Chemical Reactions and Equations
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Questions and Answers

Which of the following is a characteristic of a chemical reaction?

  • Physical properties remain unchanged
  • It can be reversed easily
  • It is a temporary change
  • New products are formed (correct)

Physical changes result in the formation of new substances.

False (B)

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.

<p>insoluble</p> Signup and view all the answers

Match the following reactions with their respective types:

<p>2Mg + O2 → 2MgO = Combination Reaction Pb(NO3)2 + 2KI → 2KNO3 + PbI2 = Double Displacement Reaction Zinc + Sulphuric Acid = Single Displacement Reaction Candle Melting = Physical Change</p> Signup and view all the answers

What is formed when lead nitrate reacts with potassium iodide?

<p>Lead Iodide (A), Potassium Nitrate (B)</p> Signup and view all the answers

Rusting of iron is an example of a physical change.

<p>False (B)</p> Signup and view all the answers

Why should magnesium ribbons be cleaned before burning?

<p>To remove the oxide layer to ensure complete burning.</p> Signup and view all the answers

Flashcards

Chemical Reaction

A process where new substances with different properties are formed by rearranging atoms.

Double Displacement Reaction

A type of chemical reaction where two reactants exchange ions or groups of atoms, forming two new products. One of the products is usually an insoluble solid called a precipitate.

Combustion

A chemical reaction where a substance reacts with oxygen, producing heat and light, often forming an oxide.

Exothermic Reaction

A reaction that releases heat energy into the surrounding environment.

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Endothermic Reaction

A chemical reaction that requires heat energy to occur.

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Product

A substance that is formed during a chemical reaction.

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Reactant

A substance that participates in a chemical reaction.

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Precipitate

An insoluble solid that forms during a chemical reaction and settles out of the solution.

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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

  • A permanent change.

  • An irreversible reaction

  • New products are formed.

  • A change in the chemical composition of the compound.

  • Examples of chemical changes: Respiration, Digestion, growth of plants or animals, rusting of iron, etc.

  • Examples of physical changes: Melting of candle, cutting trees, boiling of water, etc.

  • 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) + Oâ‚‚(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.

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