Matter

Matter: is anything that has mass and occupies space.

Mass : is the amount of material.

Mass : is what gives an object the properties of weight and inertia.

Weight : is a force and is due to the pull of

gravity on the object.

Inertia : resistance of an object to change its motion.

Matter that has uniform an unchanging composition is called a substance, also known as pure substance.

Pure substances are made of only one type of matter.

There are two types of pure substances: Elements and compounds.

The properties of matter can be:

Physical properties: density, color, odor, taste, shape, melting point, boiling point, etc.

Chemical properties: the ability of a substance to form rust, the ability of an element to combine chemically with other element, etc.

Extensive properties:

Depend on the amount of matter. Examples: mass, length,volume, etc..

Intensive properties:

Are independent of the amount of substance present.

Examples: demsity, melting point,boiling point, etc.

Physical Change: A change in the form of a substance, but not in its chemical composition; chemical bonds are not broken (or formed) in a physical change.

Examples: bend, grind, crumple, split, crush, melt, dissolve, cut, condense, evaporate, sublimate, freeze etc.

Chemical Change: The change of substances into other substances through a reorganization of atoms.

A chemical change is a process

that involves one or more substances changing into new substances.

A chemical change is refered as a chemical reaction.

Water is broken into hydrogen and oxygen.

Iron reacts with oxygen to form rust..

Sodium explodes when it reacts with water.

Some clues may indicate that a chemical change ( chemical reaction) is taking place

•Formation of a gas (bubbles)

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•Formation of a precipitate (solid formed)

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•Color change

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•Change in temperature

•Other forms of energy emitted

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•In general, the products have different properties

than the original substances.

The law of conservation of mass.

•Mass is neither created nor destroyed during chemical reaction.

Massreactants = Massproducts

Antoine Lavoisier (1743-1794), the father of modern chemistry, was the first to use the analytical balance to monitor chemical reactions. He explained the nature of combustion.

He also studied the thermal decomposition of mercury (II) oxide. Reactant à Products

Mercury (II) oxide à Mercury + oxygen

216g 200g ?

Ways to identify pure substances:

•By some properties like density, boiling or freezing points or others.

•Using the heating or cooling curves.

Pure substances increase gradually their temperature until the melting point is reached. The energy is used to increase the kenetic energy of the molecules.

Then the temperature remains constant during the whole melting process. The energy is used to overcome the forces that keep the particles together.

Only when all the solid has changed to liquid the temperature starts increasing gradually again (The energy is used to increase the kenetic energy of the particles) until the boiling point is reached.

Then the temperature remains constant during the whole boiling process (The energy is used to overcome the forces to separate the particles even more).

Only when all the liquid has changed to gas the temperature starts increasing again (Once more, the energy is used to increase the kenetic energy of the particles) .

Boiling point: Temperature at which a liquid changes to gas.

Melting point: Temperature at which a solid changes to liquid.

Freezing point: Temperature at which a liquid changes to solid.

Occur at the same temperature:

Freezing and Melting

Boiling and Condensation

Note: Evaporation occurs at any temperature while boiling occurs at the boiling point.

Mixtures, on the other hand, keep increasing the temperature even during the boiling process.

The boiling and melting points of a mixture change respect to the pure substance.

For example a water solution will have higher boiling point and lower melting point than pure water.

Mixture:

matter that can be separeted physically into components parts.

They are made of two or more pure substances in which each pure substance retains its indivudual chemical properties..

Examples: muddy water, tap water, salt dissolved in water, sand and water, sulfur and iron....

Some methods to separate the components of a mixture are:

•Precipitation

•Decantation

•Filtration

•Distillation

•Chromatography

•Crystallization

Homogeneous mixtures : is a mixture in which the components are evenly distributed among each other. You can’t see the component parts.

Homo means the same throughout.

It has a constant composition throughout.

Homogenous mixtures are also called SOLUTIONS

Examples: Salt dissolved in water, sugar dissolved in water, apple juice, tea, copper (II) sulfate solution in water, alloys....

http://www.chem.ufl.edu/~chm2040/Notes/Chapter_1/substances.html

Heterogeneous mixture : the components are not evenly distributed among each other. An heterogeneous mixture has two or more distinct phases that are usually detectable. This type of mixture does NOT have uniform properties.

Hetero means:Regions have different properties

Heterogeneous mixtures that look like solutions can be distinguished because they scatter light (Tyndall effect).

Examples: Sand water, oil and water, milk, sulfur and iron, granite, blood...

http://www.chem.ufl.edu/~chm2040/Notes/Chapter_1/substances.html

Water Solutions are transparent. You can see through them.

The mixture remains stable and does not separate after standing for any period of time.

The particles are so small they cannot be separated by normal filtration.

A solution may have a "color" but it will still be transparent.

•Colloids are mixtures with particle sizes that consist of clumps of molecules. The particles have dimensions between 2 to 1000 nanometers.

•The colloid looks homogeneous to the naked eye. Fog and milk are examples of colloids.

•Colloids frequently appear "murky" or "opaque".

• The particles are large enough to scatter light. You have experience with the way fog interacts with the light from car headlights. •Colloids generally do not separate on standing. They are not separated by filtration

•Suspensions are mixtures with particles that have diameters greater than 1000 nm, 0.000001 meter.

•The size of the particles is great enough so they are visible to the naked eye. Blood and aerosol sprays are examples

•Suspensions are "murky" or "opaque".

•They do not transmit light.

•Suspensions separate on standing.

• The mixture of particles can be separated by filtration.

Pure substances are made of only one type of matter. There are two types of pure substances: elements and compounds.

Element:

•A pure substance that cannot be separated into simpler substances by physical or chemical means.

•An elements is composed of a single type of atom

•All the elements are included in the periodic table.

Examples: Calcium (Ca), Sodium (Na), Chlorine (Cl2)...

There are 91 naturally occurring elements and several synthetic

Compounds : pure substances made of more than one type of atom.

A compound is the combination of 2 or more elements, combined chemically.

Compounds can be broken into two or more elements by chemical means.

Examples: Water (H2O), sodium chloride (common salt:NaCl)

Carbon dioxide (CO2), ethanol (CH3CH2OH)...

There are approximately 10 million known compounds

•Compound can be broken down into simple substances by chemical means.

•To separate a compound into its elements oftten requires external energy such as heat or electricity.

•Electrolysis is a process that uses electric energy to break a compound into its elements.

Water (H₂O) can be broken down into Hydrogen (H₂) and Oxygen

(O₂) through electrolysis.

Law of definite proportions:

•The elements that form a compound combine in

definite proportion by mass.

• Percent by mass (%) = mass of element x 100

mass of compound

When different compounds are formed by the combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole number.

Example

• 4.00g of H and 32.0g of O form 36.0g of H₂O

• 2.00g of H and 32.0g of O form 34.0g of H₂O₂

• The ratio H in water to H in hydrogen peroxide that combines with 32.0g of oxygen in each compound is

4:2 or 2:1

Energy: The ability to cause changes in matter

Law of conservation of energy: There is no loss or gain of energy. Energy changes from one form to another.

During nuclear reactions matter can change into energy and viceversa: E=mc²