Chapter 2: Is Matter Pure?
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Questions and Answers

What is meant by a substance?

A substance is a pure form of matter that has a fixed composition and specific properties.

List the points of difference between homogeneous and heterogeneous mixtures.

Homogeneous mixtures have a uniform composition and appearance throughout, meaning the components are evenly distributed. Heterogeneous mixtures have non-uniform composition with visibly distinct components.

What is a solution?

A solution is a type of homogeneous mixture formed when one or more substances (solutes) dissolve evenly in another substance (solvent).

Which of the following are examples of solutions?

<p>All of the above</p> Signup and view all the answers

What is a suspension?

<p>Both B and C</p> Signup and view all the answers

Alloys are a type of homogeneous mixture.

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

The process of burning a candle is a physical change.

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

The solubility of a substance generally increases as the temperature increases.

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

What are some examples of separation techniques used to separate mixtures?

<p>Common separation techniques include filtration, evaporation, distillation, magnetism, and chromatography.</p> Signup and view all the answers

A compound can be broken down into simpler substances by physical means.

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

Which of the following is a pure substance?

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

What are the steps involved in making tea?

<ol> <li>Boil water (solvent). 2. Add tea leaves (solute) to the boiling water and let it steep. 3. The tea leaves will dissolve in the water, creating a solution. 4. Strain the mixture to remove the tea leaves (insoluble), leaving behind the tea solution (filtrate).</li> </ol> Signup and view all the answers

The solubility of potassium nitrate in water decreases as temperature decreases.

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

What is the difference between a colloid and a suspension?

<p>Colloids have particles that are dispersed throughout the mixture but are too small to be seen with the naked eye. They also scatter light, exhibiting the Tyndall effect. Suspensions have larger particles that are visible to the naked eye and settle out over time. They also scatter light.</p> Signup and view all the answers

Which of the following is a homogeneous mixture?

<p>Sugar dissolved in water</p> Signup and view all the answers

How would you confirm that a colorless liquid given to you is pure water?

<p>You can confirm the purity of water by checking its boiling point (should be 100°C at standard pressure) and by testing for conductivity (pure water is a poor conductor of electricity). You can also perform a chemical test using litmus paper (pure water should be neutral).</p> Signup and view all the answers

Study Notes

Chapter 2: Is Matter Around Us Pure?

  • Matter can be judged as pure or a mixture.
  • Pure substances contain only one type of particle, with consistent properties.
  • Mixtures contain more than one pure substance.
  • Mixtures can be homogeneous (uniform composition) or heterogeneous (non-uniform composition).

2.1 What is a Mixture?

  • Mixtures are composed of more than one pure substance.
  • Mixtures can be separated by physical processes, like evaporation.
  • Examples of mixtures include seawater, soil, and air.

2.1.1 Types of Mixtures

  • Homogeneous mixtures (solutions) have uniform composition throughout.
  • Heterogeneous mixtures have non-uniform composition.
  • Examples of homogeneous mixtures are salt dissolved in water and sugar dissolved in water.

Activity

  • The activity involves creating different mixtures (e.g., copper sulfate in water) and observing uniformity.
  • Homogeneous mixtures are uniform in colour and texture.
  • Heterogeneous mixtures are non-uniform in colour and texture.

2.2 What is a Solution?

  • A solution is a homogeneous mixture of two or more substances.
  • Solutions can be solids, liquids, or gases.
  • The component present in larger quantity is the solvent.
  • The component dissolved is the solute.
  • Examples of solutions include sugar in water and air.

2.2.1 Concentration of a Solution

  • Dilute solutions have a small amount of solute.
  • Concentrated solutions have a large amount of solute.
  • Saturated solution is the maximum amount of solute that can dissolve at a given temperature.
  • Solubility is the amount of solute that can dissolve in a given amount of solvent at a specific temperature.

2.2.2 What is a Suspension?

  • Suspensions are heterogeneous mixtures where solid particles are dispersed in a liquid.
  • Particles in a suspension are visible and will settle out over time.
  • Suspension is easily separated by filtration.

2.2.3 What is a Colloidal Solution?

  • Colloids are heterogeneous mixtures.
  • Colloid particles are too small to see individually.
  • Colloids display the Tyndall effect (scattering of light).
  • Colloids are stable; particles do not settle out.

2.3 Physical and Chemical Changes

  • Physical changes do not alter composition (e.g., melting, dissolving).
  • Chemical changes alter composition (e.g., burning, rusting).

2.4 What are the Types of Pure Substances?

  • Pure substances are classified as elements or compounds based on their composition.

2.4.1 Elements

  • Elements are basic forms of matter.
  • Elements cannot be broken down into simpler substances by chemical reactions.
  • Examples include gold, iron, and oxygen

2.4.2 Compounds

  • Compounds are substances formed by the chemical combination of two or more elements.
  • Compounds have different properties compared to the elements from which they are made
  • Examples include water (H₂O) and salt (NaCl)

2.2 Mixtures and Compounds

  • Mixtures are physically combined substances with variable compositions and properties.
  • Compounds are chemically combined substances with fixed compositions and properties different from their component elements

Exercises

  • Included exercises for separation techniques, identifying solutions, classifying mixtures.

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Description

Explore the concepts of pure substances and mixtures in this quiz based on Chapter 2. You'll learn about the properties of matter, the distinctions between homogeneous and heterogeneous mixtures, and how mixtures can be separated. Test your understanding of these fundamental concepts in chemistry!

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