chemical reaction
a process in which atoms of one or more substances rearrange to form one or more new substances
chemical equation
a description of a reaction using element symbols and chemical formulas
reactant
a starting substance in a chemical reaction
product
a substance produced by a chemical reaction
Law of Conservation of Mass
law that states that the total mass of the reactants before a chemical reaction is the same as the total mass of the products after the chemical reaction
coefficient
a number placed in front of an element symbol or chemical formula in an equation
endothermic
a chemical reaction that absorbs thermal energy
exothermic
a chemical reaction that releases thermal energy
activation energy
the minimum amount of energy needed to start a chemical reaction
catalyst
a substance that increases reaction rate by lowering the activation energy of a reaction
enzyme
a catalyst that speeds up chemical reactions in living cells
inhibitor
a substance that slows or even stops a chemical reaction
What are the two types of changes that matter can undergo?
Physical and Chemical
Characteristics of physical change
1) Does not produce a new substance
2) May have different physical properties
Name an example of a physical change
freezing water
Characteristics of chemical change
1) One or more substances change into a new substance
2) Different physical and chemical properties between starting and ending
Name an example of a chemical change
cupcake batter to a cupcake
chemical reaction
a process in which atoms of one or more substances rearrange to form one or more new substances
Indicators of a chemical reaction
color change, emission of odor, production of bubbles, temperature change, release of light, formation of a precipitate
True or False: Water boiling on a stove is a chemical change
False
True or False: Mix baking soda and vinegar
True
How do you tell if a chemical reaction has taken place?
If the starting and ending substances have different chemical properties, then a chemical reaction has occurred
Name the two types of substances.
1) elements
2) compounds
Substances have a fixed arrangement of ________.
atoms
What is the arrangement of water atoms?
2 hydrogen, 1 oxygen
chemical bond
an attraction between atoms when electrons are shared, transferred or pooled
What happens to atoms when the bonds are broken?
They can rearrange and form new bonds and new substances
What happens when you add electric energy to water?
The covalent bonds between the oxygen and hydrogen atoms will break and new bonds can be formed.
Did bubbles form on the copper wire from the last lab?
The electrical current broke the covalent bonds in the water and H2 and O2 gases were formed
chemical equation
a description of a reaction using element symbols and chemical formulas
diatomic molecule
elements that cannot exist in nature as a single atom
chemical formulas
represent compounds; use element symbols and subscripts to described the type and number
What is included in a chemical formula?
Both the reactants and the product are included
Who discovered the Law of Conservation of Mass?
Lavoisier
Are new atoms formed during conservation of mass?
No, atoms are rearranged
How do you balance equations?
Never change subscripts
Only change coefficient
Which side of the equation are reactants written on?
right
Which side of the equation is the product written on?
left