You are required to investigate the effect of concentration of hydrochloric acid (independent variable) on the rate of diffusion. The investigation involves placing agar cubes containing an indicator into dilute hydrochloric acid. As the acid diffuses into the agar cubes the indicator changes colour. You are provided with the materials shown in Table 1.1. Table 1.1 labelled, contents, hazard, volume/cm³ H, 1.0mol dm⁻³ hydrochloric acid, irritant, 100 A, agar, none, – W, distilled water, none, 60 It is recommended that you wear suitable eye protection. If H comes into contact with your skin, wash it off immediately under cold water. You must not touch the agar with your hands. Use the blunt forceps and paper towel to handle the agar. You will need to carry out a trial test (step 1 to step 4) before you start your investigation. Read step 1 to step 4 before proceeding. 1. Cut 3 cubes from the agar, A, as shown in Fig. 1.1. Each cube should be approximately 5mm x 5mm x 5mm but they must all have the same dimensions. Cut the cubes from A on the white tile provided. [Figure 1.1] 2. Put 10 cm³ of 1.0moldm⁻³ hydrochloric acid, H, into a beaker. 3. Put the 3 cubes you cut in step 1 into the beaker containing H, using blunt forceps. Start timing. As the acid diffuses into the agar cubes they change colour. The end-point is reached when the blue-green colour disappears and the whole cube has changed colour from blue-green to pink. Putting the beaker on the white card provided may help you to see the colour changes more clearly. 4. Measure the time taken for each cube to reach the end-point and record the times in (a)(i). If any cube remains blue-green after 3 minutes record as 'more than 180'.