0:00:00.000,0:00:06.006 Experiment - OB11. To compare the levels of Carbon Dioxide in Inhaled & Exhaled Air. 0:00:06.022,0:00:12.622 Safety googles and gloves must always be worn, when chemicals are involved. 0:00:12.622,0:00:20.572 We have 2 testubes containing limewater. Limewater is a clear solution and it turns milky when Carbon 0:00:20.572,0:00:24.527 Dioxide is present... 0:00:24.527,0:00:27.612 The testube on the left, contains a stopper which has 2 pieces of tubing. 0:00:27.612,0:00:33.691 A long piece going into the limewater and a short piece which dosn't reach the limewater. 0:00:33.691,0:00:58.475 I'm going to Exhale air from my lungs into the limewater. And it should turn milky, once there is enough Carbon Dioxide... 0:00:58.475,0:01:09.644 As you can see, After about 15 secs blowing. The limewater has gone from clear to milky... 0:01:09.644,0:01:12.961 Indicating the presence of Carbon Dioxide. 0:01:12.961,0:01:18.302 I will now switch the stopper, with the tubing. From the testube on the left, to the one on the right. 0:01:18.302,0:01:23.307 This time. Rather than breathing out on the tube going into the limewater. We will inhale air through 0:01:23.307,0:01:33.153 the short tubing. The air is being drawn in from the room. And as it contains much less Carbon Dioxide 0:01:33.153,0:01:37.937 It will take longer for the Limewater to turn milky. 0:01:37.937,0:01:49.668 I will now suck through the short tube... 0:01:49.684,0:01:56.207 The amount of air that must pass through the limewater to turn it milky, takes considerately longer than 0:01:56.207,0:02:08.042 the one on the left. So, we will keep drawing in air until it turns milky... 0:02:08.042,0:02:12.517 As you can see. The limewater in this testube has eventually turned milky. But this is after 7 mins of 0:02:12.517,0:02:19.652 drawing in air from the room, into the limewater.This experiment shows that there is far more Carbon 0:02:19.652,0:02:29.516 Dioxide in Exhaled air. Than there is in Inhaled air. That's the end of Experiment OB11... 0:02:29.516,0:02:37.591 Experiment - OB49. To show that starch is produced by a photosynthesizing leaf. 0:02:37.591,0:02:40.177 Safety goggles, again. Must be worn. 0:02:40.177,0:02:49.004 In this Experiment, We take a leaf and we will test the presence of startch using the chemical Iodine. 0:02:49.004,0:02:53.585 The leaf must first be treated under several stages... 0:02:53.585,0:02:59.623 The first stage involves placing the leaf into a beaker of boiling water. For 1 min. 0:02:59.623,0:03:13.548 This helps to remove the the waxy qudicle from the leaf. The leaf is then removed from the boiling water 0:03:13.548,0:03:20.427 and placed into a testube of alcohol... 0:03:20.427,0:03:24.730 The alcohol will disolve the chylorphyl from the leaf, But the alcohol must be first be heated. 0:03:24.730,0:03:38.104 As alcohol is extremely flammable. It cannot be heated directly and must be heated in a water bath.. 0:03:38.104,0:03:50.123 The leaf is left in the alcohol in the water bath. Until all the chlorophyll has been removed... 0:03:50.123,0:03:54.885 After aprox. 10 min. The alcohol can be seen to have turn green in colour. This is because the chlorophyll 0:03:54.885,0:04:06.115 has disolved from the leaf into the alcohol. We now remove the alcohol from the water bath... 0:04:06.115,0:04:09.128 And place it on the testube rack.. 0:04:09.128,0:04:15.091 Because we no longer need to use the water bath, the Bunsen Burner can be switched off or the Chimney 0:04:15.091,0:04:23.230 can be closed, giving an orange flame. Which makes it easier to see and safer to use... 0:04:23.261,0:04:30.390 We now pour the alcohol out of the testube and remove the leaf from the testube... 