10 Coordinated ScienceMock Examination

CANDIDATE NAMETEACHER NAME

_______________________________________________Paper 6 Alternative to Practical 0654/61

July/August 20141 hour

Candidates answer on the Question paperNo additional materials are required

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READ THESE INSTRUCTIONS FIRSTWrite your name on all the work you hand in. Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs, tables or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.Answer all questions.The number of marks is given in brackets [ ] at the end of each question or part question.

For Examiner’s UseQuestion 1 /3Question 2 /5Question 3 /10Question 4 /10Question 5 /12Question 6 /10Question 7 /10Total /60Percentage %

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1. Kalpana wants to use a measuring cylinder to find a volume of water.

She has three measuring cylinders to choose from.

(i) Which measuring cylinder would give the most precise measurement? Explain your answer. [2]

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(ii) The most precise measuring cylinder may not give an accurate reading. Suggest why. [1]

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2. A student had read about a glacier that had been covered in insulating material. The idea was to slow down the rate at which the glacier melts in the summer.

She investigated this idea using the apparatus shown in the diagram.

(a) These are the steps taken by the student:

Measure 30 cm3 of cold water into a boiling tube. Place the boiling tube 25 cm from an infra red lamp. Record the temperature of the water. Switch on the infra red lamp. Record the temperature of the water every minute for 5 minutes. Repeat with boiling tubes covered in different insulating materials.

(i) Why did she use an infra red lamp?

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(ii) Name one control variable in this investigation.

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(iii) Give one advantage of using a temperature sensor and data logger instead of a glass thermometer to measure temperature.

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(b) The results of the investigation are shown in the graph.

(i) Why did the student use a boiling tube with no insulation?

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(ii) From her results, what should she recommend is used to insulate the glacier?

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[Total 5 marks]

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3. A student did an experiment with two digestive enzymes, amylase and pepsin, to find whether pH affects their activity. Pepsin breaks down protein in the stomach. Amylase breaks down starch in the mouth and small intestine.

Pepsin TestWhen the enzyme is added to a cloudy protein suspension it will become clear if the protein is digested.

The student prepared three test-tubes as shown in Fig. 3.1.

Fig 3.1 Water was added where necessary to make all three tubes have the same total volume of liquid.

Amylase TestThis enzyme is added to a starch solution. If the starch is digested, iodine remains light brown when tested with the reaction mixture.The student prepared three more test tubes as shown in Fig. 3.2.

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Water was added where necessary to make all three tubes have the same total volume of liquid.

The student put all six test-tubes into a water bath at 40 oC for five minutes. Then she observed the tubes. She studied the appearance of tubes 1, 2 and 3. Then she tested small samples of tubes 4, 5 and 6 with iodine and looked for a colour change.

(a) (i) Complete the second column of Fig 3.3 to show the contents of each tube.

Fig 3.3 [1]

(ii) Digestion of protein occurred only in tube 2. In Fig. 3.3 complete the observations for tubes 1, 2 and 3. [2]

(iii) Digestion of starch occurred only in tube 4. In Fig 3.3 complete the observations for tubes 4, 5 and 6 when they were tested with iodine. [2]

(b)

(i) Which enzyme worked better in conditions of low pH?

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(ii) Explain the observations for tube 5 in terms of enzyme action.

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(iii) Why were tubes 3 and 6 included in the experiment?

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(c) Describe a test to show that amylase and pepsin solutions contain protein.

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4. A farmer's bean crop is poor. He thinks that the soil in his field may be too acidic. He gives a science student three samples, A, B and C of the soil for testing.

There are two parts to the tests.

Part 1

The student takes some of sample A and mixes it with water. He separates the water from the soil by filtering the mixture. This gives soil washing A.

He repeats this procedure to give soil washings B and C.

(a) Suggest one practical detail of this procedure that enables a fair comparison of the three soil samples.

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Part 2

The student wants to find out what volume of soil washing A is needed to

neutralise 10 cm3 of aqueous calcium hydroxide solution. See Fig. 4.1.

Fig 4.1

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He places 10cm3 of calcium hydroxide solution in a beaker and adds a few drops of litmus.

He places 10 cm3 soil washing A in a measuring cylinder. He uses a dropper to add soil washing A from the measuring cylinder, drop

by drop, to the calcium hydroxide in the beaker, until the litmus changes colour.

He notes how much soil washing A is left in the measuring cylinder and records the volume in Table 3.1.

He repeats this procedure with soil washings B and C.

(b) State the colour change of the litmus.

from …………………………………. to ………………………………………[2]

Fig. 4.2 shows the scales of the measuring cylinder containing soil washings A, B and C after the litmus has changed colour.

Fig 4.2(c) (i) Read the volumes left in the measuring cylinders and record them in Table 4.1 (next page). [3]

(ii) Calculate the volumes of soil washings A, B and C added to the calcium hydroxide solution. Record them in Table 4.1. [1]

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Table 4.1

Use data from the third column of Table 2.1 to calculate the average volume, Vav, of the soil washings added. Show your working.

Vav = …………………. cm3

[2]

(d) The concentration of the calcium hydroxide solution is 0.013 mol/dm3.

