3.4 Notes Flashcards
Clues to a chemical reaction
Gas formation Solid formation( percipitate) Energy change Color and or smell change
Percipitate
When two liquid substances combine and make a cloudy substance
Chemical formula
Abbreviation that uses chemical symbols and numbers to represent a substance. Shows he many of each atom are present in a molecule of a substance
Subscript
Number written below and to the right if a chemicals symbol. A subscript can’t be hanged in a chemical formula
Can the subscript in a chemical formula change
No
Do chemical changes always involve a chemical reaction
Yes
Can physical changes have a chemical reaction
They can but not always
Examples of physical changes
Melting butter, boiling water, jello melting
Examples of chemical changes
Baking cupcakes
Flame
Burnt popcorn
Chemical reaction
Process by which one or more substances change to produce one or more different chemical and physical properties
Chemical formula
Shows how many of each know no of atom are present in a molecule of the substance
Subscript can’t be…..
Changed in a chemical formula. Don’t touch the subscript
What are subscripts
Number of atoms in each element of a molecule
What is the chemical names for the following covalent compounds
Co2
N2O
Carbon dioxide
Dinitride monoxide
Covalent and ionic: share or transfer
Covalent: share
Ionic: transfer
Covalent prefixes
Mono, di, tri, penta, hexa, hepta, octa, nona, deca, undeca, dodeca
Atoms are never ______ or ___________ in a chemical reaction
Lost or gained
Starting and ending substance
Starting: reactant
Ending: product
When balancing equations, what should always equal each other
Number of atoms in reactants= number of atoms in the products
Coefficient
Tells you how many molecules are needed
Remember how to do balancing equations
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Conservation of mass
Mass is neither created or destroyed. Has to be balanced in both sides of the equation
Law of conservation energy
Energy can’t be created or destroyed. Energy can be given off
Activation energy
Energy is needed for a reaction to occur
Examples of activation energy
Friction of a match allowing it to start burning
Exothermic reactions and example
Energy is given off
Ex: 2Na+Cl2–>2NaCl+energy
Energy is written in product
Know how to draw exothermic and endothermic reactions
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Endothermic reaction and example
Energy is absorbed
Ex:2H2O+ energy–> 2H2+O2
Energy is written in reactant side
Common exothermic and endothermic reactions examples
Exothermic:cellular respiration
Endothermic: photosynthesis
4 factors that affect chemical reaction rate and example
Temp: high temp=faster rate; low temp=slower rate
Surface area:greater surface area=faster rate; smaller area=slower rate
Concentration: high con= faster rate; low con= low rate
Catalysts and inhibitors: catalyst lowers activation energy needed so rate of reaction is faster; inhibitor slows down or stops reaction
Catalyst vs inhibitors
Catalyst: increases rate of reaction
Inhibitor: slows down or stops reaction
