| Earth & Space - Materials from Earth - The Earth & its Resources - G15 |
  Teacher's Guide
ES-D2.4 |
|
|
|
1. To obtain soil samples you may have to ask around to see if anyone has a different soil to that of the school or your garden. Grow bags or commercial soils such as John Innes No.1 are another useful source although often artificially mixed. You can add sand to this to make a more sandy soil. To investigate the contents of the soil you could try adding water to it in small lemonade bottles. Shake this vigorously then leave overnight to settle. This way the larger particles will sink to the bottom and the small ones settle on top. You can now examine the layers through the bottle. (Check with Health and Safety - you may not be allowed to let the children handle garden soil because of the bacteria etc. which may be present.) Commercially prepared soils are usually sterilised to prevent spread of plant diseases and so may be better to use.) |
| 2. To do this you would need to soak the pre-weighed soil samples overnight then filter them to remove excess water and weigh the remaining soil to see how much water has been taken up. Alternatively place a measured amount of soil into a petri dish and pour on a measured amount of water. After a few hours, observe the samples and see if any have water still lying in the dish and tilt them to see if there is water that can be poured off. |
|
3. This is difficult to do in a classroom because you would need a fairly accurate balance and school scales are often not in that category! Weigh soil samples of say 50 gm and spread out in petri dishes somewhere warm and dry with a good airflow. After a few days reweigh the sample and see how much water they have lost. If you have an oven you could bake the samples instead.
Worksheet D6 (G) is a results sheet for the children to record the soil water content and if their maths is up to it they could work out the percentage water content. |
