audio
audioduration (s)
1.37
22.3
path
stringlengths
221
234
sentence
stringlengths
5
298
length
float32
5
5
train/chapter 1 1-46 (1).mp3
Chemical Reactions and Equations
5.003
train/chapter 1 1-46 (10).mp3
We have already learnt about physical and chemical changes of matter in our previous classes.
5.003
train/chapter 1 1-46 (11).mp3
Whenever a chemical change occurs, we can say that a chemical reaction has taken place.
5.003
train/chapter 1 1-46 (12).mp3
You may perhaps be wondering as to what is actually meant by a chemical reaction.
5.003
train/chapter 1 1-46 (13).mp3
How do we come to know that a chemical reaction has taken place?
5.003
train/chapter 1 1-46 (14).mp3
Let us perform some activities to find the answer to these questions.
5.003
train/chapter 1 1-46 (15).mp3
CAUTION:
5.003
train/chapter 1 1-46 (16).mp3
This Activity needs the teacher’s assistance.
5.003
train/chapter 1 1-46 (17).mp3
It would be better if students wear eye protection.
5.003
train/chapter 1 1-46 (18).mp3
Clean a magnesium ribbon about 2 cm long by rubbing it with sandpaper.
5.003
train/chapter 1 1-46 (19).mp3
Hold it with a pair of tongs.
5.003
train/chapter 1 1-46 (2).mp3
Consider the following situations of daily life and think what happens when –
5.003
train/chapter 1 1-46 (20).mp3
Burn it using a spirit lamp or burner and collect the ash so formed in a watch-glass.
5.003
train/chapter 1 1-46 (21).mp3
Burn the magnesium ribbon keeping it as far as possible from your eyes.
5.003
train/chapter 1 1-46 (22).mp3
What do you observe?
5.003
train/chapter 1 1-46 (23).mp3
Burning of a magnesium ribbon in air and collection of magnesium oxide in a watch-glass
5.003
train/chapter 1 1-46 (24).mp3
You must have observed that magnesium ribbon burns with a dazzling white flame and changes into a white powder.
5.003
train/chapter 1 1-46 (25).mp3
This powder is magnesium oxide.
5.003
train/chapter 1 1-46 (26).mp3
It is formed due to the reaction between magnesium and oxygen present in the air.
5.003
train/chapter 1 1-46 (27).mp3
Take lead nitrate solution in a test tube.
5.003
train/chapter 1 1-46 (28).mp3
Add potassium iodide solution to this.
5.003
train/chapter 1 1-46 (29).mp3
What do you observe?
5.003
train/chapter 1 1-46 (3).mp3
milk is left at room temperature during summers.
5.003
train/chapter 1 1-46 (30).mp3
Take a few zinc granules in a conical flask or a test tube.
5.003
train/chapter 1 1-46 (31).mp3
Add dilute hydrochloric acid or sulphuric acid to this.
5.003
train/chapter 1 1-46 (32).mp3
Do you observe anything happening around the zinc granules?
5.003
train/chapter 1 1-46 (33).mp3
Touch the conical flask or test tube. Is there any change in its temperature?
5.003
train/chapter 1 1-46 (34).mp3
From the above three activities, we can say that any of the following observations helps us to determine whether a chemical reaction has taken place –
5.003
train/chapter 1 1-46 (35).mp3
change in state
5.003
train/chapter 1 1-46 (36).mp3
change in colour
5.003
train/chapter 1 1-46 (37).mp3
evolution of a gas
5.003
train/chapter 1 1-46 (38).mp3
change in temperature.
5.003
train/chapter 1 1-46 (39).mp3
As we observe the changes around us, we can see that there is a large variety of chemical reactions taking place around us.
5.003
train/chapter 1 1-46 (4).mp3
an iron tawa/pan/nail is left exposed to humid atmosphere.
5.003
train/chapter 1 1-46 (40).mp3
We will study about the various types of chemical reactions and their symbolic representation in this Chapter.
5.003
train/chapter 1 1-46 (41).mp3
Formation of hydrogen
5.003
train/chapter 1 1-46 (42).mp3
when a magnesium ribbon is burnt in gas by the action of dilute sulphuric acid on oxygen, it gets converted to magnesium oxide.
5.003
train/chapter 1 1-46 (5).mp3
grapes get fermented.
5.003
train/chapter 1 1-46 (6).mp3
food is cooked.
5.003
train/chapter 1 1-46 (7).mp3
food gets digested in our body.
5.003
train/chapter 1 1-46 (8).mp3
we respire.
5.003
train/chapter 1 1-46 (9).mp3
In all the above situations, the nature and the identity of the initial substance have somewhat changed.
5.003
train/chapter 1 112-151 (1).mp3
Do you feel any change in temperature?
5.003
train/chapter 1 112-151 (10).mp3
Let us discuss some more examples of combination reactions.
5.003
train/chapter 1 112-151 (11).mp3
In simple language we can say that when two or more substances (elements or compounds) combine to form a single product, the reactions are called combination reactions.
5.003
train/chapter 1 112-151 (12).mp3
we also observed that a large amount of heat is evolved.
5.003
train/chapter 1 112-151 (13).mp3
This makes the reaction mixture warm.
5.003
train/chapter 1 112-151 (14).mp3
Reactions in which heat is released along with the formation of products are called exothermic
5.003
train/chapter 1 112-151 (15).mp3
chemical reactions.
5.003
train/chapter 1 112-151 (16).mp3
We all know that we need energy to stay alive.
5.003
train/chapter 1 112-151 (17).mp3
We get this energy from the food we eat.
5.003
train/chapter 1 112-151 (18).mp3
During digestion, food is broken down into simpler substances.
