1 00:00:00,000 --> 00:00:06,006 Experiment - OB11. To compare the levels of Carbon Dioxide in Inhaled & Exhaled Air. 2 00:00:06,022 --> 00:00:12,622 Safety googles and gloves must always be worn, when chemicals are involved. 3 00:00:12,622 --> 00:00:20,572 We have 2 testubes containing limewater. Limewater is a clear solution and it turns milky when Carbon 4 00:00:20,572 --> 00:00:24,527 Dioxide is present... 5 00:00:24,527 --> 00:00:27,612 The testube on the left, contains a stopper which has 2 pieces of tubing. 6 00:00:27,612 --> 00:00:33,691 A long piece going into the limewater and a short piece which dosn't reach the limewater. 7 00:00:33,691 --> 00:00:58,475 I'm going to Exhale air from my lungs into the limewater. And it should turn milky, once there is enough Carbon Dioxide... 8 00:00:58,475 --> 00:01:09,644 As you can see, After about 15 secs blowing. The limewater has gone from clear to milky... 9 00:01:09,644 --> 00:01:12,961 Indicating the presence of Carbon Dioxide. 10 00:01:12,961 --> 00:01:18,302 I will now switch the stopper, with the tubing. From the testube on the left, to the one on the right. 11 00:01:18,302 --> 00:01:23,307 This time. Rather than breathing out on the tube going into the limewater. We will inhale air through 12 00:01:23,307 --> 00:01:33,153 the short tubing. The air is being drawn in from the room. And as it contains much less Carbon Dioxide 13 00:01:33,153 --> 00:01:37,937 It will take longer for the Limewater to turn milky. 14 00:01:37,937 --> 00:01:49,668 I will now suck through the short tube... 15 00:01:49,684 --> 00:01:56,207 The amount of air that must pass through the limewater to turn it milky, takes considerately longer than 16 00:01:56,207 --> 00:02:08,042 the one on the left. So, we will keep drawing in air until it turns milky... 17 00:02:08,042 --> 00:02:12,517 As you can see. The limewater in this testube has eventually turned milky. But this is after 7 mins of 18 00:02:12,517 --> 00:02:19,652 drawing in air from the room, into the limewater.This experiment shows that there is far more Carbon 19 00:02:19,652 --> 00:02:29,516 Dioxide in Exhaled air. Than there is in Inhaled air. That's the end of Experiment OB11... 20 00:02:29,516 --> 00:02:37,591 Experiment - OB49. To show that starch is produced by a photosynthesizing leaf. 21 00:02:37,591 --> 00:02:40,177 Safety goggles, again. Must be worn. 22 00:02:40,177 --> 00:02:49,004 In this Experiment, We take a leaf and we will test the presence of startch using the chemical Iodine. 23 00:02:49,004 --> 00:02:53,585 The leaf must first be treated under several stages... 24 00:02:53,585 --> 00:02:59,623 The first stage involves placing the leaf into a beaker of boiling water. For 1 min. 25 00:02:59,623 --> 00:03:13,548 This helps to remove the the waxy qudicle from the leaf. The leaf is then removed from the boiling water 26 00:03:13,548 --> 00:03:20,427 and placed into a testube of alcohol... 27 00:03:20,427 --> 00:03:24,730 The alcohol will disolve the chylorphyl from the leaf, But the alcohol must be first be heated. 28 00:03:24,730 --> 00:03:38,104 As alcohol is extremely flammable. It cannot be heated directly and must be heated in a water bath.. 29 00:03:38,104 --> 00:03:50,123 The leaf is left in the alcohol in the water bath. Until all the chlorophyll has been removed... 30 00:03:50,123 --> 00:03:54,885 After aprox. 10 min. The alcohol can be seen to have turn green in colour. This is because the chlorophyll 31 00:03:54,885 --> 00:04:06,115 has disolved from the leaf into the alcohol. We now remove the alcohol from the water bath... 32 00:04:06,115 --> 00:04:09,128 And place it on the testube rack.. 33 00:04:09,128 --> 00:04:15,091 Because we no longer need to use the water bath, the Bunsen Burner can be switched off or the Chimney 34 00:04:15,091 --> 00:04:23,230 can be closed, giving an orange flame. Which makes it easier to see and safer to use... 35 00:04:23,261 --> 00:04:30,390 We now pour the alcohol out of the testube and remove the leaf from the testube... 