Year 10 Paper 4: Combined Practice
Covers cell biology, atomic structure, bonding, energy and electricity.
Year 10 here means a typical teaching order, not a syllabus rule. No exam board defines what belongs to Year 10, and schools sequence the course differently. Check it against your own scheme of work before using it to decide what a class has covered.
Questions
Question 1 [4 marks]
Atomic Structure and the Periodic Table
Chlorine has two naturally occurring isotopes: chlorine-35, with an abundance of 75%, and chlorine-37, with an abundance of 25%.
Calculate the relative atomic mass of chlorine. Give your answer to 1 decimal place.
Question 2 [4 marks]
Energy
A crane lifts a load of mass 250 kg through a height of 12 m.
Calculate the gravitational potential energy gained by the load. Use GPE = m g h, with g = 9.8 N/kg.
Question 3 [4 marks]
Cell Biology
A student views a cheek cell using a light microscope. The actual width of the cell is 0.05 mm. The width of the cell in the micrograph image is 20 mm.
Calculate the magnification of the image. Use magnification = image size / actual size.
Question 4 [5 marks]
Bonding, Structure and the Properties of Matter
A sample of poly(ethene) contains chains that are, on average, made from 500 repeating -CH2-CH2- monomer units.
The relative formula mass of one -CH2-CH2- unit is 28.
Calculate the average relative molecular mass of a poly(ethene) chain in this sample, and explain why this value is described as an average.
Question 5 [5 marks]
Electricity
Two resistors, of resistance 15 ohms and 25 ohms, are connected in series with a 20 V supply.
Calculate the current flowing in the circuit, and calculate the potential difference across the 15 ohm resistor.
Question 6 [5 marks]
Bonding, Structure and the Properties of Matter
Iodine is a simple molecular substance. Silicon dioxide has a giant covalent structure. Both substances contain strong covalent bonds.
Explain why iodine has a much lower melting point than silicon dioxide.
Question 7 [6 marks]
Energy
An electric heater with a power of 1.5 kW is used to heat 2.0 kg of water. The specific heat capacity of water is 4200 J/kg degrees C.
Calculate the energy transferred by the heater in 4 minutes, and calculate the resulting temperature rise of the water, assuming all the energy is usefully transferred to the water. Use energy = power x time and change in thermal energy = m c (change in temperature).
Question 8 [6 marks]
Atomic Structure and the Periodic Table
An ion of an element has the electronic structure 2,8 and an overall charge of 2+.
Deduce the atomic number of this element, state its identity, and state the group of the periodic table it belongs to.
Question 9 [6 marks]
Cell Biology
A potato chip is placed in distilled water.
Water moves into the chip by osmosis, increasing its mass by 8% over 24 hours.
The mass of the chip after 24 hours is 5.94 g.
Calculate the original mass of the potato chip before it was placed in the water, and explain why the chip gained mass.
Question 10 [6 marks]
Energy
A 1.5 kg block of an unknown metal is heated from 20 degrees C to 95 degrees C using 87750 J of energy.
Calculate the specific heat capacity of the metal, in J/kg degrees C. Use change in thermal energy = m c (change in temperature).
Question 11 [6 marks]
Atomic Structure and the Periodic Table
Group 7 of the periodic table contains the halogens, which react by gaining one electron to form a negative ion.
Explain, in terms of electronic structure, why reactivity decreases going down Group 7 of the periodic table.
Question 12 [6 marks]
Energy
A washing machine motor is supplied with 1500 J of energy each cycle.
Of this, 1050 J is usefully transferred to kinetic energy of the drum, and the rest is wasted as heat and sound.
Calculate the efficiency of the motor as a percentage, and calculate the energy wasted as heat and sound each cycle.
Suggest one way the amount of wasted energy could be reduced.
Question 13 [5 marks]
Cell Biology
A student places identical potato chips into salt solutions of different concentrations to investigate osmosis.
One potato chip has a mass of 5.20 g before the experiment. After 24 hours in a 0.4 mol/dm^3 salt solution, the potato chip has a mass of 4.68 g.
Calculate the percentage change in mass of the potato chip, and state whether this is an increase or a decrease. Give your answer to 1 decimal place.
