Matter and Its Properties

Matter

  • Definition: Anything that occupies space and has mass.

Learning Outcomes

  • Describe the main postulates of the kinetic theory of matter.
  • Explain the reason for the change of one state of matter to another and vice versa based on inter-particle space, inter-particle attraction, and collision.
  • Define and explain the law of conservation of mass using an example.

Examples of States of Matter

  • Solid: Examples include [Examples]
  • Liquid: Examples include [Examples]
  • Gas: Examples include [Examples]

Matching States of Matter

  • Solid: Molecules are packed together closely.
  • Liquid: Molecules can slide past each other.
  • Gas: Molecules can move around freely.

Introduction to Matter

  • Atoms: The smallest particle of matter that exhibits all its properties.
  • Atoms combine to form molecules.
  • Molecules: A group of atoms that shows all the properties of matter and can exist independently.

Kinetic Molecular Theory of Matter

  • Atoms and molecules in matter are in continuous motion.
    • Example: Ink spreading in water.
    • Example: Salt or sugar dissolving in water.
  • This continuous motion is known as the kinetic molecular theory of matter.

Main Postulates

  • All matter is composed of small particles (atoms or molecules).
  • Molecules of a substance are alike in all respects (shape, size, composition, and properties); molecules differ in different substances.
  • Molecules of a substance are in continuous and random motion, possessing kinetic energy; motion varies in different substances.
  • Molecules have spaces between them (intermolecular space).
  • Molecules are attracted to each other by an intermolecular force of attraction.

Intermolecular Force of Attraction

  • Depends upon:
    • Intermolecular space: Increase in space leads to a decrease in attraction and vice versa.
    • Nature of the Molecule:
      • Similar molecules exert a force of cohesion.
      • Solids: Maximum cohesion.
      • Liquids: Less cohesion.
      • Gases: Least cohesion.
      • Different molecules exert a force of adhesion.

Temperature and Kinetic Energy

  • Kinetic energy of a molecule increases with temperature and vice versa.
  • v^2 \propto T
  • mv^2
    • m = mass
    • v = velocity of molecules
    • T = temperature

Sci-Vocab

  • Kinetic Energy: Energy possessed by a body by virtue of its motion.

States of Matter

  • Three states: solid, liquid, and gas.
  • Division based on:
    • Intermolecular space
    • Intermolecular force of attraction
    • Kinetic molecular theory

Solids

  • Molecules are tightly packed.
  • Least intermolecular space.
  • Maximum intermolecular force of attraction.
  • Molecules vibrate about their mean positions.
  • Definite shape and volume.
  • Rigid and not easily compressed.
  • Least kinetic energy.

Liquids

  • Molecules are not very tightly packed; there is space between molecules.
  • Intermolecular force of attraction is not as strong as in solids.
  • Molecules can move freely.
  • More kinetic energy than solids.
  • Ability to flow.
  • No definite shape; takes the shape of the container.
  • Definite volume.

Gases

  • Molecules lie far away from each other.
  • Maximum intermolecular space.
  • Negligible intermolecular force of attraction.
  • Molecules move randomly in all directions.
  • High kinetic energy.
  • Molecules collide with each other and the container walls.
  • Occupy the entire space available.
  • Neither definite shape nor volume.

Change of State of Matter

  • Definition: The change of a substance from one physical state to another.
  • Depends upon:
    • Motion of molecules
    • Molecular forces
  • Decreasing intermolecular force increases intermolecular space, leading to a change of state.

Heating Solids

  • Molecules become energetic and vibrate vigorously.
  • Intermolecular space increases.
  • Molecules gain enough energy to overcome the force of attraction, converting the solid to a liquid.

Further Heating

  • Molecules become more mobile and leave the surface, converting the liquid to a vapor state.

Cooling

  • Kinetic energy of molecules decreases.
  • Intermolecular space decreases.
  • Intermolecular force of attraction increases.
  • The substance changes from gas to liquid to solid.

Prepping for PISA

  • Liquefaction: Process in which a substance changes from the gaseous state into its liquid state at a constant temperature.
  • Increasing pressure brings particles closer.

Process of Liquefaction

  • Applying pressure on a gas in a cylinder decreases the kinetic energy of particles.
  • Increases the force of attraction between particles.
  • Slows down the movement of particles.
  • The gas begins to compress.
  • Temperature reduces, removing enough energy to convert it into the liquid state.
  • Advantage: Compact transportation and storage.

