Activity Round
Activity
Took a pinch of wheat flour and moisten it with water and add a few drops of iodine solution.
Observation
The contents turn bluish.
Question
Why it so happens?
Answer
Wheat flour contains starch and starch gives blue colour with iodine.
Activity
1. Prepare water extract of a pinch of a chemical compound in a beaker.
2. Took a small quantity of the extract and added to it freshly prepared ferrous sulphate solution.
3. Now added conc. H
2
SO
4 by the sides of the test tube.
Observations
A dark brown ring is seen in the middle of the solution.
Question
What could be the nature of the compound used?
Answer
It is a ring test of Nitrate.
Activity
1.
Put lime water solution in a test tube
2. Blow air from the mouth through the solution with the help of a glass tube
Observation
The solution turn milky.
Question
1. Give the chemical name of the substance contained in the test tube.
2. State the reason of the contents of the tube turning milky.
Answer
1. The test tube contains Calcium hydroxide.
2. When air from the mouth is blown in the lime water, the Calcium hydroxide gets converted into
Calcium carbonate by reacting the
Carbon dioxide of the air from the mouth. The solution of Calcium carbonate is milky.
Activity
1. Gently lower an egg into a large glass of water. It will sink.
2. Remove the egg and put 10 table spoons of the salt in the water and dissolve it completely to make in the solution.
3. Put the egg in the solution.
Observations
In the pure water the egg sinks whereas in the water with the salt, the egg floats.
Questions
Reason out the observation and define the phenomenon involved.
Answer
1. The being denser than pure water sinks. On the other hand, the addition of the salt makes the water denser than the egg, so the egg floats.
2. Density is the mass of a substance per unit volume i.e.
d = M/V
Activity
1. Hold a postcard size paper between the thumb and the index finger in one hand.
2. Place the thumb & index finger of the other hand close to the other end of paper such that it does not touch the paper.
3. Release the paper and try to catch it with other hand.
4. Now ask your friend to catch the paper while you release it.
Observations
While you release the paper with one hand you can easily catch it with the other hand. However, your friend can not.
Question
Explain the reason.
Answer
When the same person holding the paper tries to catch it, it gets caught because the brain sends the impulse to the motor nerve to act on the muscles.
On the other hand when the person who is to catch the paper is different from the one who release it, the eyes of former (who is to catch) send the message through the eyes to the brain which in turn sends the impulse to the motor nerve to act to catch the paper. This takes longer time than in the first situation.
Activity:
Take a test tube and fill 3/4 th of it with water.
Hold the tube in an inclined position and heat the upper part of the water in it.
Observation:
The water at the upper level starts boiling. However, there is no difficulty in holding the tube from the lower end.
Question:
Why the lower end does not get hot?
Answer:
When water is heated even to the extent of boiling, it gets converted into steam that being lighter in weight, escapes out from the tube. So the water at the lower part of the tube remains unaffected by the heat
Activity
Take tow eggs – one fresh/raw and other hard boiled.
Give spin to both the eggs simultaneously on a horizontal plane surface.
Observation
One egg spins uniformly and the other vaguely.
Question
1. Distinguish between the raw and the hard boiled egg.
2. Give basis for your inference.
Answer
1. The egg that spins well is hard boiled while the other that spins vaguely is the raw one.
2. The raw egg does not spin well because the friction between the egg shell and the surface of the base gets impaired by the friction between the contents of the egg and the shell.
Activity
1. Take a small bucket filled half with water.
2. Put the bucket in circular motion with at a fast speed.
Observation
The water from the bucket does not fall even when it is inverted at the top of the round.
Question
Why water does not fall?
Answer
Water doesn’t fall because of the centrifugal force. It maintains the maximum distance between the object moving speedily in a circular path and the center of circle of rotation. The more the speed of rotation, the more will be the centrifugal force.
Activity
1. Take a cup and place a coin in it.
2. Look at it and starts moving away from it till the coin becomes out of sight.
3. Request some one to add water into the cup slowly till it is nearly filled.
Observation
You can again see the coin from the position from it was not visible earlier.
Question
What is the reason of reappearance of this coin?
Answer
The coin is visible in the cup because the light travels straight from the coin into your eyes but when you move away, the wall of he cup obstructs the path of light.
When the cup is filled with water, the ray of light traveling through the medium of water gets refracted when it enters the medium of air. The refracted image of he coin is thus, visible.
Activity
1. Take a thick paper and make its pot and fill about half with water.
2. Place it over a wire gauge on a tripod stand and heat it with flame.
Observation
Water gets warm up without burning the paper.
Question
Why the paper does not burn.
Answer
In an uncovered pot one can warm water only up to the boiling point i.e. 100 ºC. Water having great heat capacity, absorbs the papers’ extra heat and prevents it from warming more than 100 ºC, i.e. to a point where it could burst into flame.
Activity
Take a bar magnet near to the iron fillings.