0:04:30.390,0:04:43.351 We now remove the leaf from the testube, and place it into warm water to soften it. 0:04:43.351,0:04:47.875 5-10 secs is long enough... 0:04:47.875,0:05:09.071 The leaf is then spread on a white tile... And tested with the chemical Iodine... 0:05:09.071,0:05:11.789 This is the end of Experiment OB49... 0:05:11.789,0:05:18.709 Experiment - OB58. to investigate the conditions necessary for germination. 0:05:18.709,0:05:22.750 There are 3 factors, which must be present for seeds to germinate... 0:05:22.750,0:05:27.981 They are: Water, Oxygen and a suitable temperature. 0:05:27.981,0:05:36.153 Here we set up 4 testubes. The testube here, the seeds are placed on moist cotten wool, in an open testube 0:05:36.199,0:05:41.899 In a warm atmosphere. This is known as our control. 0:05:41.899,0:05:48.261 These seeds are in similar conditions, i.e: moist cotten wool with the presence of oxygen. 0:05:48.261,0:05:53.647 But this will be place in a fridge at 4 oC. 0:05:53.647,0:05:57.625 The seeds in this testube are placed in water that has been boiled and then cooled, which removes the 0:05:57.625,0:06:03.539 oxygen present in water. And a layer of oil is placed on top to prevent any further oxygen entering the 0:06:03.539,0:06:09.979 water... 0:06:09.979,0:06:17.579 The seeds in the last testube are placed on dry cotten wool, in a warm enviroment, in an open testube... 0:06:17.579,0:06:26.341 The testubes are going to be left like this for one week and we will return to them to see the results.. 0:06:26.341,0:06:32.982 One week has passed... And we return to look at the seeds in the testubes... 0:06:32.982,0:06:41.139 The seeds int his testube have germinated, this is because they had the 3 conditions needed: Water, Oxygen 0:06:41.139,0:06:46.173 & a suitable temperature... 0:06:46.173,0:06:53.911 The seeds in this testube did not germinate because the have been placed in a fridge at 4 oC... 0:06:53.911,0:07:00.513 Similarly. These seeds did not germinate, because they were in water that was boiled and cooled. 0:07:00.513,0:07:05.436 Hense they were not exposed to any oxygen. 0:07:05.436,0:07:12.421 And these seeds have not germinated because they were placed in dry cotten wool... 0:07:12.421,0:07:16.953 That is the end of experiment OB58... 0:07:16.953,0:07:24.139 Experiment - OB65. To investigate the presence of micro-organisms in air & in soil... 0:07:24.139,0:07:29.074 For this experiment, we used 3 petri dishes... 0:07:29.074,0:07:35.297 The first petri dish is our control. SO it remains sealed through out the experiment. 0:07:35.297,0:07:44.837 The second petri dish is going to be exposed to air. SO we remove the lid for aprox. 5 min... 0:07:44.837,0:07:53.044 The thrid dish we sprinkle a small amount of soil on the edgar inside the dish... 0:07:53.044,0:07:57.960 And put the lid back on as quickly as possible... 0:07:57.960,0:08:05.362 The 3 Petri dishes are now placed upside down in an incubator at 25 oC for aprox. 1 week... 0:08:05.362,0:08:14.634 1 week has passed. And we have removed the petri dishes from the incubator at 25 oC... 0:08:14.634,0:08:20.503 The first petri dish, which is our control, shows no growths or micro-organisms 0:08:20.503,0:08:25.162 Which means the dish itself was sterilized... 0:08:25.162,0:08:33.931 The second dish had been exposed to air for aprox. 5 min. It contains "a fluffy" or "moldy" growths. 0:08:33.931,0:08:44.140 This indicates the presence of fungi. The third dish which is exposed to small amount of soil shows 0:08:44.140,0:08:48.896 smooth, round growths. Which indicate the presence of bacteria. 0:08:48.896,0:08:56.713 And some "moldy" or "fluffy" growths, which indicate the presence of fungi... 0:08:56.713,9:59:59.000 That is the end of experiment OB65...