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Is Matter Around us Pure Class 9 Science (Chemistry) - Midterm Marathon (Theory+Questions+Tips)

BYJU'S - Class 9 & 10・37 minutes read

The session focused on mastering the chapter "Date," covering substances, mixers, and solutions, emphasizing the importance of understanding and practicing concepts for exams. It discussed the classification of substances and mixers, the properties of solutions, saturated solutions, and physical versus chemical changes, highlighting the differences between elements, compounds, metals, non-metals, and metalloids.

Insights

  • The chapter "Date" in the Mission Mid Terms Yaar Marathon Series emphasizes understanding substances and mixtures, with a focus on homogeneous and heterogeneous mixers like alloys and fruit salad.
  • Solutions, a type of homogeneous mixer, involve dissolving substances like salt in water, with properties such as being homogeneous, having particles too small to be seen, and not exhibiting the Tyndall effect.

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Recent questions

  • What is the difference between substances and mixers?

    Substances consist of one type of particle, while mixers have more than one type of particle.

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Summary

00:00

Mastering "Date" Chapter: Concepts and Practice

  • The session is part of the Mission Mid Terms Yaar Marathon Series focusing on mastering a chapter called "Date."
  • The chapter covers concepts, questions, and key points for exams, emphasizing the importance of understanding and practicing.
  • The session involves revising concepts, practicing questions, and participating in a mentee quiz.
  • The chapter covers substances and mixers, discussing whole substances and mixers with examples like water and lemonade.
  • Whole substances consist of one type of particle, while mixers have more than one type of particle.
  • Mixers can be further classified as homogeneous or heterogeneous based on uniform composition and visible boundaries of separation.
  • Examples of homogeneous mixers include alloys like bronze and sugar water, while heterogeneous mixers include fruit salad and oil and water.
  • The classification of substances and mixers is crucial for understanding the chapter thoroughly.
  • The session encourages active participation and understanding of the concepts discussed.
  • The chapter delves into further classification, focusing on solutions as a type of homogeneous mixer.

18:50

"Understanding Solutions, Suspensions, and Colloids"

  • Mixers can be colored solutions or colloidal suspensions, with solutions being homogeneous and suspensions heterogeneous.
  • Solutions involve the dissolution of substances like salt in water, with the solvent being the medium in which the solute dissolves.
  • Components of a solution include the solute and solvent, with the solute being present in smaller amounts compared to the solvent.
  • Properties of solutions include being homogeneous, having particles too small to be seen, and not showing the Tyndall effect.
  • Saturated solutions contain the maximum amount of solute that can dissolve at a given temperature, while unsaturated solutions can dissolve more solute.
  • Supersaturated solutions have more solute than can normally dissolve, achieved by increasing temperature and then cooling.
  • Suspensions are heterogeneous mixtures where particles are suspended throughout the solvent, with larger particle sizes compared to solutions.
  • The Tyndall effect is always shown by colloids due to the scattering of light, distinguishing them from true solutions.
  • Colloids have particle sizes between solutions and suspensions, showing the Tyndall effect and being stable but requiring centrifugation for separation.
  • Physical changes, like melting chocolate or breaking wood, do not alter the chemical composition, while chemical changes, like burning a candle, result in new substances being formed.

40:46

Chemical and Physical Changes in Substances

  • Ammonium chloride is not a new substance and is an example of a physical change.
  • Chemical changes are usually irreversible and result in a change in chemical composition and properties.
  • Examples of chemical changes include burning paper, respiration, cooking, burning, and baking.
  • The burning of a candle involves physical changes when wax melts and chemical changes when new substances like carbon dioxide and water vapor are formed.
  • Elements consist of one kind of atom, while compounds are formed when elements chemically combine in fixed proportions.
  • Metals are malleable, ductile, lustrous, and good conductors of heat and electricity, while non-metals have opposite properties.
  • Metalloids are elements that exhibit properties of both metals and non-metals.
  • Mixtures are heterogeneous, while compounds are homogeneous and involve chemical combinations.
  • The separation of mixtures is easy, while the separation of compounds is difficult.
  • Emulsions are examples of colloids where liquid is dispersed in liquid, like milk in water.
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