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13+ · Chemistry

CE.S-C3 Chemistry: The Periodic Table and Separating Mixtures

ISEB CE ISEB CE 13+ Science (Chemistry) · Calculator allowed · about 70 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

All substances can be classified as elements, compounds or mixtures.

(a)State what is meant by the term 'element'.(1)

(b)State what is meant by the term 'compound'.(1)

(c)State one way in which a mixture is different from a compound.(1)

(Total for Question 1 is 3 marks)

The table below lists six substances.
A: oxygen gas, O2
B: water, H2O
C: air (a blend of gases including nitrogen, oxygen, carbon dioxide and argon)
D: sea water (water with several different salts dissolved in it)
E: iron, Fe
F: bronze (a solid made by mixing/melting together copper and tin)

(a)State whether substance A (oxygen gas, O2) is an element, a compound or a mixture.(1)

(b)State whether substance B (water, H2O) is an element, a compound or a mixture.(1)

(c)State whether substance C (air) is an element, a compound or a mixture.(1)

(d)State whether substance D (sea water) is an element, a compound or a mixture.(1)

(e)State whether substance E (iron, Fe) is an element, a compound or a mixture.(1)

(f)State whether substance F (bronze) is an element, a compound or a mixture.(1)

(Total for Question 2 is 6 marks)

Give the correct chemical symbol for each of the following elements.

(a)Sodium(1)

(b)Potassium(1)

(c)Iron(1)

(d)Oxygen(1)

(Total for Question 3 is 4 marks)

Elements can be classified as metals or non-metals based on their physical properties.

(a)State two physical properties typical of metals.(2)

(b)State two physical properties typical of non-metals.(2)

(Total for Question 4 is 4 marks)

Substances can exist as a solid, a liquid or a gas. This depends on the arrangement and movement of their particles.

(a)Describe the arrangement and movement of particles in a solid.(2)

(b)Describe the arrangement and movement of particles in a liquid.(2)

(c)Describe the arrangement and movement of particles in a gas.(2)

(Total for Question 5 is 6 marks)

Name the change of state described in each case below.

(a)A solid turning into a liquid.(1)

(b)A liquid turning into a solid.(1)

(c)A liquid turning into a gas.(1)

(d)A gas turning into a liquid.(1)

(Total for Question 6 is 4 marks)

Chidi wants to separate a mixture of sand and water using filtration.

(a)Name the piece of apparatus used to hold the filter paper during filtration.(1)

(b)Describe how filtration separates the sand from the water.(2)

(c)State the name given to the sand that remains on the filter paper, and the name given to the liquid that passes through.(2)

(Total for Question 7 is 5 marks)

Amara has a solution of salt dissolved in water and wants to obtain dry salt crystals from it.

(a)Describe how Amara could use evaporation to obtain dry salt crystals from the solution.(2)

(b)Explain why Amara should not heat the solution very strongly right until the very end of the process.(2)

(Total for Question 8 is 4 marks)

Simple distillation can be used to obtain pure water from salt water.

(a)Explain how distillation separates pure water from a salt solution.(3)

(b)State the piece of apparatus used to cool and condense the water vapour.(1)

(Total for Question 9 is 4 marks)

The diagram shows the apparatus used to separate pure water from salt water by simple distillation. Label 1 shows a round flask, heated from below, containing the boiling salt solution. Label 2 shows a thermometer, with its bulb positioned level with the side arm of the flask. Label 3 shows a long, sloped glass tube surrounded by an outer water jacket, connected to the side arm. The apparatus ends with a beaker collecting the liquid that drips out.

Figure (to be drawn): Simple distillation set-up: 1 = round-bottomed flask containing salt solution, heated on a tripod and gauze over a Bunsen burner; 2 = thermometer inserted through a bung, its bulb level with the side arm; 3 = a sloped condenser tube surrounded by an outer water jacket, connected to the side arm, with water entering the jacket at the lower end and leaving at the upper end; the condenser leads down into a beaker collecting the distillate.

