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CHEMICAL INTERACTIONS. Chapter 1 - Chemical Reactions Outline/Review. 1.1 Matter and Its Changes. CHEMISTRY is the study of the properties of matter and how matter changes. An ELEMENT is a substance that cannot be broken down into any other substances by chemical or physical means.

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chemical interactions


Chapter 1 - Chemical Reactions


1 1 matter and its changes
1.1 Matter and Its Changes
  • CHEMISTRY is the study of the properties of matter and how matter changes.
  • An ELEMENT is a substance that cannot be broken down into any other substances by chemical or physical means.
  • All the matter around you is composed of one element or a combination of two or more elements.

A COMPOUND is a substance made of two or more elements chemically combined in a specific ratio.

  • An example of a compound is CO2
  • A MIXTURE is made from two or more elements or compounds in the same place but not forming new material.
  • A SOLUTION is a well-mixed mixture where substances are not easily seen.

Chemistry is the study of the kinds of and changes in matter.

  • A PHYSICAL CHANGE is when the form or appearance of a material changes.
  • An example of a physical change is water in the forms of ice, water, and water vapor.
  • A CHEMICAL CHANGE is when a new substance is produced.
  • An example of a chemical change is metal rusting.

The change of font type is an example of a physical change.

  • Changing whatsomething says is an example of a chemical change.
  • You can observe a chemical reaction by observing changes in the properties of matter.
  • A PRECIPITATE is a solid formed during a chemical reaction.

Some of the evidence for chemical reactions is:

  • production of a gas
  • precipitation of a solid
  • a change in temperature (either up or down)
  • a color change
  • change in physical properties

The smallest particle of an element is an ATOM.

  • A MOLECULE is the combination of two or more atoms.
  • An example of a molecule is H2O
  • An example of an atom is H
  • A CHEMICAL BOND is the force that holds atoms and molecules together.
  • Chemical reactions occur when chemical bonds are either formed or broken apart.
therefore to summarize
Therefore, to summarize . . .
  • Matter may be in the form of elements, compounds, or mixtures.
  • Chemical changes result in the formation of new substances.
  • Color change, production of a gas or a precipitate, a change in temperature, or a change in the properties of a substance are all clues that a chemical reaction has taken place.
  • Chemical reactions occur when chemical bonds are formed or broken
1 2 describing chemical reactions
1.2 Describing Chemical Reactions
  • A CHEMICAL EQUATION is a shorter, easier way to show chemical reactions.
  • Most elements are represented by a 1-2 letter symbol.
  • An example of a symbol is O for oxygen.
  • A compound is represented by a “word”, called a CHEMICAL FORMULA.
  • An example of a chemical formula is H2O.
  • A SUBSCRIPT shows the number of atoms of an element in a molecule.

The materials you have at the beginning of a reaction are the REACTANTS.

  • The materials you have at the end of a reaction are called the PRODUCTS.
  • A chemical equation uses symbols to show the reactants and products of a chemical reaction.
  • An example of a chemical reaction is:

H2 + O2 -----> H2O2

(H2 and O2 are the reactants while H2O2 is the product.)


All the atoms present at the start of a reaction are present at the end.

  • The law of conservation of mass states:

The amount of matter in a chemical reaction does not change, so the total mass of the reactants must equal the total mass of the products.

  • A balanced chemical equation has the same amount of atoms for the reactants and the products.
  • A COEFFEICIENT can be added to balance the number of atoms in an equation.

An example of a balanced equation is:

2 Mg + O2 -----> 2 MgO

  • Many reactions can be classified in one of three categories:

A SYNTHESIS reaction occurs when two or more substances combine to make a more complex compound.

  • An example of a synthesis reaction is:

2 SO2 + O2 + 2 H2O -----> 2 H2SO4

  • A DECOMPOSITION reaction breaks down compounds into simpler products.
  • An example of a decomposition reaction is:

2 H2O2 -----> 2 H2O + O2


A REPLACEMENT reaction is when one element replaces another in a compound OR when two elements trade places.

  • Examples of two replacement reactions are:

2 CuO + C -----> 2 Cu + CO2

MgCl2 + K2S -----> MgS + 2 KCl

therefore to summarize16
Therefore, to summarize . . .
  • A chemical equation uses symbols to show the reactants and products of a chemical reaction.
  • Matter is neither created nor destroyed during a chemical reaction.
  • Chemical reactions may be classified by the types of changes in reactants and products.
1 3 controlling chemical reactions
1.3 Controlling Chemical Reactions
  • Every chemical reaction involves a change of energy. Some reactions release energy and others absorb energy.
  • An EXOTHERMIC reaction releases energy in the form of heat.
  • An ENDOTHERMIC reaction absorbs energy and feels cold.
  • ACTIVATION ENERGY is the amount of energy needed to get a reaction started.

The rate of a reaction isaffected by such factors as concentration, surface area, and temperature.

  • Increasing the CONCENTRATION is one way to increase the rate of a reaction.
  • Increasing the SURFACE AREA is another way of speeding up a reaction.
  • Increasing the TEMPERATURE is a third way to speed up a reaction.
  • A CATALYST is a material that lowers the activation energy needed to start the reaction.

A type of biological catalyst is an ENZYME.

  • Enzymes provide a surface for the reactions to take place.
  • An INHIBITOR is a material used to slow down a reaction - often to make it less dangerous.
therefore to summarize20
Therefore, to summarize . . .
  • Every chemical reaction involves a change in energy. Some reactions absorb energy and others release it.
  • The rate of a chemical reaction can be controlled by such factors as concentration, surface area, temperature, and use of a catalyst or inhibitor.
1 4 fire and fire safety
1.4 Fire and Fire Safety
  • The rapid reaction between oxygen and a fuel is called COMBUSTION.
  • A FUEL is a material that releases energy when it burns.
  • Three things are necessary to start and maintain a fire--fuel, oxygen, and heat.
  • Water removes two parts of the fire triangle--heat and oxygen.

Some of the most common sources of fires are small heaters, kitchen fires, faulty electrical wiring, and carelessness with cigarettes (the most deadly).

  • Use baking soda to put out a fire that starts on the stove.
  • Try to extinguish small fires yourself, but leave a growing fire to the fire department.
  • Prevention is the best form of fire safety.
therefore to summarize23
Therefore, to summarize . . .
  • The fire triangle shows the three things necessary to start a fire and keep it burning: fuel, oxygen, and heat.
  • Water stops combustion by keeping the fuel from coming in contact with oxygen. Also, evaporation of water uses a great deal of heat and cools the fire.