Observations and Measurements

Use Fig. 3.1 to complete this table:

The abnormal cells are very rigid and cannot easily bend. This, and their different shape, can lead to problems in the circulation of blood in a person suffering from sickle cell anaemia. Suggest why.

______

Record your observations in the table.

Use pH indicator paper to find the pH of the milk, yoghurt-milk mixture and live yoghurt.
Record your results in the table above.

State how you could determine when the milk reaches a temperature of $85\,^\circ\text{C}$.

______

After the milk has been cooled to a temperature of $45\,^\circ\text{C}$, a small volume of live yoghurt is added to it. This mixture is stirred and left at $45\,^\circ\text{C}$ for 8 hours. After this time, the milk has turned to yoghurt which can be cooled and eaten.

Using information in the table on page 2, suggest two ways you could check that the milk has been turned into yoghurt.

1. ______
2. ______

In Table 1.1, record your observations of the crushed apple at 0 minutes.

Start timing.

Record the start time. ______

Observe the colour of the crushed apple in each test-tube at 5, 10 and 15 minutes and record your observations in Table 1.1.

Table 1.1

Use the universal indicator paper that has been provided to test and record the pH of the distilled water and the pH of the vitamin C solution.

distilled water pH ______
vitamin C solution pH ______

Draw a straight line on the photograph to join A and B.

Measure and record the length of this line.

length of line A–B = ______ $\text{mm}$

On your drawing, draw a line at the same location as the line A–B.

Measure and record the length of this line.

length of line on drawing = ______

Fig. 2.2 is a photograph of a leaf from a sweet potato plant.

Describe one visible difference and one visible similarity in the structure of the potato leaf in Fig. 2.1 and the sweet potato leaf in Fig. 2.2.

difference = ______
similarity = ______

After 10 minutes remove the test-tubes from the water bath and place them in the test-tube rack.

Record the time ______

Observe the appearance of the contents of each test-tube and record your observations in Table 1.1.

Table 1.1

Leave the test-tubes in the rack for a further twenty minutes.

While you are waiting continue with the other questions.

Describe any differences in appearance of the contents of the test-tubes containing glucose solution, after they have been left in the rack for twenty minutes.

______

Solids are often formed after the Benedict’s test. Suggest how you could separate any solid produced after the test and obtain its mass.

______

Complete Table 2.1 by describing differences that can be seen between the named features of the blood cells in these two samples.

Table 2.1

Explain how, using features visible in Fig. 2.1 and Fig. 2.2, blood is adapted for transporting oxygen around the body.

______

Suggest why two strips were used, rather than one, in each solution.

______

Complete Table 1.1.

Table 1.1

Using the information in Table 1.1 draw a graph, on the axes provided, of mean change in length against concentration of solution.

Describe the observable differences between one piece of S1 and one piece of S2.

______

• Using forceps, dip the cut surface of one piece of S1 and one piece of S2 into the iodine solution for approximately 3 seconds.

Describe and explain the observable differences between S1 and S2 after this test.

______

• Cut the other pieces of S1 and S2 each into three equal parts.
• Test one of these pieces of S1 and one of these pieces of S2 for reducing sugar.

Complete the table below by recording your observations and conclusions.

Complete the table below by describing the appearance of the two pieces of S1 and S2.