(a)Name the piece of apparatus labelled 1, which holds the boiling solution and is heated directly.(1)

(b)Name the piece of apparatus labelled 2, used to monitor the temperature of the vapour leaving the flask.(1)

(c)Name the piece of apparatus labelled 3, in which the vapour is cooled and turns back into a liquid.(1)

(d)State the direction water flows through the outer jacket of the condenser (enters at the top or bottom), and explain why it flows this way.(1)

(Total for Question 10 is 4 marks)

A mixture of food dyes is separated using paper chromatography.

(a)Describe how you would set up an experiment to separate the dyes in a mixture of food colourings using paper chromatography. Refer to the paper and the solvent in your answer.(2)

(b)A single dye in the mixture travels 6.0 cm from the baseline while the solvent front travels 8.0 cm. Calculate the Rf value of this dye.(2)

(c)State why paper chromatography can be used to identify an unknown dye.(2)

(Total for Question 11 is 6 marks)

Rock salt is a mixture of salt and insoluble sand. Priya wants to obtain a sample of pure, dry salt from a sample of rock salt.

(a)Priya first dissolves the rock salt in water. Name the process she should use next to remove the insoluble sand from the mixture.(1)

(b)Name the process Priya should use next to obtain dry salt crystals from the remaining salt solution.(1)

(c)Explain why Priya must dissolve the rock salt in water and filter it before she can evaporate the solution, rather than heating the solid rock salt mixture directly.(2)

(d)State one property of sand that means it cannot be separated from a salt solution by evaporation alone.(1)

(Total for Question 12 is 5 marks)

A pupil investigates how temperature affects the rate at which water evaporates from an open dish. She sets up four identical dishes, each containing 50 cm³ of water, and places them in rooms kept at 15C, 20C, 25C and 30C. She measures the volume of water remaining in each dish after 24 hours.

(a)State the independent variable in this investigation.(1)

(b)State the dependent variable in this investigation.(1)

(c)State one variable that should be controlled (kept the same) in this investigation.(1)

(d)Suggest one reason why the pupil used the same size and shape of dish for each temperature.(1)

(e)Suggest one improvement the pupil could make to increase the reliability of her results.(1)

(Total for Question 13 is 5 marks)

The table shows the melting point and boiling point of four substances, P, Q, R and S, all measured at normal atmospheric pressure.
P: melting point -218C, boiling point -183C
Q: melting point 0C, boiling point 100C
R: melting point 801C, boiling point 1413C
S: does not melt sharply at one temperature; begins to soften at about 300C and is completely melted by about 340C

(a)State the physical state of substance P at 25C (room temperature). Explain your answer.(2)

(b)State the physical state of substance R at 25C.(1)

(c)Substance Q has the formula H2O and substance R has the formula NaCl. State whether Q and R are elements or compounds, and explain how you know from their formulae.(2)

(d)Unlike P, Q and R, substance S does not melt sharply at one fixed temperature. Suggest, giving a reason, whether S is more likely to be a pure substance or a mixture.(1)

(Total for Question 14 is 6 marks)

A student runs paper chromatography to identify an unknown food dye, X, found in a sports drink. She runs three known reference dyes, A, B and C, on the same paper alongside dye X, using the same solvent. The solvent front travels 10.0 cm. The table shows the distance travelled by each dye spot.
Dye A: 7.5 cm
Dye B: 4.0 cm
Dye C: 6.0 cm
Dye X: 6.0 cm

(a)Calculate the Rf value of dye A.(2)

(b)Calculate the Rf value of dye X.(2)

(c)Using your results, identify which known dye (A, B or C) is most likely to be the same substance as dye X, and justify your answer.(2)

(Total for Question 15 is 6 marks)

The table shows the melting point and how vigorously each Group 1 (alkali) metal reacts with cold water.
Lithium: melting point 181C; reacts fairly gently, a steady stream of bubbles
Sodium: melting point 98C; reacts vigorously, fizzes rapidly and melts into a ball
Potassium: melting point 63C; reacts very vigorously, bursts into a lilac flame