Question 14 [6 marks]
Energy
A homeowner wants to reduce the rate of unwanted energy transfer by heating from their house in winter.
Explain how cavity wall insulation reduces the rate of energy transfer through the walls of a house, and explain why increasing the thickness of insulation gives a smaller and smaller additional benefit as more is added.
Question 15 [6 marks]
Bonding, Structure and the Properties of Matter
Sodium chloride is an ionic compound with a giant ionic lattice structure.
Explain why solid sodium chloride does not conduct electricity, but molten sodium chloride and an aqueous solution of sodium chloride both conduct electricity.
Model solutions
| Question 1[4 marks] | |
|---|---|
| Answer or working | Marks |
| multiplying each isotope's mass by its percentage abundance | M1 |
| (35 x 75) + (37 x 25) | M1 |
| dividing the total by 100 | M1 |
| 35.5 | A1 |
| Question 2[4 marks] | |
|---|---|
| Answer or working | Marks |
| using GPE = m g h | M1 |
| substituting 250 x 9.8 x 12 | M1 |
| correct evaluation | M1 |
| 29400 J (29.4 kJ) | A1 |
| Question 3[4 marks] | |
|---|---|
| Answer or working | Marks |
| using magnification = image size / actual size | M1 |
| substituting 20 / 0.05 | M1 |
| magnification = 400 | A1 |
| stating magnification has no unit, written as x400 | B1 |
| Final answer: x400 magnification | |
| Question 4[5 marks] | |
|---|---|
| Answer or working | Marks |
| using total mass = number of units x mass per unit | M1 |
| substituting 500 x 28 | M1 |
| 14000 | A1 |
| explaining that different polymer chains in the same sample have different lengths (numbers of monomer units) | B1 |
| stating this means the sample contains molecules of different relative molecular mass, so an average value is used to describe the whole sample | B1 |
| Final answer: 14000; different chains in a polymer sample have different lengths, so an average relative molecular mass is used to describe the whole sample | |
| Question 5[5 marks] | |
|---|---|
| Answer or working | Marks |
| total resistance = 15 + 25 = 40 ohms | M1 |
| using I = V / R, substituting 20 / 40 | M1 |
| 0.5 A | A1 |
| using V = I R for the 15 ohm resistor, substituting 0.5 x 15 | M1 |
| 7.5 V | A1 |
| Final answer: 0.5 A current; 7.5 V across the 15 ohm resistor | |
| Question 6[5 marks] | |
|---|---|
| Answer or working | Marks |
| iodine consisting of simple molecules held together by weak intermolecular forces | B1 |
| only weak intermolecular forces needing to be overcome to melt iodine, needing little energy | B1 |
| the covalent bonds within each iodine molecule remaining intact on melting | B1 |
| silicon dioxide having a giant covalent structure with strong covalent bonds throughout | B1 |
| melting silicon dioxide requiring many strong covalent bonds to break, needing much more energy | B1 |
| Final answer: Iodine only needs weak intermolecular forces broken; silicon dioxide needs strong covalent bonds broken | |
| Question 7[6 marks] | |
|---|---|
| Answer or working | Marks |
| converting 4 minutes to seconds, 4 x 60 | M1 |
| energy = power x time, 1500 x 240 | M1 |
| 360000 J | A1 |
| rearranging E = m c (change in temperature) to change in temperature = E / (m c) | M1 |
| substituting 360000 / (2.0 x 4200) | M1 |
| a temperature rise of 42.9 degrees C (3 sf) | A1 |
| Final answer: 360000 J transferred; a temperature rise of about 42.9 degrees C | |
| Question 8[6 marks] | |
|---|---|
| Answer or working | Marks |
| finding the number of electrons in the ion, 2 + 8 = 10 | M1 |
| recognising a 2+ ion has 2 fewer electrons than protons | M1 |
| atomic number = 10 + 2 | M1 |
| atomic number 12 | A1 |
| identifying the element as magnesium | B1 |
| stating the element is in Group 2 (it loses its 2 outer electrons to form a stable ion) | B1 |
| Final answer: Atomic number 12; magnesium; Group 2 | |
| Question 9[6 marks] | |
|---|---|
| Answer or working | Marks |
| recognising the final mass is 108% of the original mass | M1 |
| original mass = final mass / 1.08 | M1 |
| substituting 5.94 / 1.08 | M1 |