Observation
:
The magnet attracts the iron fillings .
Question:
Why does it attract?
Answer:
In the magnet the half field spins of the atoms give us the domain of a tiny magnet, in bar magnet, these tiny magnets are arranged in a particular order that attracts the iron fillings to make the filling in the same order
Activity
Squeeze some lemon juice on a piece of chalk.
Observation
Fizzes appear on the chalk surface.
Question
Why does it so happen?
Answer
Fizzes appear due to production of gas.
Calcium carbonate of chalk reacts with weak acid and produces CO
2
Activity
Take two bar magnets.
Bring them together
Observation:
They either attract or repel each other.
Question:
Why it is so?
Answer:
Magnetic poles connect the magnets by their respective field lines. When the same pole come closer, the field lines repel each other that is why the like poles repel. While opposite poles take field lines from one pole to terminate to another pole.
Therefore, they attract each other.
Activity
Take a flask and cover its mouth with a balloon.
Heat the flask.
Observation
The balloon inflates
Question
Why it inflates?
Answer
When the flask is heated, the air inside it expands and becomes lighter and needs more space. It goes into the balloon which inflates.
Activity
1. Take two beakers of equal sizes.
2. Pour cold water in the one and the hot water in the other.
3. Put two drops of the dark ink in each beaker simultaneously.
Observation
In the beaker containing hot water in the ink dissolves readily than in the one having cold water.
Question
Reason out the observations and define the phenomenon behind this.
Answer
The reason behind this observation is the process of diffusion. It depends upon the concentration and nature of the solute and temperature. In the hot water due to high temperature, the kinetic energy of the solute molecules is more, thereby resulting in the fast dissolving of ink in hot water.
Diffusion is the movement of the solute from higher conc. to lower conc.
Activity
Put a stamp on the table and place a glass beaker containing water over it.
Cover it with saucer.
Observation
The stamp disappears irrespective of the direction from where we try to see.
Question
Why does stamp disappear?
Answer
The principle of Refraction governs the phenomenon involved. The incident light while entering from the rarer to the denser medium bends towards the normal, and moves away from normal when it comes from denser to rarer medium.
When we look from the side, the angles formed are such that the stamp becomes invisible.
Activity
Took a glass of water. Pour a drop of honey from two different samples
Observation
One of the samples shows a fibrous streak of honey while the other dissolves without forming the honey thread.
Question
What inference is drawn?
Answer
The pure honey has a higher viscosity and takes more time in dissolution, while the honey adulterated with sugar dissolves easily because of water content contained in sugar solution.
Activity
1. Take a pencil torch and a laser pointer.
2. Switch these on simultaneously and throw the light on wall/screen.
Observation
The torch light will show a wider spot, while the laser light will show a narrow spot.
Question
What is the principle behind this phenomenon?
Answer
In case of Laser, the quanta of light photon get aligned by the stimulation of photons and we obtain monochromatic and coherent beam while the light emitted from the torch neither monochromatic and nor coherent.
Activity
1 . Tie a metal coat hanger in the centre with a piece of rope.
2. Tie one end of the rope three or four times around your left finger and other end to your right finger.
3. Put the ends of your fingers into your ears.
4. Strike the coat-hanger against a chair.
Observation:
You will hear some beautiful music.
Question
Why it is so?
Answer
The music is heard because the coat-hanger vibrates. The rope and your fingers bring the sound waves to your ears
Activity
Take a pinch of material in a test tube and add Fehling solution A and B in equal amounts.
Heat the contents.
Observation
Formation of Red precipitates.
Question
Tell the chemical nature of the compound.
Answer
Presence of Reducing sugar
(Free or potentially free aldehyde or ketone group).
Reducing sugar give red coloured cuprous oxide in alkaline medium.
Activity
1.
Take some amount of sodium carbonate in a balloon and acetic acid in a test tube.
2. Cover the mouth of test tube with the balloon and invert the contents from the balloon.
Observation
The balloon increases in volume.
Questions
Why it so happens?
Give the reaction for the observed phenomena.
Answer
The balloon increases in volume due to the upward movement of the gas formed in the test tube.
The sodium carbonate reacts with acetic acid and produces CO2 which moves up and causes an increase in volume of balloon.
2CH
3
COOH + Na
2
CO
3
2CH
3
COONa + CO
2
+ H
2
O
Activity
1 . Shake 0.5 gm of compound with 1-2 ml of water.
2. Add few drops of 10% α-Naphthol.
3. Add conc. H
2
SO
4 along the side of the tube.
Observation
Formation of purple coloured ring on the junction of two liquids.
Question
What is the functional group of the compound?
Answer
Carbohydrates are converted to furfural which reacts with α-
Naphthol to give purple colour.
Activity
Take 1-2 ml of compound in a test tube.
Add Bromine water to the test tube.
Observation
Formation of white precipitates.
Question
What is the functional group of the compound.
