Experiments with water
By M. Ramakrishnan
Mystery of floating and sinking… CBSE, E.V.S. Class – V, Unit – 7
- Identify the objects that float and sink in water.
- Experiment and classify the objects that are soluble and insoluble in water.
- Understand the similarities and differences between water, oil, milk, cold drinks etc.
- Understand the concept of evaporation.
Floating and Solubility in water
Sources and uses of water
- Video clips
- Glass tumbler
- Story cards
Activity 1 - Story
The teacher narrates the story of the donkey and the cotton bag using story cards. Students listen to the story.
Activity 2 - Magic lemon
Two glasses of water will be kept in front of the students. One of the glasses will have salt in it (children need not know this). Drop a lemon into the glass of plain water and ask students to predict the outcome. The lemon sinks. Next, drop the lemon into the salt water and students will be surprised to see that the lemon floats. The teacher needs to build the excitement by asking questions and encouraging students to find out answers.
Activity 3 – Paper boats
Teacher asks the students to make a colour paper boat and put it in water. It floats. Now place a chalk piece in the boat. The paper boat continues to float. Add chalk pieces one by one until the paper boat sinks. Ask students to guess the reason behind this. Students can be asked certain to share their views on why certain objects float on water while others sink. What would happen to a steel vessel when it is put in water? Students observe, think and answer these questions.
Some of the hands on activities mentioned below will help children explore concepts like sinking and floating, solubility and insolubility, viscosity and evaporation. Worksheets are also included.
Activity 1: What floats and sinks
The teacher forms groups of four students. Each group will require a big bucket filled with water and some materials. (Refer textbook page 62) Students are asked to drop the material one by one into the bucket and observe what happens. Their observations can be recorded in the worksheet given in the text book.
(Hint: Teacher instructs the students in advance to bring the materials for the activity.)
Activity 2: Lemon in salt water
One group can be asked to do this experiment while the others observe. Take a glass of water and put a lemon in it. Now keep adding salt in the water, halfa-spoon at a time. What happens?Teacher probes further by askingthem the following questions. Why does the lemon float in salt water? Why doesn’t it float in plain water? Students observe the experiment and note down the observation in their books.
Activity 3: Soluble and insoluble substances
The class is divided into groups of four students to perform this experiment. The activity requires 4 – 5 glasses or bowls, spoons, water and some materials - (Refer page 64 in the textbook.) Take some water in each glass and try to dissolve one item in one glass. Observe and record what happens. This can be made more exciting for children if they are allowed to try it with materials of their choice. Teacher then asks them question like:
- Could you see the salt after it dissolved in water? Why?
- Was there any difference between the water glasses that had salt and chalk power?
- Which of the two would you be able to filter using a cloth – salt or chalk powder?
Students carry out the experiment, note their observations and answer the questions.
Activity 4: Which fluid flows faster?
Teacher can ask one student to do this activity and the others to observe it. Put two drops of oil on the lid of the tiffin box. Put two drops of water and two drops of sugar solution adjacent to it. Then tilt the lid to notice some drops slide down quickly. Which of the droplets slide down faster? Why? Students share their explanations.
The teachers asks students to give their explanation for the following questions.
1. The aluminum foil _________in water when it was spread into a sheet and __________ when it was made into a ball.
2. The lemon floats in salted water because _____________________
3. Do you think oil gets dissolved in the water? Why do you think so?
Why do materials float or sink?
The simple answer is due to buoyancy. Any material that floats on water has more buoyancy, because the upward thrust of the water is greater than the downward thrust of the material.Initially, children may come up with various explanations for an experiment; the nail is small, the soap is big, the pin is heavy, the match stick is lighter, there is more water, the glass is small etc. Teachers should not dismiss their answers as wrong. Instead, they could probe further until students arrive at the correct explanation. The teacher can then summarize that floating of an object will depend on its weight, shape, thickness and density.
Solubility - It is the ability of any substance to dissolve in a liquid. Water is a universal solvent and it dissolves more materials than any other liquid.
Fluid flow – Viscosity of a liquid determines its flow. Viscosity is the resistance caused due to the frictional movement of the molecules within the fluid. The objective of activity - 4 was to help students explore the behavior of different fluids.
Activity 1- Objects floating in Dead Sea
The teacher screens the video of a man floating in Dead Sea. There are plenty of videos available online. It is ideal to choose a short video, not longer than a minute. After watching the video, teacher explains that most objects will float inDead Sea and humans will appear as if they are lying down on water. This can be connected with the lemon in salt water experiment. As an additional activity, teacher can show them the video of salt formation in the seashore and talk about Gandhiji’s Dandi march. The class discusses why this was important, how such a simple idea brought people together and what does it mean to have freedom. Some real like scenarios can be given to students to apply their understanding of the concept.
- You have washed your handkerchief and you want to dry it quickly. What will you do?
- What do you put in water to make tea? Which of those dissolve in water?
- You have been given some lumps of sugar. Suggest some ways to quickly dissolve it.
Teacher gives the worksheet to each children and asks them to fill it.
1. Worksheet - 1
Term: Term 1