Y11 Chemistry - Essentials and Science Inquiry Skills

Atom

The smallest unit matter can be divided into by chemical means.

Element

A substance made up of only one kind of atom

Compound

A substance made of two or more different elements chemically combined in a definite whole number ratio.

Molecule

A group of atoms held together by covalent bonds.

Mixture

A substance that contains two or more elements but is not chemically combined and lacks a definite ratio.

Heterogenous vs Homogenous Mixture

Heterogenous mixtures vary in composition throughout and may have clumps e.g. blood.

Homogenous mixtures are the same throughout e.g. air. Also known as solutions.

Pure Substances

Elements and Compound, which have a fixed and definite composition

Proton

A positively charged particle found in the nucleus of an atom

Neutron

A neutrally charged particle found in the nucleus of an atom

Electron

A negatively charged particle found in the electron cloud.

Isotope

Atoms of the same element that have the same number of protons/electrons but a different number of neutrons, as well as a different abundance, stability and mass

Atomic Number

The number of protons in an atom.

Mass Number

The number of Protons and Neutrons in an atom.

Ion

An atom with a positive (cation) or negative (anion) charge

Polyatomic Ions

Combinations of atoms that act as a single cluster with either a positive or negative charge e.g. Hydroxide

Relative Atomic mass

The weighted (by abundance) average of the masses of the isotopes of an element

Colavent Molecule

A combination of exclusively nonmetals e.g. H2O

Ionic Compound

A compound with an ionic bond between an anion and a cation.

Chemical Reaction

The process by which Reactants are replaced by products. The mass, number and type of atoms involved does not change, but their arrangement does.

Reactant

The substance present before a chemical reaction takes place.

Product

The substance present after a chemical reaction takes place.

Mole

6.02*10^23 particles of a substance. Used to describe the number of particles of a substance in a sample.

Avogadro's Number

6.02*10^23

Molar Mass

The mass of one mole of a substance, equal to the combined Relative Atomic mass of its constituents in Grams

Relative atomic mass is compared to 1/12 of the mass of this isotope

Carbon-12

Relative Molecular Mass

the sum of the relative atomic masses of the atoms in a molecule

Relative Formula Mass

the sum of the relative atomic masses of the atoms in an ionic compound

Basic Atomic model

Atoms have a tiny positively charged nucleus with protons (+1 charge) and neutrons (0 charge) that contains 99.97% of the mass of the atom. Most of the volume of the atom is empty space with a few electrons (-1 charge) flying around the nucleus.

Hypothesis

A prediction based on previous knowledge/evidence/observations. Often in the form of a cause and effect relationship between two variables.

Primary source

The originators of data and evidence, e.g. studies and research.

Secondary Source

Analysis and interpretation of primary sources e.g. textbooks, articles.

Validity

Whether an experiment is testing what it claims to be testing. Validity may be compromised if there are not sufficient controlled variables, however controlling for too many variables is also undesirable, to avoid the Mount Everest regression fallacy (mt. Everest is warm, controlling for altitude and location).

Reliability

The notion that an experiment repeated will have consistent results. Increasing your sample size, or doing multiple trials and then averaging your results should control for outliers, increasing the reliability of your findings.

Accuracy

The ability to reduce systematic error and obtain correct measurements

Precision

The ability to get consistent results, reducing random errors.

Uncertainty

The distance between your measurements and the true values of what you are measuring.

Systematic Error

A problem with your method or instruments that consistently produces an error in the same way, e.g. measuring the weight of a solution in a test tube and not subtracting the mass of the test tube.

Random Error

Unpredictable and typically small errors, e.g. using a stopwatch that may be unpredictably clicked a little before or after the measured event has occurred.

Independent Variable

The variable you change in an experiment

Dependent Variable

The variable you measure in an experiment

Controlled variables

Variables you keep constant during an experiment

Qualitative Variables

Variables that can be observed and categorised but not measured, e.g. material, colour, etc.

Quantitative Variables

Variables that can be measured such as mass, temperature and time. Split into discrete (can only be expressed as a whole number e.g. no. of protons) and continuous (can be expressed as a decimal e.g. mass)

Metals

Elements or alloys with high tensile strength, ductility, malleability, shiny lustre, high melting points, and thermal and electrical conductivity.

Polymers

A material made of smaller repeating units bonded together, including plastics, rubbers, cellulose, wool, silk, and paper.

Ceramics

Inorganic and nonmetallic solids that may contains metals, nonmetals, and metalloids held together by ionic and covalent bonds.

Composite material

A combination of ≥2 materials with different properties. The resultant material may have a range of properties inaccessible to its components. e.g. Reinforced concrete = steel (rebar) + concrete.