Activity 5.7:
Aim: To study various water purification methods.
Materials: Pond water, chlorine water, sterile nutrient agar, filter paper and cellophane tape
Apparatus: Beaker, glass rod, filter funnel, measuring cylinder, Bunsen burner, wire gauze, Petri dish, distillation flask, Liebig condenser, retort stand with clamp, thermometer and one-hole rubber stopper
Instruction
1. Set up the apparatus as shown in Figure 5.21(a) and collect the filtrate.
2. Set up the apparatus as shown in Figure 5.21(b) and collect the distillate.
3. Prepare five Petri dishes containing nutrient agar and label them as A, B, C, D and E.
4. Add the following substances into the Petri dishes.
Petri dish A is added with five drops of pond water
Petri dish B is added with five drops of filtrate of pond water
Petri dish C is added with five drops of distillate of pond water
Petri dish D is added with five drops of boiled pond water
Petri dish E is added with five drops of pond water mixed with chlorine water
5. Close all the Petri dishes and seal them with cellophane tape.
6. Keep all the Petri dishes in a dark place for four days.
7. After four days, observe and record the growth of microorganisms on the nutrient agar.
Observation
Questions
1. Which method produces pure water?
2. What is the function of chlorine in Petri dish E?
3. Give an inference for your observation on the nutrient agar in Petri dishes B and C.
Answer:
1. Distillation
2. Chlorine kills the microorganisms in the water in Petri dish E.
3. The nutrient agar in Petri dish B contains microbial colonies because filtration only removes suspended particles but not microorganisms. The nutrient agar in Petri dish C is free from microorganisms because distillation removes suspended particles, dissolved substances and microorganisms.
Aim: To study various water purification methods.
Materials: Pond water, chlorine water, sterile nutrient agar, filter paper and cellophane tape
Apparatus: Beaker, glass rod, filter funnel, measuring cylinder, Bunsen burner, wire gauze, Petri dish, distillation flask, Liebig condenser, retort stand with clamp, thermometer and one-hole rubber stopper
Instruction
1. Set up the apparatus as shown in Figure 5.21(a) and collect the filtrate.
2. Set up the apparatus as shown in Figure 5.21(b) and collect the distillate.
3. Prepare five Petri dishes containing nutrient agar and label them as A, B, C, D and E.
4. Add the following substances into the Petri dishes.
Petri dish A is added with five drops of pond water
Petri dish B is added with five drops of filtrate of pond water
Petri dish C is added with five drops of distillate of pond water
Petri dish D is added with five drops of boiled pond water
Petri dish E is added with five drops of pond water mixed with chlorine water
5. Close all the Petri dishes and seal them with cellophane tape.
6. Keep all the Petri dishes in a dark place for four days.
7. After four days, observe and record the growth of microorganisms on the nutrient agar.
Observation
Questions
1. Which method produces pure water?
2. What is the function of chlorine in Petri dish E?
3. Give an inference for your observation on the nutrient agar in Petri dishes B and C.
Answer:
1. Distillation
2. Chlorine kills the microorganisms in the water in Petri dish E.
3. The nutrient agar in Petri dish B contains microbial colonies because filtration only removes suspended particles but not microorganisms. The nutrient agar in Petri dish C is free from microorganisms because distillation removes suspended particles, dissolved substances and microorganisms.