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

What is a suspension?

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

Alloys are a type of homogeneous mixture.

<p>True (A)</p> Signup and view all the answers

The process of burning a candle is a physical change.

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

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

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

Which of the following is a pure substance?

<p>Iron (A)</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 (A)</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 (D)</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

Flashcards

Pure Substance

A substance composed of only one type of particle, meaning all constituent particles are the same chemically.

Mixture

A combination of two or more substances that are not chemically bonded, and can be separated by physical means.

Homogeneous Mixture

A mixture where components are evenly distributed throughout, appearing as a single substance. Examples include saltwater and sugar dissolved in water.

Heterogeneous Mixture

A mixture where components are unevenly distributed, with distinct parts visible. Examples include sand and water, or oil and water.

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Solution

A homogeneous mixture where a solid (solute) is dissolved in a liquid (solvent). The solvent is generally present in a larger amount.

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Solute

The substance being dissolved in a solution (generally present in smaller amounts).

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Solvent

The substance that dissolves the solute in a solution (generally present in higher amounts).

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Saturated Solution

A solution containing the maximum amount of solute that can dissolve at a given temperature.

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Solubility

The amount of solute that can dissolve in a given amount of solvent at a specific temperature.

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Suspension

A mixture where a solid is dispersed throughout a liquid but does not dissolve. The particles are large enough to be seen with the naked eye.

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Colloid

A heterogeneous mixture where particles are evenly distributed throughout, but are larger than in solutions. They can scatter light.

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Tyndall Effect

The scattering of light by particles of a colloid, making the path of light visible.

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Dispersed Phase

The solid component of a colloid, dispersed throughout the dispersing medium.

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Dispersing Medium

The liquid, gas or solid that carries the dispersed phase in a colloid.

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Element

A pure substance that cannot be broken down into simpler substances by chemical reactions. Examples include gold, oxygen, and iron.

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Compound

A pure substance formed by the chemical combination of two or more elements in a fixed ratio. Examples include water (H2O) and salt (NaCl).

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Physical Change

The process of changing the physical state of a substance, like melting ice (solid to liquid) or boiling water (liquid to gas). No new substance is formed.

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Chemical Change

A chemical reaction where new substances with different properties are formed. Examples include burning wood (wood + oxygen --> ash + carbon dioxide + water).

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Filtration

The process of separating a solid from a liquid by pouring the liquid through a filter, leaving the solid behind.

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Residue

The solid material that remains on the filter paper after filtration.

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Filtrate

The liquid that passes through the filter paper during filtration.

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Alloy

A mixture of two or more metals, or a metal and a non-metal, created by melting and mixing the components.

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Concentration

A measure of how much solute is dissolved in a given amount of solvent. It can be expressed in different ways, such as mass by mass percentage.

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Mass by Mass Percentage

The ratio of the mass of solute to the mass of solution, expressed as a percentage.

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Centrifugation

The process of using a centrifuge to separate components of a mixture based on their density. Heavier components settle at the bottom.

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Liquid at Slightly Above Room Temperature

A substance that is normally solid at room temperature but melts slightly above it. Examples include gallium and cesium.

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Liquid at Room Temperature

A substance that is normally liquid at room temperature. Examples include mercury (the only metal that is liquid at room temperature) and bromine.

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Metalloids

Substances that have properties that fall between those of metals and non-metals. Examples include silicon, boron, and germanium.

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Metals

Substances that are typically shiny, malleable, ductile, and good conductors of heat and electricity. Examples include gold, iron, and copper.

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Non-metals

Substances that are typically dull, brittle, poor conductors of heat and electricity. Examples include oxygen, carbon, and sulphur.

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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 (Hâ‚‚O) 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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Chapter 2 Is Matter Around Us Pure? PDF

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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