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Physical And Chemical Changes in One Shot | Cheat Sheet For Class 7th

PW Little Champs 6th, 7th & 8th・26 minutes read

Physical changes involve alterations in physical properties without forming new substances, are mostly reversible, and do not affect chemical properties. Chemical changes, like burning paper or rusting iron, result in the formation of new substances that are irreversible, showcasing distinct properties. The text emphasizes the differences between physical and chemical changes through various examples to aid in understanding these concepts better.

Insights

  • Changes in substances can be categorized into physical and chemical changes, with physical changes altering physical properties without forming new substances, while chemical changes involve the creation of new substances through chemical reactions.
  • The distinction between reversible and irreversible changes is crucial, with reversible changes like folding paper being temporary and not leading to new substance formation, while irreversible changes like burning paper result in permanent alterations and the formation of new substances, showcasing the transformative nature of chemical changes.

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Recent questions

  • What are physical changes?

    Changes in physical properties without new substances forming.

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Summary

00:00

Understanding Physical and Chemical Changes Simply

  • Introduction to physical and chemical changes in a cheat sheet series.
  • Exploring the concept of changes in substances, distinguishing between physical and chemical changes.
  • Emphasizing that changes occur due to reasons and are not automatic.
  • Discussing the types of changes: reversible and irreversible.
  • Differentiating between reversible changes (like folding paper) and irreversible changes (like tearing paper).
  • Explaining physical changes as alterations in physical properties without forming new substances.
  • Characteristics of physical changes include mostly being reversible and not involving new substance formation.
  • Describing physical changes as temporary and not affecting chemical properties.
  • Providing examples of physical changes like melting ice, boiling water, and breaking a chalk stick.
  • Introducing chemical changes as alterations in chemical properties, exemplified by burning paper.

13:57

Chemical Changes: Transforming Substances Permanently

  • Burning of paper results in a chemical change, forming a black substance.
  • Chemical changes involve the formation of new substances, irreversible in nature.
  • Transformation of flour into a cake exemplifies a chemical change, altering properties permanently.
  • Magnesium ribbon burning leads to the formation of magnesium oxide, showcasing a chemical reaction.
  • Mixing magnesium oxide with water produces magnesium hydroxide, illustrating further chemical changes.
  • Baking soda and vinegar reaction generates carbon dioxide bubbles, forming a new substance.
  • Lime water test confirms the presence of carbon dioxide through a milky effect, indicating a chemical change.
  • Copper sulphate solution reacts with iron, resulting in a displacement reaction and color change.
  • Rusting of iron due to oxygen and moisture forms iron oxide, a permanent chemical change.
  • Alloy creation involves mixing metals and non-metals to form new substances, like stainless steel.

27:36

Crystal Formation: Evaporation vs Crystallization

  • Salt crystals formed through evaporation do not have sharp edges like those of copper sulphate crystals, which are beautiful and distinct due to their formation through crystallization. While evaporation results in irregular shapes, crystallization produces well-defined structures that are more visually appealing and suitable for showcasing samples. This highlights the difference between physical and chemical changes, clarifying concepts for better understanding.
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