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Questions and Answers
Which of the following is a characteristic of a chemical reaction?
Which of the following is a characteristic of a chemical reaction?
Physical changes result in the formation of new substances.
Physical changes result in the formation of new substances.
False
What happens when magnesium burns in the air?
What happens when magnesium burns in the air?
It burns with dazzling white flames and forms magnesium oxide (MgO).
In a double displacement reaction, one of the products is usually _____ which precipitates out.
In a double displacement reaction, one of the products is usually _____ which precipitates out.
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Match the following reactions with their respective types:
Match the following reactions with their respective types:
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What is formed when lead nitrate reacts with potassium iodide?
What is formed when lead nitrate reacts with potassium iodide?
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Rusting of iron is an example of a physical change.
Rusting of iron is an example of a physical change.
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Why should magnesium ribbons be cleaned before burning?
Why should magnesium ribbons be cleaned before burning?
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Study Notes
Chemical Reactions and Equations
- A chemical reaction is a process where new substances with new properties are formed due to a rearrangement of atoms.
- Chemical reactions are either physical or chemical changes.
Physical Change
- A temporary change.
- A reversible reaction
- No new products formed.
- Changes in physical properties like color, shape, size, etc.
Chemical Change
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A permanent change.
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An irreversible reaction
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New products are formed.
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A change in the chemical composition of the compound.
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Examples of chemical changes: Respiration, Digestion, growth of plants or animals, rusting of iron, etc.
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Examples of physical changes: Melting of candle, cutting trees, boiling of water, etc.
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Activity 1.1: Burning of magnesium ribbon in air.
Activity 1.1: Burning of Magnesium Ribbon
- Cleaning a magnesium ribbon (3-4 cm) by rubbing with sand paper.
- To remove the oxide layer from the magnesium ribbon.
- Magnesium is a highly reactive metal.
Activity 1.2: Lead Nitrate Reacts with Potassium Iodide
- Observation: The magnesium ribbon burns with a dazzling white flame and forms a white powder (magnesium oxide).
- Reaction equation: 2Mg(s) + O₂(g) → 2MgO(s) (Amorphous Powder)
- Magnesium oxide is basic in nature.
Activity 1.3: Action of Sulphuric Acid on Zinc Granules
- Observation: Liberation of gas bubbles around the zinc granules.
- The gas evolved is hydrogen.
- Test for hydrogen: When a burning splinter is brought near to the gas, it burns with a pop sound.
Chemical Equations (General Information)
- Chemical equations represent reactions using symbols and formulas.
- They are a shorthand representation of chemical reactions.
Unbalanced Equations
- An unbalanced equation shows the reactants and products but the number of atoms on each side is not equal.
- It is also known as a skeletal equation.
Balanced Equations
- A balanced equation shows the reactants and products and the number of atoms of each element on both sides of the equation is the same.
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Description
Explore the fascinating world of chemical reactions and equations. This quiz covers the differences between physical and chemical changes, providing examples and definitions for a better understanding. Test your knowledge about the processes that lead to new substances and properties.
