science for grade 8

1. Septina Restu N
8thGrade
ChemicalReactions
Exothermic and
endothermic
reactions

2. LessonObjective
Here’s what you’ll learn in this lesson:
1. Exothermic and endothermic reactions
2. Identify exothermic and endothermic reaction by
temperature change
3. Further word equations to describe reaction
4. Describe how science is applied across societies, industries,
and in research.

3. HOW CAN YOU TELL IF A
CHEMICAL REACTION HAS
TAKEN PLACE???

4. HOWCANYOUTELLIFA CHEMICAL
REACTIONHASTAKENPLACE???
COLORCHANGE
01

5. PRODUCE GAS
02
HOWCANYOUTELLIFA CHEMICAL
REACTIONHASTAKENPLACE???

6. PRODUCE
PRECIPITATE
03
HOWCANYOUTELLIFA CHEMICAL
REACTIONHASTAKENPLACE???

7. PRODUCE
ENERGY SUCH
AS LIGHT.
04
HOWCANYOUTELLIFA CHEMICAL
REACTIONHASTAKENPLACE???

8. TEMPERATURE
CHANGE
05
HOWCANYOUTELLIFA CHEMICAL
REACTIONHASTAKENPLACE???

9. TEMPERATURE
CHANGE
05
HOWCANYOUTELLIFA CHEMICAL
REACTIONHASTAKENPLACE???
Exothermic Reaction - heat is given off
(increase in temperature)
Endothermic Reaction - heat is absorbed
(decrease in temperature)

10. EXOTHERMICREACTION

11. EXOTHERMICREACTION
BURNING PROCESS
The exothermic reaction that is
most familiar to everyone is
combustion. When a flame
develops in this reaction,
combustion is called burning.
We say that a burning
substance is on fire

13. ENDOTHERMICREACTION
MELTING
Ice absorbs heat energy from the air and starts to melts.
SHERBET
Sherbet is a popular sweet, made from citric acid and sodium
hydrogencarbonate. When you put sherbet in your mouth, it feels cool.
Citric acid + sodium hydrogencarbonate  sodium citrate + carbon dioxide + water
COOKING

14. ENDOTHERMICREACTION

15. ENDOTHERMICREACTION

16. TEMPERATURE
CHANGE
05
Classify each of the following as
endothermic or exothermic.
 A log burning in the fireplace.
 A chemical ice pack
 Baking soda is added to vinegar causing the test tube to
become cold to the touch.
 A hand warmer
 Drain cleaner is added to a clogged pipe causing the
pipes to become warm.
 Photosynthesis
 Cellular respiration
 Baking a cake

17. Endothermic and Exothermic reaction

18. The initial and final temperature of two chemical reactions are shown
Reaction Initial temperature (oC) Final temperature (oC)
1 19 13
2 20 26
Explain which experiment 1 or 2 was endothermic and exothermic reaction!

19. In a beaker, solid ammonium chloride reacts
with solid barium hydroxide to produce barium
chloride, water and ammonia gas. In this
reaction, the temperature dropped from 25oC
to 12oC.
Determine whether the reaction is
endothermic or exothermic

20. Chemical
reactions
WORD EQUATION

21. What is a chemical reaction?
cooking rusting sticking
burning making metals living!
Can you think of any other chemical reactions?
Chemical reactions do not only happen in the laboratory.
Chemical reactions happen at anywhere that new substances are
made:

22. RUSTING PROCESS
IRON OXYGEN
WATER
VAPOUR
IRON
(III)
OXIDE
CHEMICAL EQUATION FOR RUSTING
Rusting
Iron
Fe + O2 + H2O → Fe2O3.H2O
WE CAN DESCRIBE THIS REACTION IN A CHEMICAL EQUATION

23. ChemicalEquation
Chemical equation is description of
chemical reaction that happened whether it
gave a changes like explosion, produce large
amount of gas, increasing of temperature, color
changes, or even no change that you can see.

24. ChemicalEquation
In chemical equation, the reactants (names
of substances that react) are given on the
left hand side and the products (names of
substances formed) are given on the right
hand side.

25. WORD
EQUATION
Typesofchemicalequations
SYMBOL
EQUATION

26. CHEMICAL
EQUATION
WORD
EQUATION
SYMBOL
EQUATION

27. IDENTIFYWHETHERAREACTANTORPRODUCT
Example:
When magnesium is burning in oxygen,
it will produce magnesium oxide
REACTANT:
MAGNESIUM and OXYGEN
PRODUCT:
MAGNESIUM OXIDE

28. CONSTRUCTAWORDEQUATION
Word Equation:
Reactants Products

29. CONSTRUCTAWORDEQUATION
Example:
When magnesium is burning in oxygen,
it will produce magnesium oxide
products
+ Oxygen Magnesium oxide
Word equation:
Magnesium
reactants

30. Convert this case below into word and symbol equation
When calcium hydroxide react with hydrochloric acid,
it will produce calcium chloride and water
Calcium hydroxide + Hydrochloric acid Calcium chloride + Water

31. TRYTHESE
QUESTIONS
02

32. 1. When a CHEMICAL reaction occurs, what is made?
A. No new substance is made
B. A new substance is made, but atoms are not created or
destroyed, they are just rearranged

33. 2. Which of the following is a list of some properties
that may be changed during a chemical reaction?
A. Shape, state (solid, liquid, gas), and colour
B. State, odour (smell), and shape
C. Odour, colour and state.

34. 3. What does this word equation represent?
Iron + oxygen  iron oxide
A. A physical change in iron (nothing new gets made)
B. A chemical reaction between iron and oxygen, where
rust (iron oxide) is produced (made)
C. A chemical reaction between iron and rust, where
oxygen is produced

35. 4. Magnesium (a grey metal) can be burned in air (oxygen) to produce
magnesium oxide (a white powder).
5. Sodium (a soft white metal) reacts with chlorine (a smelly gas used
to keep pool water clean) to produce sodium chloride (plain old table
salt!).
6. Iron (a grey metal) reacts with sulfur (a smelly yellow solid) to produce
iron sulfide (a black solid).
7. Lead is a grey metal. When it reacts with oxygen (a clear odourless
gas) a white powder lead oxide is produced.

36. 8. 0.048g of zinc was reacted with hydrochloric acid at room temperature.
Hydrogen gas and zinc(II)chloride are produced from this reaction
a. State the reactants from that reaction!
b. State the products from that reaction!
c. Write a word equation for that reaction taking place!