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What changes are there?????????
Physical change
Chemical change
Physical change (e.g. chewing)
No new substance is formed
Properties of substances do not change
No heat/little heat is taken in or out
Chemical change (e.g. baking / cooking, chewing but with digestive juices)
New substances is formed
Properties of substances are different from reactants
Heat/light energy may be taken in or given outÂ
A+B (reactants) → C+D (products)
HOW do you know chemical reaction has taken place?
Colour change
heat/ light given off
Odour given off
Effervescence
Precipitate formed (solid forming in liquid)
Chemical changes occur due to…?
Interactions between different kinds of matter (mixing)
Interactions between matter and energy (heat, light, electricity)
Interactions between different kinds of matter (mixing)
Neutralisation
precipitation
Interactions between matter and energy (heat, light, electricity)
Combustion (heat)
Decomposition (heat, light electricity)
Electrolysis (electricity)
TYPES OF CHEMICAL REACTIONS
Involving acids and alkalis
Acids and alkalis chapter
Precipitation
Oxidation
Combustion
Decomposition
Other reactions in daily life
Precipitation
Salt solution + another salt solution
Salt solution + alkali
Process in which an insoluble solid (precipitate) is formed when two solutions are mixed
Oxidation
A substance may react with oxygen to form a new substance (substance is oxidized)
RustingÂ
Respiration
Combustion
The burning of substances in oxygen [basically every equation need oxygen] (heating required)
Energy is released usually in the form of heat and light
Combustion of magnesium
Combustion of coal
Combustion of sulfur
Combustion of hydrogen
Combustion of methane ( cow fart contains methane)
Decomposition
Process whereby a compound breaks down into two or more substances
Decomposition
Decomposition by light
Thermal decomposition
Electrolysis (using electricity to break down a compound)
Other reactions in daily life
Photosynthesis
Acid rain formation
Extra process:
Cooking
Decay of food
ElectroplatingÂ
Cooking
Denatured (break down bonds)
Coagulation (forming new structures)
Decay of food
Breaking down organic matter into simpler substances
Electroplating
Process of depositing a layer of metal on another substance using electrolysis
BENEFITS OF CHEMICAL CHANGES:
Releases nutrients back to earth
Manufacturing stuff like detergent and fertilisers
Metals are obtained
Synthesis of medicineÂ
Cooking
Electroplating
HARMFUL EFFECTS OF CHEMICAL CHANGES:
Rusting causes structures to corrode → unsafe
Decomposition leads to wastage of food and resources
Combustion release air pollutants (cars and factories)
Some air pollutants cause acid rain
SUMMARY: Chemical changes occur due to interactions between matter and/when:
Mixed
Heat
Light
electricity