Answer :
Phenol
White precipitates are formed due to the formation of
Tribromophenol.
Activity
Take a beaker with water in it and put some drops of fountain pen ink.
Observation
The water in the beaker will slowly attains the colour of the ink.
Question
Which phenomenon is governing this? Explain it.
Answer
Process of diffusion governs it.
It states that the solute molecules will tend to move from a region of higher concentration in an open medium till the equilibrium is achieved.
Activity
Take Ammonium dichromate in a watch glass.
Add few drops of ethyl alcohol to moisten it.
Ignite it.
Observation
After burning, an eruption like a volcano is seen
Question
Why does it happens so?
Answer
It is a highly exothermic reaction and oxide in the form of ash that as result forms a heap like that of a volcano.
Activity
Dip a glass rod in a solution of an organic compound and bring it on to the flame.
Observation
It gives smoky flame.
Question
What category of organic compound it was?
Answer
Aromatic compounds give smoky flame.
Activity
Dip a glass rod in a solution of an organic compound and bring it on to the flame.
Observation
No change in the could be seen.
Question
What category of organic compound it was?
Answer
Aliphatic compounds do not give smoky flame.
Activity
Squeeze some lemon juice on a piece of chalk.
Observation
Fizzes appear on the chalk surface.
Question
Why does it so happen?
Answer
Fizzes appear due to production of gas.
Calcium carbonate of chalk reacts with weak acid and produces CO
2
Activity
Place crystals of Potassium permanganate in a dish and add a few drops of Glycerin.
Put a few paper clippings over it and wait.
Observation
After some time smoke followed by flame is seen.
Question
Why does the paper burn without any external help?
Answer
Glycerin in contact with
Potassium permanganate, results in a highly exothermic reaction so strong that the paper gets ignited.
Activity
1.Take three different types of soils.
2. Put 20 g of each soil type in 50 ml of water and make a slurry.
3. Dip a strip of the red/blue litmus paper in the slurry.
Observations
In one soil the blue litmus paper turns red, whereas in the other red turns blue while in the third one it remains unchanged.
Questions
1. Why the litmus paper changes colour and why not?
2. Name the phenomenon responsible for the observed change and define.
Answer
1. In one case where the litmus turns
Red, the soil is Acidic; in the other where litmus turns Blue, the soil is alkaline; while the one where litmus changes no colour, the soil is neutral.
2. The phenomenon responsible is pH. Ph is the negative logarithmic of the H + ion concentration.
Activity
1. Three beakers are filled with water.
2. Measure the purity of each and arrange the samples accordingly using conductivity of each.
Question
Which water is more pure and why.
Answer
The water with least conductivity is more pure.
Because less conductivity means lesser number of dissolved ions and so lesser flow of ions / current
Activity
Take few drops of an organic compound in water and add 1-2 drops of neutral ferric chloride.
Observation
Appearance of blue colour.
Question
What is the functional group of the compound?
Answer : Phenolic group
Neutral ferric chloride reacts with phenolic compounds to form ferric phenoxides, which have characteristics colours depending upon the nature of the phenolic compounds.
Here it was p-Cresol.
Activity
Hold a piece of paper horizontally close to your mouth/lips.
Blow across the top of the paper as it hangs down from hands in front of lips.
Observation
The paper will respond by moving up, toward the stream of moving air.
It would seem the paper would move away from the stream of air, but it moves toward the stream of air.
Question
Name the principle involved in the process
Answer
Bernoulli's Principle
Activity
Take a lemon; insert a copper wire and carbon rod in it.
Tie both the carbon and the copper wire to cathode and anode of the Galvanometer.
Observation
Galvanometer shows deflection.
Question
Why does it deflect?
Answer
Lemon contains citric acid which acts as electrolyte.
Copper and Carbon act as electrodes.
So, electrons flow from cathode to anode and as a result current flows. Thus Galvanometer shows deflection.
Activity
1 . Sit up-right/straight in your chair with legs straight down with legs bending at knees at approx
90 o angle and the feet together.
2. Without changing the place of your feet and without bending forward try to get up.
Observation
You can not get up unless you bend forward or take or move your feet under the chair.
Question
Why you could not get up without bending forward or changing the position of your feet.
Answer
For equilibrium, we know that the line perpendicular to the centre of Gravity must fall through its base.
By bending forward, the position of the centre of gravity is changed so that it falls through the base of the body. Till it is done the equilibrium which is essential for stability is not achieved and thus one can not get up unless one bends forward. Similarly by changing the position of the feet and bringing them under the chair, the base of the body is moved so that the line falling from the centre of the body falls through it.
Activity
Take a glass full of water.
Take a needle on a piece of blotting paper and place it gently over the water surface.
Observation
Blotting paper soaks water and sinks down but the needle keeps floating.
Question
What do you observe and why is it so?
Answer
Answer
It is because of surface tension. The molecules of water adhere together due to surface tension forming a thin membrane on surface.
