Chapter 3: Matter

1. Chapter 3: Matter Properties and Change

2. States of matter • Solid: Particles are tightly packed and do not move. • Liquid: Particles are not rigidly held in place and are able to flow freely . • Gas: Particles are completely free to move. • Plasma: Plasma is ionized gas.

3. Physical Properties of Matter • A physical property of matter is a characteristic that can be observed or measured without changing the sample’s composition. • Extensive Properties: Depend on the amount of the substance being studied. • Intensive Properties: Do not depend on the amount of the substance being studied.

4. Chemical Properties of Matter • The ability of a substance to combine or change into one or more other substances is called a chemical property.

5. Changes in Matter • Physical changes: A change that alters a substance without changing its composition. • Example: Melting ice • Chemical change: A process that changes one substance in to another substance. Also called a chemical reaction.

6. Conservation of Mass • The law of conservation of mass states that matter cannot be created or destroyed. • In other words the mass of the reactants in a chemical reaction must be equal to the mass of the products.

7. Mixtures of Matter • A mixture is a combination of two or more pure substances. • A heterogeneous mixture is a mixture that does not blend smoothly throughout. • A homogeneous mixture is a mixture that does blend smoothly. • Homogeneous mixtures are also referred to as solutions.

8. Separating Mixtures • Filtration: Used to separate solids from liquids in heterogeneous mixtures • Distillation: Used to separate two liquids based on their boiling points. • Crystallization: Used to separate a pure solid from a liquid in a homogeneous mixture • Chromatography: Used to separate two liquids based on their ability to “stick” to the surface of a specific material.

9. Elements and Compounds • An element is a pure substance that cannot be separated into simpler substances by physical or chemical means. • Example: • Anything on the periodic table • A compound is made up of two or more different elements that are chemically combined.

10. The periodic table

11. More about compounds • The most important thing about compounds is that the elements that make them always combine in the same proportions. • This is called The law of definite proportions. • Percent mass:

12. Law of multiple proportions • The same two elements can combine in different proportions to create different compounds. • Example: H2O and H2O2

13. The atom • The atom is the smallest individual unit of a given element. • All matter is composed of atoms. • Atoms are composed of three subatomic particles: • Electrons • Protons • Neutrons

14. The electron

15. The Nucleus • The nucleus of an atom is comprised of protons and neutrons. • Protons are subatomic particles that have a charge of +1 and a mass of 1 amu. • Neutrons are subatomic particles that do not have a charge and a mass of 1 amu. • Rutherford Experiment:

16. How atoms differ • An atoms atomic number is the number of protons that it has. • Neutral forms of atoms have the same number of electrons as protons. • Mass number: • An atoms mass number is the sum of the atoms protons and neutrons. • Atoms with the same number of protons but different number of neutrons are called isotopes.

17. Electrons • Before we talk more about electrons we need to talk about light. • Visible light is a type of electro magnetic radiation. • EM radiation is both a particle and a wave.

22. Energy and atoms • Matter can only gain or lose energy in small, specific amounts called quanta. • A quantum is the minimum amount of energy that can be gained or lost by an atom.

23. The Photoelectric effect • When atoms gain enough energy they emit electrons at certain wave lengths and energy levels (quanta). • The equation to calculate the energy of a photon emitted is: • E = hv • Where h is planks constant and v is wavelength.

24. Atomic emission spectrum • The atomic emission spectrum of an element is the set of wavelengths of the electromagnetic waves emitted by atoms.

26. Energy states of hydrogen • The lowest allowable energy state of an atom is called its ground state • Danish physicist Niels Bohr proposed that electrons in atoms can only have certain allowable energy states. • As electrons gain energy they are promoted to higher energy states.

27. Quantum numbers and energy levels • Principle energy levels: • Principle energy levels are the major energy levels that electrons can occupy. • n = 1 • n = 2 • n = 3 • With in these principle levels there are sublevels • energy level one consists of one sublevel, energy level 2 consists of 2 sublevels, energy level 3 consists of 3 sublevels and so on…

28. Quantum theory and the atom

29. Principle energy levels • n = 1 • s • n = 2 • s • p • n = 3 • s • p • d • n = 4 • s • p • d • f

30. Ground State electron configurations • Low energy states are more stable that high every states. • Because of this atoms like to have their electrons in their ground states. • The aufbau principle states that each electron will occupy the lowest energy level available. • The pauli exclusion principle states that the maximum number of electrons that can occupy a single atomic orbital is two. • Hund’s rule states that single electrons with the same “Spin” must occupy each equal energy orbital before additional electrons can be added.

31. Electron configuration • Start by figuring out how many electrons and atom has. • Set up an electron configuration table. • Place electrons in orbitals one at a time before going to back to fill an orbital.

32. Write the ground-state electron configuration for the following elements. • Boron (B) • Strontium (Sr) • Antimony (Sb) • Rhenium (Re)