A force that holds two atoms together in a molecule.
What is a CHEMICAL REACTION?
a process in which one or more substances change to make one or more new substances.
For a chemical reaction to take place, what 2 things must occur to the bonds?
The old bonds must break and the new bonds must form.
Give EXAMPLES of chemical reactions
Autumn leaves and baking bread
Distinguish the properties of substances before and after a chemical reaction.
Products have new properties that are different from reactants.
What are the SIGNS of chemical reactions?
Gas formation, precipitate formation, color change, light, sound, heat, smell.
What is the sure sign that a chemical reaction to take place?
the formation of a new substance.
What must happen in order for a chemical reaction to take place?
original bonds must break and new bonds form.
What is a CHEMICAL FORMULA?
a shorthand way to use chemical symbols and numbers to represent a substance.
What is a SUBSCRIPT?
a number written below and to the right of a chemical symbol in a formula telling how many atoms are present. If there is no subscript then only one atom of that element is present.
What usually makes up a covalent bond?
2 nonmetals
What are the prefixes and meanings used in the names of covalent molecules?
mono 1, di 2, tri 3, tetra 4, penta 5, hexa 6, hepta 7, octa 8, nona 9, deca 10
What usually makes up an Ionic Compound?
A metal and a nonmetal
What's the trick for figuring out the checmical formula for a named Ionic Compound (like Berillium Chloride) ?
Overall charge must be neutral, so adjust the subscripts to cause the charge to be zero.
True of false: The names of Covalent Compounds can use prefixes whereas the names of Ionic Compounds do not.
True
What is a CHEMICAL EQUATION?
uses chemical symbols and formulas as a shortcut to describe a chemical reaction.
What are the REACTANTS?
the starting materials (left side)
What are the PRODUCTS?
the substances formed from the reaction (right side)
Who discovered the LAW OF CONSERVATION OF MASS?
Lavoisier (the total mass of the reactants is always equal to the total mass of the products).
What is the LAW OF CONSERVATION OF MASS?
mass is neither created or destroyed in ordinary chemical and physical changes.
How do you balance a checmical equation?
Count the atoms of each element in the reactants and in the products. Then add any coefficients to the reactants to represent this balance.
Describe a SYNTHESIS REACTION
a reaction in which two or more substances combine to form one new compound.
Describe a DECOMPOSITION REACTION
a reaction in which a single compound breaks down into two or more simpler substances (opposite of synthesis).
Describe a SINGLE DISPLACEMENT REACTION
a reaction in which one element or radical takes the place of another element or radical in a compound
Describe a DOUBLE DISPLACEMENT REACTION
a reaction in which a gas, a solid precipitate, or a molecular compound forms from the exchange of ions between two compounds “trade partners”
What is an EXOTHERMIC REACTION?
gives off energy (example: heat). Energy is released. Energy is a product. Right side.
What is an ENDOTHERMIC REACTION?
takes in energy (example: heat). Energy is required. Energy is written as a reactant. Left side.
What is the LAW OF CONSERVATION OF ENERGY?
A law that states that energy is neither created or destroyed, however energy can change form.
Who discovered is the LAW OF CONSERVATION OF ENERGY?
We didn't learn this.
What is a RATE OF REACTION?
speed at which new particles form.
A reaction can only take place if the __________ of the _________ collide with each other.
A reaction can only take place if the particles of the reactants collide with each other.
There must be enough _________ to break the bonds that hold the particles together.
There must be enough energy to break the bonds that hold the particles together.
What is ACTIVATION ENERGY?
the smallest amount of energy needed to start a chemical reaction.
What are SOURCES OF ACTIVATION ENERGY?
Friction, electric spark, light.
Name the factors that INCREASE THE RATES OF REACTION.
Temperature increase, high concentration, surface area increase, catalyst.
What is a factor that DECREASES THE RATE OF REACTIONS?
Inhibitors
Give two common examples of inhibitors
Preservatives in food, and some antibiotics.
What is a catalyst?
A substance that speeds up a reaction without being used up or changed very much.
Is a catalyst a reactant?
No, it's on the left-side but it is not a reactant since it doesn't change.
How does a catalyst speedup a reaction?
A catalyst lower the activation energy so the reaction happens more quickly.
Give two examples of a catalyst.
Enzymes in the body and the catalytic convertor in a car.
Describe an energy diagram?
A plot with Energy on the y-axis and time on the x-axis. It shows who the energy of a reaction changes with time.
What is the difference between an exothermic and endothermic energy diagram?
Exothermic: line starts in middle of y-axis, goes up, then down close to x-axis.
Endothermic: line starts close to x-axis, goes way up and then down to middle of y-axis.
What is an inhibitor?
a substance that slows down or stops a chemical reaction
What type of chemical reaction is this?
2 Na + Cl2 --> 2NaCl + energy
Exothermic since energy is given off.
What type of chemical reaction is this?
2H2O + energy --> 2H2 + O2
Endothermic reactin since energy is required.
Distinguish between a chemical symbol, a chemical formula and a chemical equation.
Symbol: H
Formula: H2O
Equation: 2H2O + energy --> 2H2 + O2
What is a percipitate?
A solid that is produced as a result of a chemical reaction in solution.
What type of reaction is: A + B --> AB ?
Synthesis reaction
What type of reaction is: AB --> A + B ?
Decomposition reaction
What type of reaction is: A + BC --> AC + B ?
Single Displacement reaction
What type of reaction is: AB + CD --> AC + BD ?
Double displacement reaction
Draw an exothermic reaction energy diagram and label the energy released and the activation energy.
activation energy (from start to top of diagram)
energy release (from start to bootom of diagram)
Draw an endothermic reaction energy diagram and label the energy absorbed and the activation energy.
Activation energy: from start to top of diagram.
Energy absorbed: from start to end of diagram.
S, D, SR or DR?
S8 + F2 --> SF8
S (Synthesis)
S, D, SR or DR?
HgO -- > Hg + O
D (Decomposition)
S, D, SR or DR?
HgO + Cl2 --> HgCl + O2
SR (Single Replacement)
S, D, SR or DR?
BaCl2 + Na2SO4 --> NaCl + BaSO4
DR (Double Displacement)
Balance: Ca + O2 ----> CaO
2Ca + O2 ----> 2CaO
Balance: N2 + H2 ---> NH3
N2 + 3H2 ---> 2NH3
Balance: Na + HCl ---> H2 + NaCl
2Na + 2HCl ---> H2 + 2NaCl
How many atoms are in 5H2
10
What is a coeffient in a chemical equation?
A number placed before a chemical symbol.
How many of each atom in 2Na2SO4
Na: 4
S: 2
O: 8
Balance: Mg + Cl2 --> MgCl2
Already balanced
To balance a chemical equation, you must add _________ in front of the chemical ________ in the equation.
To balance a chemical equation, you must add coefficents in front of the chemical symbols or formulas in the equation.
Give 3 descriptions of the law of conservation of mass
Mass can not be created or destroyed in ordinary chemical or physical changes.
The mass of the reactions will equal the mass of the products.
Atoms are not created or destroyed during a chemical reactrion.
Give the chemical formula for Dinitrogen Monoxide
N2O
Give the chemical formula for: Calcium Oxide
CaO
Give the chemical formula for Lithium Nitride
Li3N
Give the chemical formula for Potassium Sulfide
K2S
Balance: Al + O2 ---> Al2O3
4 Al + 3 O2 ---> 2 Al2O3
Give the chemical formula for Caesium Floride
CsF
What is a radical?
An ion made up of more than one atom. (ex: OH− ... Hydroxide)
