The Nature of Matter - SNC1W

What is Chemistry?

  • Chemistry is the study of matter and the changes it undergoes.
  • Chemists investigate how and why different substances combine to create new ones and how substances interact with each other.
  • Chemistry plays a role in everyday life:
    • Cooking involves chemistry.
    • Medicine relies on chemistry.
    • Photography and crime-solving utilize chemistry.
  • Chemistry is sometimes referred to as the central science because understanding it is essential for fully grasping physics and biology.

What is Matter?

  • All things on Earth are composed of matter.
  • Matter can exist as a solid, liquid, or gas.
  • Matter is defined as anything that possesses mass and volume (occupies space).
  • All matter is made up of tiny particles called atoms, which are so small they require a microscope to be seen.
  • States of Matter
    • Solids: Atoms are tightly packed in a fixed shape.
    • Liquids: Atoms are close but can flow, resulting in no fixed shape.
    • Gases: Particles are widely spread and move freely at high speeds.
  • Solids
    • Maintain their shape unless a force is applied.
    • Do not flow or conform to their container's shape.
    • Examples: fur, tree stump, icicle
  • Liquids
    • Have no defined shape.
    • Take the shape of their container.
    • Examples: rain, lakes, oceans, orange juice, hot chocolate
  • Gases
    • Expand to fill the volume of their container, whether small or large.
    • Often invisible (e.g., air).
  • Understanding Matter
    • All matter has mass, which measures the amount of matter in an object.
    • Volume measures the amount of space an object occupies.
    • Solids, liquids, and gases fill volumes differently.
    • Examples: The CN Tower has a large volume, while coins have a small volume.
  • Atoms consist of protons, neutrons, and electrons.

Changing States

  • All matter can transition between solid, liquid, and gas states.
  • Extreme temperature changes may be necessary for a substance to change its state.
  • Phase Changes
    • Melting: Solid to liquid.
    • Freezing: Liquid to solid.
    • Evaporation: Liquid to gas.
    • Condensation: Gas to liquid.
    • Sublimation: Solid to gas.
    • Deposition: Gas to solid.

Particle Theory

  • Particle theory explains why matter behaves the way it does based on its particle composition.
  • Matter is anything with mass that takes up space.
  • Key points of particle theory include:
    1. All matter is composed of tiny particles.
    2. Particles are always in motion.
    3. There is space between particles.
    4. Adding heat increases particle movement.
    5. All particles in a pure substance are identical.
    6. Different substances have different particles.

Pure Substances and Mixtures

  • Matter can be classified as either a pure substance or a mixture.
  • Pure substances are either elements or compounds.
  • Mixtures are physically combined substances that can be separated into their original components.

Pure Substances

  • A pure substance contains only one type of particle throughout.
  • It can be either an element or a compound.
    • Element: A substance with a single kind of atom (e.g., Helium (He), Gold (Au), Sodium (Na), Carbon (C))
    • Compound: A substance made of two or more elements (e.g., Water (H_2O))
  • A compound consists of two or more elements (e.g., water, H_2O).
    • Water has two hydrogen atoms and one oxygen atom in each molecule.

Mixtures

  • A mixture contains more than one kind of particle.
  • It consists of two or more pure substances mixed together (e.g., coffee).
  • Mixtures can be solids, liquids, or gases.
    • Solid example: steel.
    • Liquid example: tea.
    • Gas example: air.
  • Heterogeneous Mixtures: Composition is not uniform; components are visibly distinct (also called mechanical mixtures).
    • Examples: mixed veggies, chocolate chip cookies, soil.
  • Homogeneous Mixtures: Composition is uniform throughout (also referred to as solutions).
    • Examples: orange juice, salt water.

The Scientific Method

  • The scientific method involves systematic observation, measurement, experiment, and formulating, testing, and modifying hypotheses.
  • Scientists use it to verify hypotheses through testing and experimentation.
  • The scientific method ensures reliable and valid results.
    • Reliability: Consistency of a measure; results are reproducible under the same conditions.
    • Validity: Accuracy of results; they represent what they are supposed to measure.
  • Steps of the Scientific Method
    1. Ask a question or make an observation.
    2. Create/Formulate a hypothesis.
    3. Test the hypothesis through experimentation.
    4. Draw conclusions.
    5. If the hypothesis is true- Communicate results.
    6. If the hypothesis is false or needs revision, repeat the process.

Laws of Matter

  • Law of Conservation of Mass: In a chemical reaction, the total mass of the reactants equals the total mass of the products.
  • Law of Definite Composition: Chemical compounds contain two or more pure substances, and compounds always have the same proportion of elements by mass (e.g., water is always 11% hydrogen and 89% oxygen).
  • Law of Multiple Proportions: When one element combines with another to form more than one compound, the ratio of the elements' masses in the compounds are simple whole numbers of each other.
    • Ratio of H to O in water compared to hydrogen peroxide is 1:2.