| 5.5 g | A1 |
| stating distilled water has a higher water potential than the contents of the potato cells | B1 |
| stating water moved into the cells by osmosis, down the water potential gradient, increasing the mass | B1 |
| Final answer: Original mass 5.5 g; water moved in by osmosis because distilled water has a higher water potential than the cell contents | |
| Question 10[6 marks] | |
|---|---|
| Answer or working | Marks |
| finding the temperature change, 95 - 20 = 75 degrees C | M1 |
| rearranging to c = E / (m x change in temperature) | M1 |
| substituting 87750 / (1.5 x 75) | M1 |
| evaluating 1.5 x 75 = 112.5 | M1 |
| 780 J/kg degrees C | A1 |
| stating this value could be used to identify the metal, by comparing it to known specific heat capacities | B1 |
| Question 11[6 marks] | |
|---|---|
| Answer or working | Marks |
| halogen atoms having more electron shells further down the group | B1 |
| the outer shell being further from the nucleus (a larger atomic radius) | B1 |
| there being increased shielding by inner electron shells | B1 |
| there being a weaker force of attraction between the nucleus and an incoming electron | B1 |
| it being harder for the atom to attract (gain) an extra electron into its outer shell | B1 |
| stating the atom is less reactive further down the group | B1 |
| Final answer: Larger atoms with more shielding attract an extra electron less strongly, so reactivity decreases down Group 7 | |
| Question 12[6 marks] | |
|---|---|
| Answer or working | Marks |
| using efficiency = useful output energy / total input energy | M1 |
| substituting 1050 / 1500 | M1 |
| 0.7 (70%) | A1 |
| wasted energy = total input - useful output | M1 |
| 450 J | A1 |
| a valid way to reduce wasted energy, e.g. lubricating moving parts to reduce friction | B1 |
| Final answer: 70% efficient; 450 J wasted; e.g. lubrication reduces friction and wasted energy | |
| Question 13[5 marks] | |
|---|---|
| Answer or working | Marks |
| finding the change in mass, 4.68 - 5.20 = -0.52 g | M1 |
| dividing the change in mass by the original mass | M1 |
| multiplying by 100 | M1 |
| -10.0% | A1 |
| stating this is a decrease (loss of mass) | B1 |
| Final answer: -10.0% (a decrease in mass) | |
| Question 14[6 marks] | |
|---|---|
| Answer or working | Marks |
| cavity wall insulation containing trapped pockets of air (or foam) within the material | B1 |
| trapped air being a poor conductor of heat, reducing energy transfer by conduction through the wall | B1 |
| trapped pockets of air also reducing energy transfer by convection, by preventing convection currents forming within the cavity | B1 |
| stating the rate of energy transfer through a wall depends on the thickness of the insulating layer | B1 |
| stating doubling the thickness of insulation approximately halves the rate of energy transfer (up to a point) | B1 |
| stating each additional layer of insulation therefore saves progressively less energy than the layer before it, giving diminishing returns | B1 |
| Final answer: Cavity wall insulation traps air, which is a poor conductor and prevents convection, reducing heat loss; but each extra layer reduces the rate of loss by a smaller amount than the last, giving diminishing returns | |
| Question 15[6 marks] | |
|---|---|
| Answer or working | Marks |
| solid sodium chloride having ions held in fixed positions in a rigid lattice | B1 |
| stating the ions cannot move to carry an electric charge in the solid | B1 |
| stating solid sodium chloride therefore does not conduct electricity | B1 |
| the rigid lattice breaking down when the compound is molten, so the ions are free to move | B1 |
| the ions separating and also being free to move when the compound is dissolved in water | B1 |
| stating these free-moving, charged ions can carry an electric current, so molten or dissolved sodium chloride conducts electricity | B1 |
| Final answer: Ions are fixed in place in solid NaCl so cannot carry charge; when molten or dissolved the ions are free to move and can carry an electric current | |