Chemical Change:
- process that produces new substance (s)
- Particles of substance are broken apart
- Atoms are rearranged into new particles, forming a new substance
Types of Chemical Changes/ Reaction:
- Combination -> 2 or more elements combine to form a new product compound involving energy change
- Combustion-> a substance burns in oxygen to produce new product (s)
- Thermal (heat) Decomposition-> A compound breaks down into 2 or more smaller substances
- Precipitation -> 2 aqueous solutions are mixed to form one solid product (precipitate)
- Photosynthesis
- Respiration
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| How to define if its a chemical/ physical change |
INFORMATION ON WORD EQUEATION:
Burning
This is when a substance reacts with oxygen and produces a flame.
This is when a substance reacts with oxygen and produces a flame.
Burning always produces an OXIDE.
Burning an element produces ONE oxide.
Burning a compound produces TWO or more oxides.
The mass of the oxides formed will always be MORE than the mass of the substance being burned. (why?)
eg i. Burning magnesium
Burns with bright white flame to form magnesium oxide
Word equation: Magnesium + oxygen ----> magnesium oxide
Burning Methane (natural gas)
Methane is a COMPOUND of carbon and hydrogen. (ie a hydrocarbon. other hydrocarbons are wax, petrol)
It burns with a smoky flame to form carbon dioxide and water
Word equation: Methane + oxygen ------> carbon dioxide and water
Alcohol will also burn to form carbon dioxide and water.
This is when a compound splits apart and forms two (or more) new substances.. (Each of the new substances contains atoms that was there to start with)
note : Elements can NEVER decompose because they are only contain ONE kind of atom.
Each new substance formed will have LESS mass than the original substance
eg i. Heating copper sulphate
Copper sulphate DECOMPOSES and forms water vapour, leaving white anhydrous copper sulphate.
Word equation: Hydrated copper sulphate ----> anhydrous copper sulphate + water
NOTE: This reaction is reversible. If water is added to anhydrous copper sulphate then the solution turns blue again accompanied by a rise in temperature.
Heating copper carbonate The copper carbonate DECOMPOSES forming carbon dioxide gas and leaving copper oxide.
Word equation: Copper carbonate ----> copper oxide + carbon dioxide
iii. Heating limestone
The limestone decomposes and forms LIME and carbon dioxide gas
Word equation: Calcium carbonate -----> calcium oxide + carbon dioxide
or Limestone -----> lime + carbon dioxide
i Respiration
Respiration is the reaction that takes place in ALL living organisms that releases energy from sugar. This energy is used by the organisms for essentials like growth, movement and warmth
Respiration is the reaction that takes place in ALL living organisms that releases energy from sugar. This energy is used by the organisms for essentials like growth, movement and warmth
Word equation: Glucose + oxygen ----> carbon dioxide + water
ii Photosynthesis
This is the reaction that takes place in the chloroplasts (found mainly in leaves) of plant cells
This is the reaction that takes place in the chloroplasts (found mainly in leaves) of plant cells
It converts carbon dioxide and water into sugar and starch, using energy from the sun.
Word equation Carbon dioxide + water -----------> glucose + oxygen
(Chlorophyll+ sunlight)
(Chlorophyll+ sunlight)
Precipitation
e.g. lead (ll) nitrate + potassium iodide -> potassium nitrate + lead (II) iodide
Combination :
e.g. Potassium + chlorine gas -> Potassium chloride
JUST FOR LAUGHS :D
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