Terms Related to Change of State

  • Melting: Solid to liquid at a fixed temperature (melting point).
  • Boiling: Liquid to vapor at a fixed temperature (boiling point).
  • Condensation: Vapor to liquid (condensation point).
  • Freezing: Liquid to solid on cooling (freezing point).
  • Sublimation: Solid directly to vapor without passing through the liquid state (occurs at all temperatures).
    • Examples: Iodine, camphor, and naphthalene.
  • Deposition: The reverse process where vapor converts directly to a solid.

Science Talk

  • How does a gas differ from vapor?

Science Alive

  • Naphthalene balls sublime and change into vapor state, keeping pests away.
  • Caution: Inhaling vapors can cause nerve and tissue damage.

Law of Conservation of Mass

  • Definition: Mass can neither be created nor destroyed.
  • The mass of the substance remains the same during the change.
  • The total mass remains conserved in any physical or chemical change.
  • Example: Melting an ice cube; the water will have the same mass as the ice cube.

Check Your Progress

  • The process of change of ice into water is melting.
  • The kinetic energy of molecules is maximum in gases.
  • The force exerted between the molecules of similar substances is called force of cohesion.
  • Iodine, camphor, and naphthalene show sublimation.

Activity: To Verify the Law of Conservation of Mass

  • Materials: Barium chloride (BaCl2) solution, sodium sulfate (Na2SO4) solution, conical flask, test tube, measuring cylinder, cork, weighing balance.
  • Procedure:
    • Take 10 mL of barium chloride solution in the conical flask.
    • Take 10 mL sodium sulfate solution in the test tube and keep it inside the conical flask carefully (do not mix).
    • Put the cork on the flask.
    • Measure the weight of the flask with its contents on a weighing balance and record it.
    • Tilt and swirl the flask to mix the two solutions. Sodium sulfate reacts with barium chloride to form a white precipitate of barium sulfate.
    • Measure the weight of the products formed.
  • Observation: The mass of the reactants before the reaction and the mass of the products formed after the reaction are equal.
  • Conclusion: The law of conservation of mass is verified.
  • Chemical equation:BaCl2(aq) + Na2SO4(aq) \rightarrow BaSO4(s) + 2NaCl(aq)

Matter

  • Made up of small particles (atoms or molecules).
  • Molecules of a substance are alike in shape, size, composition, and properties.
  • Molecules have spaces between them.
  • Molecules are attracted towards each other.
  • Kinetic energy is directly proportional to temperature.

Evaluation

  • The force of cohesion is maximum in solids.
  • Molecules of different kinds exert force of cohesion (FALSE).
  • The intermolecular space is maximum in gases.
  • Change of a substance from one physical state to another is known as change of state.
  • More the intermolecular force of attraction, less will be the intermolecular space.
  • Molecules can move very easily in solids (FALSE).
  • The kinetic energy increases with the increase in temperature (TRUE).
  • There can be gain or loss of mass in the case of change of state (FALSE).
  • A molecule exhibits all properties of matter (TRUE).
  • Molecules of a substance move in a fixed manner (FALSE).
  • The process of vapor converting to a solid is deposition.
  • The process of change of a liquid to vapor at a fixed temperature is boiling.
  • A group of atoms is molecules.

Higher Order Thinking Skills (HOTS)

  • Actions to increase the distance between the molecules of a gas stored in a closed container:
    • Pump some gas out of the container.
    • Increase the volume of the container.
  • The decreasing order of the kinetic energy possessed by the molecules of water in beakers at different temperatures is: S > P > R > Q (based on temperatures 50°C > 40°C > 35°C > 25°C).

Experiment: Law of Conservation of Mass

  • Materials: Vinegar, baking soda, two small paper cups, Sellotape, a weighing machine, a silicone food bag.
  • Procedure:
    • Fill one cup with vinegar and the other with baking soda.
    • Put both cups in the silicone bag (without spilling).
    • Find the mass of the cups, their contents, and the bag.
    • Seal the bag.
    • Pour vinegar into the cup containing baking soda without opening the bag.
    • Record the mass again. (The mass remains the same because the gas produced cannot escape.)

Integrate Physics

  • Collect samples of jelly, honey, and talcum powder. Determine their state (colloids).
  • Measure the weight of such substances using a weighing balance; unit: grams (g) or kilograms (kg).