the solution was testing with a colorimeter to see how much light passed through.
After 20 minutes the percentage of light passing through the solution was 32%. At what rate
had the sugar been produced by the breakdown of starch by amylase?
3) Use the graph below, to calculate the mean rate of the reaction up until the point at
which the reaction is complete. Record your answer to three significant figures.
Answer:
The word significant means: having meaning.
With the number 368249, the 3 is the most significant digit, because it tells us that the
number is 3 hundred thousand and something. It follows that the 6 is the next most
significant, and so on.
With the number 0.0000058763, the 5 is the most significant digit, because it tells us
that the number is 5 millionths and something. The 8 is the next most significant,
and so on.
Be careful however with numbers such as 30245, the 3 is the first significant figure and
0 the second, because of its value as a place holder.
To calculate percentage change you need to:
1. To calculate percentage change (increase or decrease):
o Calculate the difference between the two numbers being compared:
Difference = New Number - Original Number
o Divide the difference by the original number and multiply the result by 100:
Percentage Change = Difference ÷ Original Number × 100
If the final answer is a negative number it is a percentage decrease, otherwise, it is a
percentage increase.
12. Graph drawing
Bar charts are marked out of 4 – the marks
are awarded for:
Suitable scale, labels and units on y axis
Bars all the same width
Accurate drawing of the bars
Bars labelled on the x axis
Line graphs are marked out of 4 – the marks
are awarded for:
X axis scale, labels and units
Y axis scale, labels and units
Accurate plots
Line of best fit
Drawing Graphs
Presenting information When asked to take information from a table and present it in the form of a graph you need to decide if it should be a line or a bar graph. If you are not told in the exam follow the rule: if you are given two sets of numbers then make a line graph.
Use the column headings from the table as the axis labels. Remember to include the units as well.
The variable that has been altered goes on the x axis and the variable that has been obtained goes on the y axis.
Pick a suitable scale. The graph should cover at least 50% of the paper and it should start at 0 and increase in equal increments, ie each box should be worth the same value.
On a line graph plot the points using a lightly-drawn X and join them with a ruler. Ensure you don't extend the line before or beyond the first and final points given in the table, eg do not plot a 0 value unless it is given in the table.
On a bar graph the bars should be of equal width. If you are plotting two sets of data you should distinguish between them by shading bars and including a key.
Graphs and charts (data interpretation)
Read the x and y axes carefully to:
check the variables note the units used calculate the division on the scale
To decide which is the best scale for your axes, you need to divide the range of your variable
by the number of squares you have. For example if your data ranges from 0 to 15 and you
have 25 lines available you divide 15 by 25, this equals 0.6
so you round up to 1 so every square = 1. If data ranges
from 0 to 10 and you have 36 squares available then 10/36
= 0.28 so round to 0.5 so 1 = 2 squares.
You can however use an axis break to show you are not
starting at 0.
Lines of best fit: In science unlike
From the graph you should be able to:
read any value accurately calculate an increase calculate a decrease add up a total make predictions describe and explain trends
in maths lines of best fit do not have to be a straight line, they do not have to be straight
lines. They can be (and often are) CURVES, and can also be positive or negative correlation.
See below for examples of different graphs in science.
Now draw three graphs using the different tables below, each one will be a little more
difficult. It appears that the way marks are awarded in the new specification for graphs are
1) axis/axes drawn using sensible scale (this doesn’t just mean one that fits on the
paper, it must also allow for easy plotting), the scale must also go up in equal
intervals (not just in the numbers that appear in the table
2) for most of data plotted accurately (within half a square)
3) all of data plotted accurately
4) line of best fit (both correct, and smooth, this is why you MUST do it in pencil so you
can rub out any sketchy bits)
Points to note: this will be a negative correlation (line will go down), and watch the x axis
(age) as the values in the table do not go up equally so don’t just plot the numbers above!
Points to note: like many graphs in all sciences, but particularly chemistry, this graph will
level out.
Points to note: you will need to go below 0 on the y axis for this graph!
Exam Skills- Evaluating
Students should use the information supplied as well as their knowledge and understanding to
consider evidence for and against. An evaluation goes further than ‘compare’. For example, they
may be given a passage to read and told to ‘Evaluate the benefits of using system x and system y’.
This means they will need to write down some of the points for and against both systems to develop
an argument. A mark may also be available for a clear and justified conclusion.
When giving comparisons students should be encouraged to compare both sides using linking words.
Useful words for students to use could be ’however’, ‘whereas’ ‘but’ and ’on the other hand’.
No credit will be given just for giving the information stated directly from the question in either the
comparisons or in the conclusion.
Example: Biology Read the information about the trialling of the first contraceptive pill. Evaluate the issues involved with methods used by Pincus in trialling the contraceptive pill. Do you think he should have carried out this trial?
In this question you are required to understand the text and select some positive and some negative things about the way the trial was conducted, include some of your own knowledge on drugs testing and the give your own conclusion based on the arguments you have made. In a recent science conference AQA advised students to answer in bullet points to keep answers precise, scientific and allow students to identify more easily points they have made. Exemplar answer
This trial involved large numbers so that would have given valid results.
It was also a good trial of the general population because if poor uneducated
women could make it work it would be reliable. However, the trial was not very
ethical by today’s standards because we don’t know that the women gave
informed consent.