(a)Describe the trend in melting point as you go down Group 1 from lithium to potassium.(1)

(b)Describe the trend in reactivity with water as you go down Group 1.(1)

(c)Rubidium (Rb) is the next element down Group 1, below potassium. Predict, giving a reason, the melting point of rubidium compared with potassium's 63C.(2)

(d)Predict how rubidium would react with cold water, compared with potassium.(1)

(Total for Question 16 is 5 marks)

Pure water freezes and melts at exactly 0C, but salt water (a mixture of salt and water) freezes over a range of temperatures below 0C.

(a)State the general term used for a substance, like salt water, that does not have one exact melting or boiling point.(1)

(b)Explain, in terms of particles, why dissolving salt in water lowers the temperature at which the mixture freezes, compared with pure water.(2)

(c)State one everyday use of this effect (that salt water freezes at a lower temperature than pure water).(1)

(Total for Question 17 is 4 marks)

A mixture contains iron filings, salt and sand, all mixed together as dry solids. Describe, in detail, a sequence of steps that could be used to separate this mixture into three pure, dry substances: iron filings, sand and salt. In your answer, refer to the physical property of each substance that allows it to be separated at each stage.

(Total for Question 18 is 6 marks)

A student is given an unknown solid substance, X, and makes the following observations: it melts sharply at 660C and boils at 2470C; it conducts electricity well both as a solid and as a liquid; it is shiny, and can be hammered into thin sheets without shattering.

(a)State, giving a reason, whether X is more likely to be a pure substance (element or compound) or a mixture.(2)

(b)State, giving two reasons from the observations, whether X is more likely to be a metal or a non-metal.(2)

(c)Suggest which method, filtration or evaporation, could be used to recover solid X if it were dissolved in water, and explain your answer.(1)

(Total for Question 19 is 5 marks)

If a bottle of perfume is opened at one side of a room, its scent can be smelled at the other side of the room after a short time, even without any air currents blowing directly across the room.

(a)Explain, in terms of particles, how the smell of the perfume reaches the other side of the room.(2)

(b)Explain why the scent would spread across the room more quickly on a warm day than on a cold day.(2)

(Total for Question 20 is 4 marks)

Mark scheme · CE.S-C3 Chemistry: The Periodic Table and Separating Mixtures

Question 1

(a) B1 a substance made of only one type of atom, which cannot be broken down into anything simpler by chemical means, oe
(a) Answer: A substance made of only one type of atom.
(b) B1 two or more elements chemically combined together in fixed proportions, oe
(b) Answer: Two or more elements chemically combined together in fixed proportions.
(c) B1 in a mixture the substances are not chemically combined/joined (they can be present in any proportion and can be separated by physical methods), oe
(c) Answer: In a mixture the substances are not chemically combined, so they can be present in any proportion and separated by physical means.

Question 2

(a) B1 element, cao
(a) Answer: Element
(b) B1 compound, cao
(b) Answer: Compound
(c) B1 mixture, cao
(c) Answer: Mixture
(d) B1 mixture, cao
(d) Answer: Mixture
(e) B1 element, cao
(e) Answer: Element
(f) B1 mixture, cao
(f) Answer: Mixture

Question 3

(a) B1 Na, cao
(a) Answer: Na
(b) B1 K, cao
(b) Answer: K
(c) B1 Fe, cao
(c) Answer: Fe
(d) B1 O, cao
(d) Answer: O

Question 4

(a) B1 any one of: shiny/lustrous, good conductor of heat and electricity, malleable/ductile, high melting and boiling point, sonorous (makes a ringing sound), high density
(a) B1 a second, different valid property from the list above
(a) Answer: Any two of: shiny; good conductor of heat and electricity; malleable/ductile; high melting point; sonorous; high density.
(b) B1 any one of: dull appearance, poor conductor of heat and electricity (insulator), brittle when solid, low melting and boiling point, low density
(b) B1 a second, different valid property from the list above
(b) Answer: Any two of: dull appearance; poor conductor of heat and electricity; brittle when solid; low melting point; low density.

