The document discusses various topics relating to chemical reactions, including: 1) Chemical reaction indicators like color change, heat/light/sound production, gas formation, and precipitation. 2) The law of conservation of mass discovered by Antoine Lavoisier, which states that the total mass of reactants equals the total mass of products in a chemical reaction. 3) Different types of chemical reactions like decomposition, combination, precipitation, oxidation, and reduction reactions.

1. sscd.org.uk
Chemical Reactions
Sarah Jones

2. Chemical Reaction Indicators
• Colour change
• Evolution of heat, light or sound
• Gas produced
• Formation of a precipitate
www.fishfarmingedu.com.ng
A yellow precipitate of solid lead(II) iodide forms immediately when
solutions of lead(II) nitrate and potassium iodide are mixed.

3. http://www.unit5.org/chemistry/Equations.html

4. Law of Conservation of Mass
Antoine Lavoisier discovered the Law
of Conservation of Mass.
http://www.unit5.org/chemistry/Equations.html
http://en.wikipedia.org/wiki/Law_of_conservation_of_mass
The total mass of the reactants or
starting materials must be equal
to the mass of the products.

5. Chemical Equations

6. Meaning of Chemical Formula
http://www.unit5.org/chemistry/Equations.html

7. Showing States
(s) Solid (l) Liquid (g) Gas (aq) Aqueous
http://www.unit5.org/chemistry/Equations.html

8. http://www.unit5.org/chemistry/Equations.html

9. http://www.unit5.org/chemistry/Equations.html

10. http://en.wikipedia.org/wiki/Chemical_equation

11. http://www.unit5.org/chemistry/Equations.html

12. Visualising a Chemical Reaction
http://www.unit5.org/chemistry/Equations.html

13. http://www.unit5.org/chemistry/Equations.html

14. http://www.unit5.org/chemistry/Equations.html

15. http://www.unit5.org/chemistry/Equations.html

16. http://www.unit5.org/chemistry/Equations.html

17. http://www.unit5.org/chemistry/Equations.html

18. Classifying Chemical Reactions
http://wall.alphacoders.com

19. Decomposition Reactions
• When a single reactant breaks apart to form
several products.
XY  X + Y
• Soft drinks contain carbonic acid. This
decomposes to form water and carbon dioxide
gas.
http://www.mi9.com/

20. Thermal Decomposition
• When a substance will only decompose if
exposed to high temperatures.
• Thermal decomposition happen to sodium
azide when inflating vehicle airbags. When
heated it decomposes to form sodium metal
and nitrogen gas.
http://www.briggsauto.com/blog/airbag-system/

21. Combination Reactions
• When two reactants combine to form a single
product.
X + Y  XY
http://www.chemistryexplained.com
• These reactions are important in industry –
hydrogen gas + chlorine gas react to form
hydrogen chloride gas. This gas is then
bubbled through de-ionised water to produce
hydrochloric acid.

22. Precipitation Reactions
When two clear solutions are mixed together
and they form a solid e.g. scale (calcium
carbonate the builds up in a jug).
www.fishfarmingedu.com.ng
A yellow precipitate of solid lead(II) iodide forms immediately when
solutions of lead(II) nitrate and potassium iodide are mixed.

23. Oxidation Reactions
When a substance combines with oxygen during
a chemical reaction – combustion or corrosion.
http://en.wikipedia.org/wiki/File:Rust.rost.JPG

24. During combustion reactions substance burn
rapidly in oxygen and produce large amounts of
heat and light.
http://i.imgur.com/Qqma6Rl.jpg

25. Reduction Reactions
• When a compound loses oxygen atoms.
2CuO + C  2Cu + CO2
Copper (II) Oxide Carbon Copper Carbon Dioxide
• The copper oxide is reduced and the carbon is the
reducing agent. Also, the carbon is oxidised and
the copper (II) oxide is the oxidising agent.
• Oxidation and reduction occurs in pairs – Redox
Reactions.

26. • Redox reactions don’t always involve oxygen.
• Redox reactions include any reaction where
electrons are transferred from one substance
to another.
Oxidation is gain of oxygen or loss of electrons.
Reduction is loss of oxygen or gain of electrons.
Metal displacement reactions
are redox reactions.
http://catalog.flatworldknowledge.com

27. Activity Series
Shows the tendency for metals to react.
http://www.bbc.co.uk/bitesize/standard/chemistry/

28. When do reactions occur?
Chemical reactions occur only under certain
conditions e.g. iron will not rust without air and
water. This is why rusting does not occur on the
Moon.
www.travellerspoint.com

29. • You often need heat to cause a chemical
reaction e.g. to fry an egg, to get dough to
rise, a sparkler to burn etc.
• Sometimes you need electricity e.g. to charge
a car battery. The electricity produces
changes in the chemicals inside the battery.

30. Reaction Rate
• Some reactions are slow, like rusting, while
others occur quickly.
• Explosions are chemical reactions that occur
very quickly and produce large amounts of
heat, light and sound.
• The speed of a reaction is called its reaction
rate.

31. Controlling Reaction Rate
• Most reactions can be increased or decreased.
• Factors that affect reaction rate
– Temperature
– Concentration
– Surface Area
– Agitation
– Catalysts
www.chemistryexplained.com

32. Temperature
Increasing temperature normally increases
reactions rate.
– increase in particle speed - increased collisions.
The particles have more energy so when they
collide the chemical bonds are more likely to
break and easily form products.
http://catalog.flatworldknowledge.com/bookhub/4309?e=averill_1.0-ch14_s01

33. Lowering temperature can decrease reaction
rate.
– Refrigeration
http://www.appliancesonline.com.au

34. Concentration
• Concentration refers to the amount of
reactants present.
• Higher concentration = faster reaction
http://catalog.flatworldknowledge.com/bookhub/4309?e=averill_1.0-ch14_s01

35. Agitation
Stirring reactants can increase reaction rate.
http://en.wikipedia.org/wiki/File:Magnetic_Stirrer.JPG

36. Surface Area
Increasing surface area
means more particles are
reacting at the same
time.
http://catalog.flatworldknowledge.com/bookhub/4309?e=averill_1.0-ch14_s01
noosa.discountdrugstores.com.au

37. Catalysts
Chemicals that speed up reactions but are not
consumed during the reactions.
http://catalog.flatworldknowledge.com/bookhub/4309?e=averill_1.0-ch14_s01
A solution of hydrogen peroxide (H2O2)
decomposes in water so slowly that the
change is not noticeable (left). Iodide ion
acts as a catalyst for the decomposition
of H2O2, producing oxygen gas. The
solution turns brown because of the
reaction of H2O2 with I−, which
generates small amounts of I3
− (center).
The enzyme catalase is about 3 billion
times more effective than iodide as a
catalyst. Even in the presence of very
small amounts of enzyme, the
decomposition is vigorous (right).

38. Enzymes
• Enzymes are biological catalysts.
• The enzyme amylase is found in your saliva.
• Similar enzymes are secreted by you
pancreases and small intestine.
www.abpischools.org.uk