What’s it all about Alfie? Scientific tools and the scientific method Scientific tools and the scientific method What is chemistry? What is chemistry?

DEFINITIONS OF SCIENCE: Attempts at a one-sentence description Science is the search for the perfect means of attaining any end Science is the search for the perfect means of attaining any end The whole of science is after all nothing but a refinement of everyday thinking. The whole of science is after all nothing but a refinement of everyday thinking. Science is organized knowledge Science is organized knowledge Science is a method for the description, creation and understanding of human experience Science is a method for the description, creation and understanding of human experience Science is distinguished by testing ideas with measurements – the “scientific method” Science is distinguished by testing ideas with measurements – the “scientific method”

Tools of the trade Ways of dealing with information and thinking scientifically: Ways of dealing with information and thinking scientifically: Laws and Theories Laws and Theories HYPOTHESIS: an educated guess derived from various assumptions which can be tested using a range of methods; a proposition put forward for proof or discussion HYPOTHESIS: an educated guess derived from various assumptions which can be tested using a range of methods; a proposition put forward for proof or discussion

LAW A rule which describes specified natural phenomena within the limits of experimental observation (LDST) A rule which describes specified natural phenomena within the limits of experimental observation (LDST) Ohm’s Law, Gravity, Boyle’s Law… Scientific laws are precise, can be reduced to mathematical expressions Scientific laws are precise, can be reduced to mathematical expressions Laws have limited regions of application - don't always work in all situations Laws have limited regions of application - don't always work in all situations Laws do not provide understanding of why things happen Laws do not provide understanding of why things happen Laws cannot be extrapolated Laws cannot be extrapolated

THEORY Confirmed explanation of phenomena; a hypothesis tested and confirmed with facts (scientific evidence) not previously known (CCTD) Confirmed explanation of phenomena; a hypothesis tested and confirmed with facts (scientific evidence) not previously known (CCTD) A scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena; a hypothesis that has been confirmed or established by observation or experiment, and is accepted as accounting for the known facts (OED) A scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena; a hypothesis that has been confirmed or established by observation or experiment, and is accepted as accounting for the known facts (OED)

Features of theories Is a theory ever true? Is a theory ever true? o Difficult to say that a theory is true after some predictions are proved, because further predictions may be untrue. o New results may falsify the theory. o Theory of relativity demonstrated limitations in Newtonian mechanics. o Relativity is being challenged by new results. o Theories tend to be modified to improve their performance. Theories have predictive power Theories have predictive power o Prediction of existence of subatomic particles from quantum theory Theories provide understanding of why things happen Theories provide understanding of why things happen

Law and Theory contrasted using gases Boyle’s Law (17 th century) Boyle’s Law (17 th century) o Experimental observation of relationship between pressure and volume of a gas Kinetic theory of gases (19 th century) Kinetic theory of gases (19 th century) o Mathematical derivation of observed gas law using postulate that a gas consists of molecules which can be treated like small hard spheres in random motion. The behaviour of the gas is predicted using known mechanics of spheres

Scientific “method”

CHEMISTRY Chemistry is the science that describes matter: its properties, the changes it undergoes Chemistry is the science that describes matter: its properties, the changes it undergoes Important questions: Important questions: o How do substances combine to form others? o What are the energies involved o How are these substances made up in detail o What factors are involved in determining stability and so on o What is the make-up or composition of matter? o Why does matter have certain qualities? o Does matter undergo changes, and what kind? o Can it be produced from other types of matter? o What can we make with matter?

Chemistry as revelation or creation Much of science is about discovering and understanding the world Much of science is about discovering and understanding the world Another approach emphasizes creation: making new materials for improving our lot Another approach emphasizes creation: making new materials for improving our lot Synthetic chemistry has its roots in alchemy, which laid the foundation for modern science Synthetic chemistry has its roots in alchemy, which laid the foundation for modern science

Matter reveals itself through properties Salt and sugar are both white crystalline powders Salt and sugar are both white crystalline powders Both dissolve in water Both dissolve in water Solution of salt conducts electricity Solution of salt conducts electricity Solution of sugar does not Solution of sugar does not

Properties depend on the “mollycules” Salt is an electrolyte – contains ions Salt is an electrolyte – contains ions Sugar is made up of neutral molecules Sugar is made up of neutral molecules Molecules are not the smallest thing but are composed of atoms Molecules are not the smallest thing but are composed of atoms

Atoms or molecules? Stuff is ultimately made from atoms Stuff is ultimately made from atoms Ninety naturally occurring elements (only a fraction of those important) Ninety naturally occurring elements (only a fraction of those important) Atoms in combination make molecules Atoms in combination make molecules Millions of different substances Millions of different substances Molecules determine properties and behaviour Molecules determine properties and behaviour

Important themes Energy is a recurring theme in chemistry Energy is a recurring theme in chemistry Chemistry provides us with energy Chemistry provides us with energy Chemistry provides us with materials Chemistry provides us with materials Structure is function Structure is function Chemicals both natural and synthetic can be forces for good…and evil Chemicals both natural and synthetic can be forces for good…and evil