Chemistry Basics Quiz

Chemistry Grade 9 Revision

• Chemistry is the study of the composition, structure, properties, and changes of matter.
• Matter is anything that has mass and occupies a volume.
• Matter exists in four states: solid, liquid, gas, and plasma.

Organization of Matter

• Matter can be categorized as mixtures or pure substances.
• Mixtures can be homogeneous or heterogeneous.
• Pure substances can be elements or compounds.
• Elements are made of atoms.
• Atoms are made up of protons, neutrons, and electrons.

Definitions

• An atom is the smallest particle of an element that can exist and still show the properties of that element.
• An element is a pure substance that cannot be broken down into simpler substances by ordinary physical or chemical processes.
• A compound is a pure substance formed from two or more different types of elements chemically bonded together in fixed proportions, changing their properties.
• Molecules are groups of two or more atoms bonded together which can exist on their own. Molecules can be made of the same or different atoms.
• A formula unit represents the lowest ratio of ions in an ionic compound to give a neutral charge.

Atomic Structure

• Atoms have protons and neutrons in the nucleus.
• Electrons orbit the nucleus.
• Protons have a positive charge.
• Neutrons have no charge.
• Electrons have a negative charge.
• The atomic number (Z) of an element is the number of protons in its nucleus.
• All atoms of an element have the same atomic number.
• The mass number (A) of an element is the sum of protons and neutrons in its nucleus.
• The mass of an atom is primarily the mass of protons and neutrons in the nucleus.
• Electrons are found in orbitals around the nucleus.

Chemical Notation

• Chemical notation shows the mass number (A) and atomic number (Z) of an element.
• A = Z + N
• The mass number is written as a superscript and the atomic number is written as a subscript in front of the chemical symbol

Isotopes

• Isotopes are atoms of the same element that have the same number of protons and electrons but different numbers of neutrons.
• Number of neutrons = Atomic mass - Atomic number

Isotopes of Hydrogen

• Protium (¹H) has one proton and no neutrons
• Deuterium (²H) has one proton and one neutron
• Tritium (³H) has one proton and two neutrons

Matter and its states

• Matter has mass and occupies space.
• Mass is the amount of matter in an object.
• Volume is the amount of space an object occupies.
• Solids have a definite shape and volume.
• Liquids have a definite volume but take the shape of their container.
• Gases have neither a definite shape nor volume.
• Plasma is a highly energized state of matter.

Properties of Solids, Liquids, and Gases

• Solids have a rigid structure and high intermolecular forces.
• Liquids have a definite volume and can flow.
• Gases have low intermolecular forces and expand to fill their container.

Changes of States

• Melting is the change from solid to liquid.
• Freezing is the change from liquid to solid.
• Vaporization is the change from liquid to gas.
• Condensation is the change from gas to liquid.
• Sublimation is the change from solid to gas.
• Deposition is the change from gas to solid.

Boiling Point and Melting Point

• Boiling point is the temperature at which the vapor pressure of a liquid equals the surrounding pressure, causing the liquid to change into a vapor.
• Melting point is the temperature at which a substance changes from solid to liquid

Heating and Cooling Curves

• Heating and cooling curves show how temperature changes as heat is added or removed from a substance.

The Particle Theory

• The particle theory explains the behaviour of solids, liquids and gases.
• All matter is made of particles.
• All particles of the same substance are identical.
• Particles are in constant motion.
• There are spaces between particles.
• Particles have forces of attraction between each other.
• Temperature affects the speed of particles.

Diffusion & Osmosis

• Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.
• Osmosis is the net movement of water molecules from a region of high concentration to a region of lower concentration through a semi-permeable membrane.

Periodicity

• Periodicity is the recurrence of elements with similar properties at regular intervals in the periodic table.
• Elements are arranged according to their atomic number.
• The periodic table organizes elements according to their similar chemical properties and repeating properties.
• The arrangement of metals and nonmetals follows a pattern within the table.

Group I and II Metals

• Group I metals are called alkali metals.
• Group II metals are called alkaline earth metals.