Question 5

(a) B1 particles are closely packed together in a regular, fixed arrangement, oe
(a) B1 particles vibrate about fixed positions and do not move from place to place, oe
(a) Answer: Particles are closely packed in a regular, fixed arrangement, and only vibrate about fixed positions.
(b) B1 particles are close together but randomly arranged, oe
(b) B1 particles can move/slide past each other, oe
(b) Answer: Particles are close together but randomly arranged, and can move/slide past each other.
(c) B1 particles are far apart, randomly arranged, oe
(c) B1 particles move quickly, randomly, in all directions, oe
(c) Answer: Particles are far apart and randomly arranged, and move quickly and randomly in all directions.

Question 6

(a) B1 melting, cao
(a) Answer: Melting
(b) B1 freezing, cao
(b) Answer: Freezing
(c) B1 evaporating/boiling, cao
(c) Answer: Evaporating (boiling)
(d) B1 condensing, cao
(d) Answer: Condensing

Question 7

(a) B1 filter funnel, cao
(a) Answer: Filter funnel
(b) B1 the filter paper has very small holes/pores that let the water particles pass through, oe
(b) B1 but the (insoluble) sand particles are too large to pass through, so they are trapped/left behind on the paper, oe
(b) Answer: The filter paper's tiny pores let water pass through but are too small for the insoluble sand particles, which are trapped on the paper.
(c) B1 residue (for the sand), cao
(c) B1 filtrate (for the liquid), cao
(c) Answer: Sand = residue; water = filtrate.

Question 8

(a) B1 heat the solution gently, e.g. in an evaporating basin over a Bunsen burner, oe
(a) B1 so the water (solvent) evaporates away, leaving the dissolved salt behind as dry solid crystals, oe
(a) Answer: Heat the solution gently (e.g. in an evaporating basin) so the water evaporates away, leaving dry salt crystals behind.
(b) B1 heating too strongly/quickly near the end can cause the salt to spit/spurt out of the container (or decompose), oe
(b) B1 so heating should be slowed/stopped once most of the water has gone, leaving a hot saturated solution to cool and crystallise (or to evaporate the rest more gently), oe
(b) Answer: Strong heating near the end can make the salt spit out of the container, so heating should be slowed once a hot saturated solution remains, allowing it to cool and crystallise gently.

Question 9

(a) B1 the solution is heated so that the water (solvent) boils and evaporates, leaving the dissolved salt behind in the flask, oe
(a) B1 the water vapour passes into a condenser, where it is cooled, oe
(a) B1 the vapour condenses back into a liquid (pure water/the distillate), which is collected, while the salt stays behind in the flask, oe
(a) Answer: The solution is boiled; the water evaporates and passes into a condenser where it cools and condenses back into pure liquid water, which is collected, while the salt remains behind in the flask.
(b) B1 condenser, cao
(b) Answer: Condenser

Question 10

(a) B1 (round-bottomed) flask, cao
(a) Answer: Flask
(b) B1 thermometer, cao
(b) Answer: Thermometer
(c) B1 condenser, cao
(c) Answer: Condenser
(d) B1 water enters at the bottom (nearest the flask) and leaves at the top, so that the condenser is always kept completely full of water, giving the maximum possible cooling along its whole length, oe
(d) Answer: Water enters at the bottom and leaves at the top, keeping the condenser completely full of water for maximum cooling.