Using the equation given, calculate the concentration of the acid in the soil washings.

concentration of acid =

(2 × 0.013 × 10)

concentration of acid = ……………………… mol / dm3 [1]

[Total 10 marks]

Vav

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5. A student used apparatus to investigate how breathing was affected by exercise. In this apparatus the experimenter breathes in and out of the apparatus through a tube. The volume of air breathed in and out over time is measured and displayed on an oscilloscope.

The student did the first reading while resting. The oscilloscope trace is shown in Fig. 5.1.

Fig 5.1

(i) What is the volume of air inhaled in one breath?

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(ii) Calculate how many breaths the student took in one minute. Show your working.

breaths in one minute = ……………………… [2]

(iii) Calculate the total volume of air inhaled in one minute. Show your working.

total volume air inhaled in one minute = ……………………… [2]

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(b) The student did some exercise then took some readings using the same apparatus. The oscilloscope trace of his results is shown in Fig. 5.2.

Fig 5.2

(i) Study the two oscilloscope traces. Describe two differences between them.

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(ii) What volume of air was inhaled in the first breath after exercise?

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This question is continued on the next page.

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(iii) Explain why this volume was different from the volume inhaled while resting.

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(c) In the apparatus the exhaled air is not breathed back in again during the experiment. Give two reasons why it would be undesirable to breathe the exhaled air back in.

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[Total 12 marks]

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6. A student is given some plasticine (modelling clay) by his teacher. He is told to find the density of the plasticine by two different methods.

Method 1The student tries to make the plasticine into a cube. He measures the cube so that he can calculate its volume.

Then he weighs the cube of plasticine on a balance.

He calculates the density using the mass and volume.

(a) (i) Fig. 6.1 shows one face of the cube of plasticine. As accurately as you can, measure one side of the face of the cube to the nearest millimetre. Use this measurement to calculate the volume of the cube in cubic centimetres.

Fig 6.1

length of one side of the cube = …………………. mm

length of one side of the cube = …………………. cm

volume of the cube = …………. x ………… x ……..… = …………… cm3 [2]

(ii) The student puts the cube onto a balance. Fig. 6.2 shows the window of the balance. Read and record the mass of the cube.

Fig 6.2

mass of the cube = ……….. g [1]

This question is continued on the next page15

Use the answers to (a)(i) and (ii) to calculate the density of the plasticine in

g/cm3.

density of plasticine = ……….... g / cm3 [1]

Method 2The student finds the volume of the plasticine by the displacement method. Then he weighs it using a metre rule. He calculates the density of plasticine again.

(b) The student puts 100 cm3 of water into a measuring cylinder. Then he places the plasticine into the water. Fig. 6.3 shows the new level of water in the measuring cylinder.

(i) Read the level of water in the measuring cylinder. Then calculate the volume of the plasticine.

Fig. 6.3

water level in the measuring cylinder = ….…………. cm3

volume of the plasticine = …………….. cm3 [1]

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The student hangs a 50 g mass on a metre rule at the 30 cm mark. He hangs the plasticine on the other end so that the rule balances.

(ii) Use Fig. 6.4 to calculate the distances of the plasticine and the 50 g mass from the pivot.

Fig 6.4 The distance d1 of the 50 g mass from the pivot is …………… cm

The distance d2 of the plasticine from the pivot is …………… cm [1]

(iii) Use the following equation to calculate the mass of the plasticine.

d1 x 50 = d2 x mass of the plasticine

mass of the plasticine = ……………… g [1]

(iv) Calculate the density of the plasticine using your answers to (b)(i) and (iii).

density of plasticine = ………………. g / cm3 [1]

(c) Which measurement of volume, (a)(i) or (b)(i), is more accurate? Give a reason for your answer.

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[Total 10 marks]

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7. This question is about magnesium and two of its compounds. Fig. 7.1 shows how the magnesium compounds are formed.

Be careful to use the correct scientific words when you write the answers.

Fig 7.1

(a) A student burns a piece of magnesium ribbon in air.

(i) Explain how he can safely carry out this experiment.

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He adds the white powder he has made to a test-tube half-filled with water. He shakes the tube. The mixture is cloudy.

(ii) What does this tell him about magnesium oxide?

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He adds Universal Indicator to the mixture from (i). The mixture turns blue.

(iii) What does this tell him about the mixture?

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(b) The student half-fills a small beaker with dilute sulfuric acid. He warms the acid. He adds a spatula-full of magnesium oxide to the warm acid and stirs the mixture. The white powder disappears into the clear sulfuric acid.

(i) What does this tell the student about magnesium oxide?

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The student adds more magnesium oxide to the acid. The mixture of acid and magnesium oxide turns cloudy, like the mixture in (a)(i).

(ii) Why does the student add magnesium oxide until the mixture is cloudy?

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(iii) Draw a diagram to show how the student obtains clear aqueous magnesium sulfate from the mixture in the beaker.

[2]

(c) The student places the aqueous magnesium sulfate in a dish on top of a beaker half full of water. He heats the water so that it boils. After a few minutes there is still a liquid in the dish, but no solid has formed.

(i) Why does the student heat the aqueous magnesium sulfate in this way?

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After a while, about 20 cm3 of the aqueous magnesium sulfate is left in the dish. The student stops heating and allows the dish to cool down to room temperature. Crystals of magnesium sulfate begin to form.

(ii) Explain why the crystals now begin to form.

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End of Examination

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