PACKET #2 The Nature of Chemistry

Chemistry The study of the composition, structure, and properties of matter. Chemistry also studies the changes that matter undergoes.

Chemical Instruments used in chemistry, such as x-rays or electron microscopes, are used to identify chemicals.  Substance that is the same no matter where it is found.  More details to come later.

Chemicals II Where are chemicals found?  Everywhere  Toothpaste  Hair gel  Soap  Shaving cream  Shoes  Clothing  Hand sanitizer

Chemicals III How do you depend on chemicals on a daily basis?

Chemical Reactions Chemicals undergo change. These changes occur via chemical reactions.  Cooking food  Striking a match  Car engines  Running  Opening a soda bottle

Matter/Mass Chemical particles help make up matter and mass. The arrangement of these particles determine certain properties of the matter.  These are called physical properties.

Matter & Physical Properties

States of Matter Matter can be found in different states.  Solids  Liquids  Gases

Solids Has a fixed volume and shape Particles are held in a rigid state. There is little vibration

Liquids Has a fixed volume but no shape  Liquids assume the shape of whatever medium they are in. Particles are not held together very well.  The bonds, that hold the particles together, break apart easily Vibration of the particles is increased.

Gases Have no fixed volume and no fixed shape. Particles are weakly attracted to each other. Particles move and vibrate at high speeds.

Physical Changes of Matter

Physical changes are changes in which the identity of a substance does not change. They are about energy and states of matter. Example  When one steps on a can, and crushes it, a physical change occurs.  The shape of the object has changed  Melting ice cube  The shape of the object has changed  Energy has been added {heat} The molecules start to move faster and faster

Milk Before Milk After Physical Changes in Matter

Causes of Physical Changes One can use different types of force to cause a physical change  Motion  Temperature  Pressure

Small Physical Changes Melting a sugar cube  The substance is still sugar  Burning a sugar cube results in a chemical change

Chemical Properties

Chemical Change In a chemical change, the identity of the substance changes and a new substance is formed They happen on a much smaller scale.  Molecular level How is water identified?  H 2 O

Chemical Change II Some are changes are obvious.  There is a color change.  When Iron (Fe) rusts You can see it happen over a long period of time.  Burning of a sugar cube  The fire breaks bonds The sugar cube becomes blackened.

How are Chemical Changes Represented? Chemical changes are represented via a chemical reaction.  Sometimes, a series of chemical reactions must occur. Chemical reactions are represented by a chemical equation  Reactants  Products  Mercury (II) oxide  Mercury + Oxygen

Chemical Reactions There are two parts to a chemical reaction  Reactions  What the scientist puts in  Products  What the scientist gets out of the process

Evidence of Chemical Changes The formation of gas Formation of precipitate  When two clear solutions, when mixed together, become cloudy The release or absorption of energy  Change in temperature Change in color