Question 11

(a) B1 a small spot of the dye mixture is placed near the bottom of a strip of chromatography paper, above the level where the solvent will sit, oe
(a) B1 the paper is placed upright in a shallow layer of solvent in a beaker/container, and the solvent moves up the paper, carrying the different dyes with it at different rates, oe
(a) Answer: A spot of the dye mixture is placed near the bottom of chromatography paper, which stands in a shallow layer of solvent; the solvent moves up the paper, carrying the dyes at different rates.
(b) M1 Rf = distance moved by dye / distance moved by solvent = 6.0 / 8.0
(b) A1 0.75, cao
(b) Answer: 0.75
(c) B1 each different substance/dye has its own characteristic Rf value in a given solvent, oe
(c) B1 so the Rf value of an unknown spot can be compared with the Rf values of known dyes run on the same paper/in the same solvent, to identify it, oe
(c) Answer: Each dye has a characteristic Rf value in a given solvent, so an unknown dye's Rf can be compared to known dyes run under the same conditions to identify it.

Question 12

(a) B1 filtration, cao
(a) Answer: Filtration
(b) B1 evaporation (crystallisation), cao
(b) Answer: Evaporation
(c) B1 the sand is insoluble in water, so dissolving the mixture and filtering it removes the sand while the soluble salt passes through in solution, oe
(c) B1 only once the sand has been removed can the remaining salt solution be evaporated to leave pure, dry salt crystals with no sand mixed in, oe
(c) Answer: Dissolving and filtering removes the insoluble sand first, so the remaining solution can then be evaporated to give pure salt with no sand mixed in.
(d) B1 sand does not dissolve in water (it is insoluble), so evaporating the water would leave it mixed in with the salt crystals rather than removing it, oe
(d) Answer: Sand is insoluble, so evaporation alone would leave it mixed in with the salt rather than removing it.

Question 13

(a) B1 temperature (of the room), cao
(a) Answer: Temperature
(b) B1 volume of water remaining after 24 hours (or rate of evaporation), cao
(b) Answer: Volume of water remaining after 24 hours
(c) B1 any one of: starting volume of water, size/shape of dish (surface area), time left (24 hours), amount of air movement/humidity, oe
(c) Answer: For example, the starting volume of water (50 cm³) in each dish.
(d) B1 so that each dish has the same surface area of water exposed to the air, making it a fair test (otherwise a larger surface area would evaporate water faster regardless of temperature), oe
(d) Answer: So each dish has the same surface area of water exposed to the air, keeping the test fair.
(e) B1 repeat the experiment (at each temperature) and calculate a mean result, oe
(e) Answer: Repeat the experiment at each temperature and calculate a mean.

Question 14

(a) B1 gas, cao
(a) B1 because room temperature (25C) is above its boiling point (-183C), oe
(a) Answer: Gas, because room temperature (25C) is well above its boiling point of -183C.
(b) B1 solid, because room temperature (25C) is below its melting point of 801C, oe
(b) Answer: Solid
(c) B1 both are compounds, cao
(c) B1 because each formula contains two different elements chemically combined (H and O in Q; Na and Cl in R), oe
(c) Answer: Both are compounds, because each formula shows two different elements chemically combined together.
(d) B1 a mixture, because pure substances melt at one sharp, fixed temperature, whereas mixtures melt/soften over a range of temperatures, oe
(d) Answer: A mixture, because it softens over a range of temperatures rather than melting sharply at one fixed point.

Question 15

(a) M1 Rf = 7.5 / 10.0
(a) A1 0.75, cao
(a) Answer: 0.75
(b) M1 Rf = 6.0 / 10.0
(b) A1 0.6, cao
(b) Answer: 0.6
(c) B1 dye C, cao
(c) B1 because dye C has the same distance travelled (6.0 cm), giving the same Rf value (0.6) as dye X under the same conditions (same solvent and paper), oe
(c) Answer: Dye C, because it has the same Rf value (0.6) as dye X.

Question 16

(a) B1 melting point decreases going down the group, oe
(a) Answer: Melting point decreases down the group.
(b) B1 reactivity increases going down the group, oe
(b) Answer: Reactivity increases down the group.
(c) B1 lower than 63C (any sensible value below 63C, e.g. around 30-45C)
(c) B1 because melting point continues to decrease going down the group, following the pattern shown by lithium, sodium and potassium, oe
(c) Answer: Lower than 63C (the real value is about 39C), because melting point continues to decrease down the group.
(d) B1 even more vigorously than potassium, oe
(d) Answer: Even more vigorously than potassium.

