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 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? H2O

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 gasFormation of precipitate

When two clear solutions, when mixed together, become cloudy

The release or absorption of energy Change in temperature

Change in color