5.003
train/chapter 1 112-151 (19).mp3
For example, rice, potatoes and bread contain carbohydrates.
5.003
train/chapter 1 112-151 (2).mp3
Formation of slaked lime by the reaction of calcium oxide with Calcium oxide reacts vigorously with water to produce slaked lime water (calcium hydroxide) releasing a large amount of heat.
5.003
train/chapter 1 112-151 (20).mp3
These carbohydrates are broken down to form glucose.
5.003
train/chapter 1 112-151 (21).mp3
This glucose combines with oxygen in the cells of our body and provides energy.
5.003
train/chapter 1 112-151 (22).mp3
The decomposition of vegetable matter into compost is also an example of an exothermic reaction.
5.003
train/chapter 1 112-151 (23).mp3
Decomposition Reaction
5.003
train/chapter 1 112-151 (24).mp3
Take about 2 g ferrous sulphate crystals in a dry boiling tube.
5.003
train/chapter 1 112-151 (25).mp3
Note the colour of the ferrous sulphate crystals.
5.003
train/chapter 1 112-151 (26).mp3
Heat the boiling tube over the flame of a burner or spirit lamp.
5.003
train/chapter 1 112-151 (27).mp3
Observe the colour of the crystals after heating.
5.003
train/chapter 1 112-151 (28).mp3
Have you noticed that the green colour of the ferrous sulphate crystals?
5.003
train/chapter 1 112-151 (29).mp3
Correct way of heating the boiling tube has changed.
5.003
train/chapter 1 112-151 (3).mp3
In this reaction, calcium oxide and water combine to form a single product, calcium hydroxide.
5.003
train/chapter 1 112-151 (30).mp3
You can also smell the characteristic odour of burning containing crystals sulphur of ferrous sulphate.
5.003
train/chapter 1 112-151 (31).mp3
Ferrous sulphate crystals lose water when heated and the colour of the crystals changes.
5.003
train/chapter 1 112-151 (32).mp3
It then decomposes to ferric oxide, sulphur dioxide and sulphur trioxide.
5.003
train/chapter 1 112-151 (33).mp3
Ferric oxide is a solid, while SO2 and SO3 are gases.
5.003
train/chapter 1 112-151 (34).mp3
Decomposition of calcium carbonate to calcium oxide and carbon dioxide on heating is an important decomposition reaction used in various industries.
5.003
train/chapter 1 112-151 (4).mp3
Such a reaction in which a single product is formed from two or more reactants is known as a combination reaction.
5.003
train/chapter 1 112-151 (5).mp3
Do You Know?
5.003
train/chapter 1 112-151 (6).mp3
A solution of slaked lime produced by the reaction is used for white washing walls.
5.003
train/chapter 1 112-151 (7).mp3
Calcium hydroxide reacts slowly with the carbon dioxide in air to form a thin layer of calcium carbonate on the walls.
5.003
train/chapter 1 112-151 (8).mp3
Calcium carbonate is formed after two to three days of white washing and gives a shiny finish to the walls.
5.003
train/chapter 1 112-151 (9).mp3
It is interesting to note that the chemical formula for marble is also CaCO3.
5.003
train/chapter 1 146-151 (1).mp3
Calcium oxide is called lime or quick lime.
5.003
train/chapter 1 146-151 (2).mp3
It has many uses – one is in the manufacture of cement.
5.003
train/chapter 1 146-151 (3).mp3
When a decomposition reaction is carried out by heating, it is called thermal decomposition.
5.003
train/chapter 1 146-151 (4).mp3
Take about 2 g lead nitrate powder in a boiling tube.
5.003
train/chapter 1 146-151 (5).mp3
Hold the boiling tube with a pair of tongs and heat it over a flame.
5.003
train/chapter 1 146-151 (6).mp3
What do you observe?
5.003
train/chapter 1 152-197 (1).mp3
Note down the change, if any.
5.003
train/chapter 1 152-197 (10).mp3
Fill the mug with water such that the electrodes are immersed.
5.003
train/chapter 1 152-197 (11).mp3
Add a few drops of dilute sulphuric acid to the water.
5.003
train/chapter 1 152-197 (12).mp3
Take two test tubes filled with water and invert them over the two carbon electrodes.
5.003
train/chapter 1 152-197 (13).mp3
Switch on the current and leave the apparatus undisturbed for some time.
5.003
train/chapter 1 152-197 (14).mp3
You will observe the formation of bubbles at both the electrodes.
5.003
train/chapter 1 152-197 (15).mp3
These bubbles displace water in the Electrolysis of water test tubes.
5.003
train/chapter 1 152-197 (16).mp3
Is the volume of the gas collected the same in both the test tubes?
5.003
train/chapter 1 152-197 (17).mp3
Once the test tubes are filled with the respective gases, remove them carefully.
5.003
train/chapter 1 152-197 (18).mp3
Test these gases one by one by bringing a burning candle close to the mouth of the test tubes.
5.003
train/chapter 1 152-197 (19).mp3
CAUTION:
5.003
train/chapter 1 152-197 (2).mp3
You will observe the emission of brown fumes.
5.003
train/chapter 1 152-197 (20).mp3
This step must be performed carefully by the teacher.
5.003
train/chapter 1 152-197 (21).mp3
What happens in each case?
5.003
train/chapter 1 152-197 (22).mp3
Which gas is present in each test tube?
5.003
train/chapter 1 152-197 (23).mp3
Take about 2 g silver chloride in a china dish.
5.003
train/chapter 1 152-197 (24).mp3
What is its colour?
5.003
train/chapter 1 152-197 (25).mp3
Place this china dish in sunlight for some time.
5.003

No dataset card yet

Downloads last month
24