36 00:04:30,390 --> 00:04:43,351 We now remove the leaf from the testube, and place it into warm water to soften it. 37 00:04:43,351 --> 00:04:47,875 5-10 secs is long enough... 38 00:04:47,875 --> 00:05:09,071 The leaf is then spread on a white tile... And tested with the chemical Iodine... 39 00:05:09,071 --> 00:05:11,789 This is the end of Experiment OB49... 40 00:05:11,789 --> 00:05:18,709 Experiment - OB58. to investigate the conditions necessary for germination. 41 00:05:18,709 --> 00:05:22,750 There are 3 factors, which must be present for seeds to germinate... 42 00:05:22,750 --> 00:05:27,981 They are: Water, Oxygen and a suitable temperature. 43 00:05:27,981 --> 00:05:36,153 Here we set up 4 testubes. The testube here, the seeds are placed on moist cotten wool, in an open testube 44 00:05:36,199 --> 00:05:41,899 In a warm atmosphere. This is known as our control. 45 00:05:41,899 --> 00:05:48,261 These seeds are in similar conditions, i.e: moist cotten wool with the presence of oxygen. 46 00:05:48,261 --> 00:05:53,647 But this will be place in a fridge at 4 oC. 47 00:05:53,647 --> 00:05:57,625 The seeds in this testube are placed in water that has been boiled and then cooled, which removes the 48 00:05:57,625 --> 00:06:03,539 oxygen present in water. And a layer of oil is placed on top to prevent any further oxygen entering the 49 00:06:03,539 --> 00:06:09,979 water... 50 00:06:09,979 --> 00:06:17,579 The seeds in the last testube are placed on dry cotten wool, in a warm enviroment, in an open testube... 51 00:06:17,579 --> 00:06:26,341 The testubes are going to be left like this for one week and we will return to them to see the results.. 52 00:06:26,341 --> 00:06:32,982 One week has passed... And we return to look at the seeds in the testubes... 53 00:06:32,982 --> 00:06:41,139 The seeds int his testube have germinated, this is because they had the 3 conditions needed: Water, Oxygen 54 00:06:41,139 --> 00:06:46,173 & a suitable temperature... 55 00:06:46,173 --> 00:06:53,911 The seeds in this testube did not germinate because the have been placed in a fridge at 4 oC... 56 00:06:53,911 --> 00:07:00,513 Similarly. These seeds did not germinate, because they were in water that was boiled and cooled. 57 00:07:00,513 --> 00:07:05,436 Hense they were not exposed to any oxygen. 58 00:07:05,436 --> 00:07:12,421 And these seeds have not germinated because they were placed in dry cotten wool... 59 00:07:12,421 --> 00:07:16,953 That is the end of experiment OB58... 60 00:07:16,953 --> 00:07:24,139 Experiment - OB65. To investigate the presence of micro-organisms in air & in soil... 61 00:07:24,139 --> 00:07:29,074 For this experiment, we used 3 petri dishes... 62 00:07:29,074 --> 00:07:35,297 The first petri dish is our control. SO it remains sealed through out the experiment. 63 00:07:35,297 --> 00:07:44,837 The second petri dish is going to be exposed to air. SO we remove the lid for aprox. 5 min... 64 00:07:44,837 --> 00:07:53,044 The thrid dish we sprinkle a small amount of soil on the edgar inside the dish... 65 00:07:53,044 --> 00:07:57,960 And put the lid back on as quickly as possible... 66 00:07:57,960 --> 00:08:05,362 The 3 Petri dishes are now placed upside down in an incubator at 25 oC for aprox. 1 week... 67 00:08:05,362 --> 00:08:14,634 1 week has passed. And we have removed the petri dishes from the incubator at 25 oC... 68 00:08:14,634 --> 00:08:20,503 The first petri dish, which is our control, shows no growths or micro-organisms 69 00:08:20,503 --> 00:08:25,162 Which means the dish itself was sterilized... 70 00:08:25,162 --> 00:08:33,931 The second dish had been exposed to air for aprox. 5 min. It contains "a fluffy" or "moldy" growths. 71 00:08:33,931 --> 00:08:44,140 This indicates the presence of fungi. The third dish which is exposed to small amount of soil shows 72 00:08:44,140 --> 00:08:48,896 smooth, round growths. Which indicate the presence of bacteria. 73 00:08:48,896 --> 00:08:56,713 And some "moldy" or "fluffy" growths, which indicate the presence of fungi... 74 00:08:56,713 --> 99:59:59,999 That is the end of experiment OB65...