Question 17

(a) B1 mixture (impure substance), cao
(a) Answer: Mixture
(b) B1 the dissolved salt particles get in the way of/disrupt the water particles arranging themselves into the regular pattern of ice, oe
(b) B1 so a lower temperature is needed before the water particles have little enough energy to form the solid structure, meaning the mixture freezes below 0C, oe
(b) Answer: Dissolved salt particles disrupt the water particles forming the regular ice structure, so a lower temperature is needed before freezing occurs.
(c) B1 salt is spread on icy roads/pavements in winter to lower the freezing point of water and prevent ice forming/help melt existing ice, oe
(c) Answer: Salt is spread on icy roads or pavements in winter to lower the freezing point and help prevent or melt ice.

Question 18

Level 1 (1-2): Basic, isolated statement(s) naming one or two separation techniques, with little or no reference to the properties that make them work, and/or an incomplete or muddled sequence.
Level 2 (3-4): Most of the separation techniques needed (magnetic separation, dissolving and filtration, evaporation) are identified in a broadly sensible order, with some reference to the relevant properties of the substances, though the explanation may be incomplete in places.
Level 3 (5-6): A complete, logically ordered sequence of steps that separates all three substances as pure, dry solids, with each step clearly linked to the specific physical property (magnetism, solubility, and the fact that water can be evaporated away) that makes it work, using accurate scientific vocabulary throughout.
Indicative content:
- Iron filings are magnetic, so a magnet is passed through/over the dry mixture first to attract and remove the iron filings, leaving salt and sand mixed together.
- The remaining salt and sand mixture is added to water and stirred; the salt dissolves (is soluble) but the sand does not (is insoluble).
- The mixture is then filtered: the insoluble sand is left behind on the filter paper as the residue, while the salt solution passes through as the filtrate.
- The sand residue is washed and left to dry (e.g. in a warm place or oven) to give pure, dry sand.
- The filtrate (salt solution) is then heated/evaporated (e.g. in an evaporating basin) so the water evaporates off, leaving pure, dry salt crystals behind.
- Overall order: magnetic separation removes the iron filings first; dissolving and filtration then separate the sand from the salt (in solution); evaporation of the filtrate finally gives the salt.

Question 19

(a) B1 a pure substance (element or compound), cao
(a) B1 because it has one sharp, fixed melting point and boiling point, which is characteristic of a pure substance rather than a mixture (which melts/boils over a range), oe
(a) Answer: A pure substance, because it has one sharp, fixed melting and boiling point.
(b) B1 a metal, cao
(b) B1 because it conducts electricity well and is shiny and malleable (can be hammered into sheets without shattering), any two of these properties cited, oe
(b) Answer: A metal, because it conducts electricity well and is shiny and malleable.
(c) B1 evaporation, because X would be dissolved in solution (not an insoluble solid mixed with the water), so filtration would not separate it out; only evaporating the water would leave X behind, oe
(c) Answer: Evaporation, because X would be dissolved in solution, so filtration could not remove it; only evaporating the water leaves X behind.

Question 20

(a) B1 perfume particles evaporate from the liquid to form a gas, oe
(a) B1 gas particles move quickly and randomly in all directions, spreading out (diffusing) from a region of higher concentration near the bottle to a region of lower concentration across the room, until detected, oe
(a) Answer: Perfume particles evaporate into a gas and move quickly and randomly in all directions, diffusing from high to low concentration until they spread across the room.
(b) B1 on a warm day the particles have more (kinetic) energy, oe
(b) B1 so more perfume evaporates and/or the gas particles move faster, meaning diffusion happens more quickly across the room, oe
(b) Answer: On a warm day particles have more kinetic energy, so more perfume evaporates and the gas particles move faster, making diffusion quicker.

Chemistry: The Periodic Table and Separating Mixtures - Worksheets, Questions and Revision