Physical Properties of Group II Elements

• Atomic radius increases down the group, due to increasing electron shells.
• Ionisation energy decreases down the group, due to increased shielding and distance from the nucleus.

Chemical Properties of Group II Elements

• Group II metals react with oxygen and air, water, and dilute acids which lead to the formation of salt.

Physical Properties of Group VII - Halogens

• Halogens are nonmetals with low melting and boiling points.
• Halogens are more soluble in non-polar solvents than in polar solvents.
• Halogens can exist as gases, liquids or solids at room temperature.

Trends in Physical Properties

• Atomic radius increases down the group of elements.
• electronegativity decreases down the group of elements.
• Melting and boiling points increase down the group of elements.

Chemical Bonding

• Chemical bond is a lasting attraction between atoms, ions, or molecules.
• Valence electrons are involved in bonding.
• Ionic bonding involves transfer of electrons.
• Covalent bonding involves sharing of electrons.
• Metallic bonding involves valence electrons in a sea of electrons.

Lewis Dot Diagrams

• Lewis dot diagrams show the valence electrons of an element.
• These show bonding capabilities of the elements.

Deriving Chemical Formulas

• The method for deriving chemical formulas varies based on the type of compound (ionic or covalent).
• Ionic compounds create formulae according to the transfer of electrons to achieve a neutral charge.
• Covalent compounds use the valency, oxidation states or numbers in a compound.

Properties of Ionic Compounds

• Ionic compounds are crystalline solids at room temperature.
• They are hard and brittle.
• They have high melting and boiling points.
• They conduct electricity when molten or dissolved in water.
• They are often soluble in polar solvents like water.

Structure of lonic compounds

• Ionic compounds form crystal structures or lattices.
• The ions are arranged in a regular, repeating pattern.
• The ions are strongly attracted to each other via electrostatic forces.
• Ionic crystals are considered giant ionic structures composed of ions.

Properties of Simple Covalent Compounds

• Simple covalent compounds have low melting and boiling points.
• They are typically soluble in nonpolar solvents.
• They do not conduct electricity when molten.
• Simple covalent compounds are made up of molecules which are bonded together via weak intermolecular forces.

Intermolecular Forces

• Intermolecular forces are forces between individual molecules.
• These forces are weak compared to intramolecular forces.
• Two main types of intermolecular forces are Van der Waals forces and Hydrogen bonds.

Van der Waals Forces

• These are weak attractions between molecules.
• They arise due to uneven distribution of electrons.
• Instantaneous dipoles on one molecule can induce dipoles in neighbouring molecules.

Hydrogen Bonds

• Strong intermolecular forces formed when a hydrogen atom is covalently bonded to a highly electronegative atom.
• The hydrogen atom has a partial positive charge, which attracts an electron-rich atom in another molecule.

Structures of Simple Covalent Solids

• Solids containing discrete covalent molecules generally have lower melting and boiling points than giant ionic solids.
• Simple covalent solids, such as sulphur, phosphorus, iodine, water (ice) and carbon dioxide (dry ice), have weak intermolecular forces.

Allotropes

• Allotropes are different structural forms of the same element.
• Some elements, like carbon, can exist in multiple forms with different properties (e.g., diamond and graphite).

Giant Covalent Solids

• Giant covalent solids have high melting and boiling points.
• Covalent bonds extend throughout the structure.
• They are often insoluble in polar or nonpolar solvents

Allotropes of Carbon

• Diamond and graphite are allotropes of carbon.
• Their different structures lead to distinct properties.

Differences Between Diamond and Graphite

• Diamond is hard but graphite is soft and slippery.
• Diamond is a good conductor of heat while graphite is a conductor of both heat and electricity.
• Diamond is transparent, but graphite is opaque.

Additional Notes

• Various experiments demonstrate the principles of chemistry.
• The periodic table organizes elements in a way that lets us see repeating patterns.

Test your knowledge of atomic structure and the states of matter with this engaging quiz. Explore concepts like atomic numbers, isotopes, and the properties of different states. Perfect for students getting familiar with essential chemistry principles.