The Periodic Table of Elements

  • The periodic table displays all known elements, ordered by increasing atomic number and arranged based on their properties.
  • Elements form other substances.
  • Elements are represented by their element symbol (e.g., hydrogen is H).
  • Compounds are pure substances made of two or more different elements.
  • Metals are typically found on the left and center of the periodic table; they are dense, lustrous, malleable, have high melting points, and are great conductors of heat and electricity.
  • Nonmetals are dull, brittle, and conduct heat and electricity poorly.
  • Metalloids have properties of both metals and nonmetals.
  • The periodic table contains key information about each element:
    • Atomic name
    • Atomic symbol
    • Atomic number (number of protons)
    • Atomic mass
  • The periodic table is organized into groups (columns) and periods (rows).
  • Groups on the periodic table have similar physical and chemical properties.
  • Chemical Families
    • Alkali Metals:
      • Located in Group 1.
      • Extremely reactive and easily combine with other elements/compounds.
    • Alkaline Earth Metals:
      • Located in Group 2.
      • Very reactive (but less so than alkali metals).
      • Greyish-white color.
      • Very metallic and good conductors.
    • Noble Gases:
      • Located in Group 18.
      • Six noble gases in total.
      • Unique due to their full outer electron shell, making them stable.
    • Halogens:
      • Located in Group 17.
      • Contain six non-metallic elements.
      • Can be solid, liquid, or gas at room temperature.

Physical and Chemical Properties

  • Properties are characteristics used to describe how substances behave.
  • Properties can be physical or chemical.

Physical Properties

  • Can be observed without forming a new substance.
  • Can include quantitative (numerical data) and qualitative information.
  • Examples include color, viscosity, texture, luster, smell, state, melting point, boiling point, hardness, density, malleability, electric conductivity, solubility, ductility, heat conductivity.

Chemical Properties

  • Determined when a substance is changed and a new substance is produced.
  • Examples include flammability, ability to rust, reactivity, half-life, acidity, radioactivity, ability to oxidize, heat of combustion.

Solutes and Solvents

  • Solubility is a physical property.
    • A solute is the substance that is dissolved in a solution.
    • A solvent is the substance that does the dissolving.
  • A simple solution involves two substances mixed together uniformly, where the solute is dissolved in the solvent (e.g., Matcha powder in water).
  • According to particle theory:
    • Particles that are not attracted to each other will separate (e.g., oil and water).
    • Particles that are attracted to each other will bond (e.g., salt and water).

Saturation

  • Saturation occurs when no more of a substance can be absorbed or dissolved.
  • A solution is saturated when it contains the maximum amount of solute that can dissolve at a given temperature.
  • An unsaturated solution contains less solute than it can dissolve at a given temperature.
  • Increasing the temperature of the solvent increases its dissolving rate.
  • Stirred solutes dissolve more easily because particles are better distributed in the solvent.
  • Large solute particles are more difficult to dissolve.

The Universal Solvent

  • Water is the universal solvent because it can dissolve more substances than any other liquid.
  • Water is essential for living things because it can carry chemicals, minerals, and nutrients.
  • Common uses of water as a solvent include making tea/coffee, showering/using soap, gardening, and cleaning.
  • However, water cannot dissolve everything (e.g., oil).

Density

  • Density is the ratio of mass to volume for a substance.
  • Denser substances have particles closer together, resulting in greater mass per unit volume.
  • The formula for density is: Density = Mass / Volume
  • Sample Calculation:
    • A piece of aluminum has a volume of 20 cm^3 and a mass of 45g. What is its density?
    • Density = \frac{45g}{20cm^3} = 2.25 \frac{g}{cm^3}

Physical and Chemical Changes

  • Chemical properties are observed during a chemical change.
  • A chemical change transforms a chemical substance into one or more different substances.
  • A physical change alters a substance's physical properties, but this change is generally reversible (e.g., ice melting).

Bohr-Rutherford Diagrams

  • Bohr-Rutherford diagrams are atomic models showing the number of electrons in each shell of an atom.
  • The nucleus contains protons and neutrons.
  • The atomic number indicates the number of protons.
  • The number of neutrons can be found by subtracting the atomic number from the atomic mass.
  • Electrons orbit the nucleus in shells.
  • Each shell can hold a limited number of electrons:
    • Shell 1: 2 electrons
    • Shell 2: 8 electrons
    • Shell 3: 18 electrons
    • Shell 4: 32 electrons
  • Isotopes are forms of the same element with equal numbers of protons but different numbers of neutrons.

Elements and Compounds in Consumer Products

  • Electronic devices contain metals made from various elements and compounds (e.g., copper wiring, lithium batteries).
  • Other metals in electronics include lithium, tin, silver, gold, nickel, and aluminum.
  • E-waste can leach toxins into the environment, especially when improperly handled.
  • Burning e-waste is linked to respiratory and cardiovascular diseases.
  • Improper disposal of electronics releases harmful chemicals into the Earth, such as heavy metals that contaminate water and soils.
  • Electronic waste is a major source of toxic heavy metals in landfills.
  • Nitrogen, essential for plant growth, is added to soil via bacteria and human activities.
  • Excessive nitrogen from fertilizers can lead to overabundance of aquatic plants/algae, reducing dissolved oxygen and harming marine life; it can also contaminate water and restrict oxygen transport in the bloodstream.