On Friday 29th June, we did a practical experiment in the lab. Before we carried out the experiment we recapped on what we knew about living things on Google Docs, here's the link: http://goo.gl/g35sa. For the experiment, we were given 5 unknown substances A, B, C, D and E and were to find out whether they were alive. Here are the steps to the experiment:
1. Label the tube A, B, C, D and E.
2. Carefully transfer 1 spatula full of each of the substance A, B, C, D and E into the respective test tube.
3. Add 3ml of water to each test tube. mix well using the wooden splinter.
4. Start your stopwatch.
5. Observe. Write your observations in table 1. Take readings if you have to.
6. After 10 mins, record the observation again.
7. What is your inference for each of the substance? is there any evidence of life?
Physical appearances of substances A, B, C, D and E:
A: Looks like sand
B: Long, thin particles
C: Circular and transparent
D: Roundish, some brown, some purple
E: Very small dark brown particles
Changes observed after 10 mins:
A: Particles clamp together at the bottom and water becomes murky
B: Substance dissolved in water
C: Substance expanded. Somewhat looks like particles fused together.
D: Little silvery bubble-like "extensions" appear on substance.
E: About half sinks, half floats, a small part of it suspended.
Three different types of liquids - water, glucose and salt water are also provided to test the reactions of the substances to the liquids. Why were these liquids chosen?
This is because glucose is a type of sugar that is an important source of energy to living organisms. Thus, if any of the substances were alive, they may show some sort of reaction after coming into contact with glucose. Water provides dissolved oxygen for the substances if they are alive. As for salt water, if the substance can only survive in salt water, then it would only react to the salt water and not the other two liquids.
1. Label the tube A, B, C, D and E.
2. Carefully transfer 1 spatula full of each of the substance A, B, C, D and E into the respective test tube.
3. Add 3ml of water to each test tube. mix well using the wooden splinter.
4. Start your stopwatch.
5. Observe. Write your observations in table 1. Take readings if you have to.
6. After 10 mins, record the observation again.
7. What is your inference for each of the substance? is there any evidence of life?
Physical appearances of substances A, B, C, D and E:
A: Looks like sand
B: Long, thin particles
C: Circular and transparent
D: Roundish, some brown, some purple
E: Very small dark brown particles
Changes observed after 10 mins:
A: Particles clamp together at the bottom and water becomes murky
B: Substance dissolved in water
C: Substance expanded. Somewhat looks like particles fused together.
D: Little silvery bubble-like "extensions" appear on substance.
E: About half sinks, half floats, a small part of it suspended.
Three different types of liquids - water, glucose and salt water are also provided to test the reactions of the substances to the liquids. Why were these liquids chosen?
This is because glucose is a type of sugar that is an important source of energy to living organisms. Thus, if any of the substances were alive, they may show some sort of reaction after coming into contact with glucose. Water provides dissolved oxygen for the substances if they are alive. As for salt water, if the substance can only survive in salt water, then it would only react to the salt water and not the other two liquids.
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