They were not told it was experimental or that there could be side effects.
The trial was not well designed as there was no placebo control group and they
did not do pre-trials to find the best dose and check for side effects.
Overall, I believe that this was an unethical trial and therefore should not have
been carried out. (6 marks)
The Pill was developed by a team of scientists led by Gregory Pincus. The team needed to carry out large scale trials on humans. In the summer of 1955, Pincus visited the island of Puerto Rico. Puerto Rico is one of the most densely populated areas in the world. Officials supported birth control as a form of population control. The women in Puerto Rico were mainly poor and uneducated. The scientists selected a pill with a high dose of hormones. The Pill was found to be 100% effective when taken properly. But 17% of the women in the study complained of side effects. The women in the trial had been told only that they were taking a drug that prevented pregnancy. They had
not been told that the Pill was experimental or that there was a chance of dangerous side effects.
Words highlighted in pink are good words to use that have allowed for the answer to flow and score marks for construction of argument. Words highlighted in yellow are examples of good scientific terminology. Remember:
1. Never simply copy whole statements provided by the exam, quote them but add
to them, explaining why you think the statement is a positive or a negative.
2. Try to balance your statements, state something positive followed by however,
or nevertheless etc before contrasting with a negative point.
3. Even if the question doesn’t clearly ask for a conclusion give one, it takes less
than a minute to write and will never cause you to lose a mark but might help you
gain one!
4. Remember to include some of your own knowledge too to boost your answer into
the level 2/3 response (dependent on whether the question is out of 4 or 6
marks)
Below is an example of what is meant by “level”. In mark schemes examiners read your
answer and first determine the general feel for the answer and which “level” it fits,
before then looking at the quality of the scientific response and the mark within the
level.
Now try the questions below.
Q1.LDL is one form of cholesterol found in the blood. People with a high concentration of LDL in their blood may be treated with drugs called statins. A high concentration of LDL cholesterol in the blood may result in an increased risk of heart and circulatory diseases. The graph shows the effects of the treatment of one person with four different statins, A, B, C and D, over a period of 8 years. The arrows show when each new treatment was started.
Each treatment was continued until the next treatment was started.
Year
Compare the effectiveness of the five treatments in reducing the risk of heart and circulatory diseases for this person.
(b) People can be treated for cardiovascular diseases with statins or aspirin. Information about these two drugs is given in the table.
STATINS ASPIRIN
Statins are only available on prescription from doctors.
Aspirin can be bought over the counter. Treatment with aspirin costs up to £15 per year.
In studies, 30 000 patients were monitored over several years. Statins were found to reduce the rate of non-fatal heart attacks by about 30%.
In a study of 1000 patients, aspirin was found to cause bleeding of the stomach in around 0.5% of patients and there was a slightly increased risk of poor blood clotting at cuts.
Approximately 0.1% of the patients suffered serious muscle damage and 0.01% suffered kidney failure.
There was a slightly increased risk of damage to the blood vessels in the brain in older patients.
Statins reduce blood cholesterol which builds up in the walls of blood vessels. The cost of treating patients with statins can vary between £150 and £500 per year, depending on the type of cardiovascular disease being treated.
Aspirin was found to reduce the risk of non-fatal heart attacks by 31%.
Would you recommend statins or aspirin for the treatment of cardiovascular diseases? In your answer you should:
• give your recommendation
• use information from the table to support your recommendation by making comparisons of the two drugs.
Q3. Copper was considered to be the most suitable material to use for hot water pipes.
PEX is now used as an alternative material for hot water pipes.
Copper is extracted from its ore by a series of processes.
1 The low-grade ore is powdered and concentrated.
2 Smelting is carried out in an oxygen flash furnace. This furnace is heated to
1100 °C using a hydrocarbon fuel. The copper ore is blown into the furnace
with air, producing impure, molten copper.
3 Oxygen is blown into the impure, molten copper to remove any sulfur. The
copper is cast into rectangular slabs.
4 The final purification of copper is done by electrolysis.
PEX is made from crude oil by a series of processes.
1 Fractional distillation
2 Cracking
3 Polymerisation
4 Conversion of poly(ethene) into PEX
Suggest the possible environmental advantages of using PEX instead of copper for hot
water pipes.
Please answer on separate paper.
Q4. The extract below was taken from a leaflet on the uses of platinum. One of the uses described was in making electrodes for spark plugs in car engines. The spark plug produces the spark which ignites the fuel in the engine.
Spark Plugs
The electrodes in a spark plug have to conduct electricity very well. Since they project into the combustion chamber of the engine, they must also be able to withstand extremely high temperatures in a very corrosive atmosphere.
Nickel-based plugs have been produced for many years. They only last a fairly short time. As the electrodes wear, combustion becomes less efficient and the petrol is not burnt completely.
Platinum and other precious metals can now be used in spark plugs. These last much longer and are more efficient. This can help to reduce air pollution.
The table below gives some information about platinum and nickel.
MELTING POINT (° C)
BOILING POINT (° C)
POSITION IN REACTIVITY
SERIES
COST (£/kg)
nickel 1455 2920 Higher than gold
2.5
platinum 1769 4107 below gold 6110
(a) Compare nickel and platinum for use in making the electrodes in spark plugs.
A good answer should give advantages and disadvantages of each metal linking these to the properties of the metals. Marks will be given for the way in which you organise your answer.
