presentation for Class 10 chapter Chemical reactions and equations

1. “Facts are not science — as
the dictionary is not
literature.”
Martin H. Fischer

2. Chemical Reactions
and Equations
Class 10 - SNEHA

3. Physical and chemical changes of
matter
● Milk is left at room temperature during
summers-
● An iron tawa/pan/nail is left exposed to
humid atmosphere.
● Melting of wax-
● Grapes get fermented.
● Food is cooked.
● Freezing of water to ice.
● Food gets digested in our body.
● We respire

4. Chemical change – one or more new
substances with new physical and
chemical properties are formed

5. Observations that help
determine a chemical reaction
A chemical reaction can be determined with the help of any of the
following observations:
a) Evolution of a gas
b) Change in temperature
c) Formation of a precipitate
d) Change in colour
e) Change of state

6. Physical change – change in colour or
state occurs but no new substance is
formed.
Example: Water changes to steam on boiling but no
new substance is formed (Even though steam and
water look different when they are made to react with
a piece of Na, they react the same way and give the
exact same products). This involves only a change in
state (liquid to vapour).

7. Similarly, the iron articles
undergoes physical changes
and develops a layer of rust
on its surface. It reacts with
the oxygen present in air and
moisture and develops rust
(hydrated iron (III) oxide).
These are all chemical reactions

8. Whenever a chemical reaction
takes place following changes
occurs
Change in colour
During rusting the iron articles
undergoes change in colour. We
have also observed that silver gets
tarnished when kept for a long time.
The metallic silver reacts with
hydrogen sulphide or sulphur
present in air and gets tarnished.
Chemical Reaction

9. On heating liquid changes its
state and converts to vapour
due to reaction within the
particles caused by heat.
Due to chemical reaction
food gets spoiled and smells
really bad.
Change in Odour
Change in State

10. Lime when mixed with water
undergoes certain physical
changes that makes it evolve heat
and give a clear solution. Such
reactions are called exothermic
reactions.
Change in Temperature
During Aerobic cellular
respiration in human body energy
molecules combines with inhaled
oxygen and releases energy
needed by the cells. It also
releases carbon dioxide gas and
water. Here is the overall equation
for aerobic cellular respiration:
Release of Gas

11. Chemical equation
Describing all of the chemical reactions that occurs around us in
words is quite impossible.
Like if you want to depict rusting of iron. Instead of writing the
phenomenon in sentences, you can simply write it as

12. This is known as word equation. And it itself describes the whole
phenomenon of rusting. Through this we can conclude that iron on
reacting with oxygen and water present in atmosphere undergoes
chemical transformation and gets converted to ferric oxide i.e. Rust.
○ In a word equation the reactants are always written on the left hand side
with plus sign in between the reactants.
○ The product is written on theright hand side.
○ In between reactants and products lies the arrow sign.
○ The arrow head points towards the direction of reaction.
○ You can also add the conditions and catalysts required to perform the
reaction above and below the arrow sign.

13. Balancing of a Chemical Reaction
Conservation of mass
According to the law of conservation of mass, no atoms can be
created or destroyed in a chemical reaction, so the number of
atoms for each element in the reactants side has to balance
the number of atoms that are present in the products side.
In other words, the total mass of the products formed in a
chemical reaction is equal to the total mass of the reactants
participated in a chemical reaction.

14. Balanced chemical equation
The chemical equation in which the
number of atoms of each element in the
reactants side is equal to that of the
products side is called a balanced
chemical equation.

15. Types of chemical
reactions
Taking into consideration different factors, chemical reactions are grouped into
multiple categories.
Few examples are:

16. ● Combination
● Decomposition
● Single Displacement
● Double displacement
● Redox
● Endothermic
● Exothermic
● Precipitation
● Neutralisation

18. Combination
reaction
In a combination reaction, two
elements or one element and one
compound or two compounds
combine to give one single
product.

19. Decomposition
reaction
A single reactant decomposes on
the application of heat or light or
electricity to give two or more
products.
Types of decomposition reactions:
a. Decomposition reactions which
require heat – thermolytic
decomposition or thermolysis.
○ Silver chloride turns grey in sunlight. This
is due to the decomposition of silver
chloride into silver and chlorine by light.

20. SLIDO Code -1188

21. ⓘ Start presenting to display the poll results on this slide.
When a magnesium ribbon is burnt in air, the
ash formed is

22. ⓘ Start presenting to display the poll results on this slide.
A change that lead to the formation of new
substances. These are called ___

23. ⓘ Start presenting to display the poll results on this slide.
In a physical change ..... are made

24. ⓘ Start presenting to display the poll results on this slide.
In a change where a new substance is made
and the change is difficult to reverse, that
change is:

25. ⓘ Start presenting to display the poll results on this slide.
Magnesium ribbon is rubbed before burning
because it has a coating of

26. ⓘ Start presenting to display the poll results on this slide.
Which of the following are exothermic
processes?(i) Reaction of water with quick
lime(ii) Dilution of an acid(iii) Evaporation
of water(iv) Sublimation of camphor
(crystals)

27. ⓘ Start presenting to display the poll results on this slide.
When Ag is exposed to air it gets a black
coating of

28. ⓘ Start presenting to display the poll results on this slide.
Pb + CuCl2 → PbCl2 + Cu
The above reaction is an example of:

29. ⓘ Start presenting to display the poll results on this slide.
In chemistry, an example of a physical
change is:

30. ⓘ Start presenting to display the poll results on this slide.
Reaction in which an element displaces
another element from its compound is called
…………. .

31. ⓘ Start presenting to display the poll results on this slide.
Write one physical change

32. ⓘ Start presenting to display the poll results on this slide.
Write one chemical change

33. ⓘ Start presenting to display the poll results on this slide.
One topic that i learned from today’s class

34. ⓘ Start presenting to display the poll results on this slide.
One topic that is not clear to me

35. “Eat well, sleep well and
Don’t read Science”
THANK YOU !