5. Language Of Chemistry Flashcards
Chemical reaction
a process in which a substance undergoes chemical change to form new substance(s) with new properties is known as a chemical reaction
Reactants
substances that take part in the chemical reaction
Products
substances formed after reaction is complete
What are the 4 characteristics of chemical reactions?
- Molecules of reactants come in close contact with each other
- bond between the atoms of the reactant molecules are broken
- atoms are rearranged by the formation of new bonds to form molecules of the products
- new atoms are neither created nor destroyed
Types of chemical reactions (6)
- Combination reaction
- Decomposition reaction
- Single Displacement reaction
- Double Displacement reaction
- Neutralisation reaction
- Combustion reaction
Combination reaction
where two or more reactants combine to form a single new product
Decomposition reaction
where a single reactant splits into its constituent elements or into other compounds
Single displacement reaction
where an element reacts with a compound and replaces the catio of that compound
Double displacement reaction
ions of two compounds exchange places in an aqueous solution to form two new compounds
Neutralization reaction
reaction between an acid and a base (they have opposite properties and the ability to cancel out/neutralize each other)
activation energy
the minimum energy required to start a reaction
Ionic compounds
- a compound formed by the oppositely charged ions with attract each other to form a chemical bond
9 conditions necessary for chemical reactions to occur
- close contact
- contact in solution (aqueous solutions)
- temperature
- light (photochemical reactions)
- concentration
- surface area
- electricity (electrochemical reactions)
- pressure
- catalyst
example of positive and negative catalyst
Positive catalysts (increases rate of reaction) - finely divided iron in Haber’s process
Negative catalyst (decreases rate of reaction) - phosphoric acid in decomposition of Hydrogen Peroxide
Aqueous solution
solution of a reactant in water
precipitate
an insoluble solid that emerges from a liquid solution in a chemical reaction
precipitation reaction
a reaction between two compounds in an aqueous solution state to give two new compounds, one of which in insoluble and precipitates out
what are characteristics of occurence of chemical reactions?
- evolution of gas
- change of color
- formation of a precipitate
- change in energy
- change of state
by what is evolution of gas indicated 3
effervescence (vigorous bubble formation)
colored fumes (No2 Gas is brown)
smell (hydrogen sulphide smells like rotten eggs)
effervescence
vigorous bubble formation in a liquid due to release of gas
how is hydrogen sulphide gas formed
ferrous sulphide (FeS) + Dil. Sulphuric acid
3 examples of change in color as a chemical reaction characteristic
- Grey Iron + RUST = reddish brown ferric oxide (layer formed)
- Blue Copper Sulphate becomes Green when iron is immersed (due to formation of ferrous sulphate)
- Green copper carbonate changes to black when heated (copper oxide)
2 examples of formation of precipitate
- As. of ferrous sulphate + As. sodium hydroxide = ferrous oxide (precipitate) - (DIRTY GREEN) + Sodium sulphate
- Lead acetate + Potassium iodide = Lead iodide (yellow precipitate) + Potassium acetate
what is the color of Ferrous oxide and Lead iodide
FeO - dirty green
Pbl2 - yellow
5 types of change in energy
- Evolution of light (Mg + O produces bright white light)
- Evolution/Absorption of heat ( exothermic/endothermic reactions)
- Evolution of Heat and Light (burning of coal)
- Evolution of sound (crackling noise like decripitation)
- Production of electricity (dry cells)
Endothermic & exothermic reaction
Endothermic - reaction where there is absorption of heat
Exothermic - reaction where there is a release of heat
1 example of endothermic and exothermic reaction
Endo - Hydrogen + Iodine = Hydrogen Iodide
Exo - Calcium Oxide (quicklime) + Water = Slaked lime (Calcium hydroxide)
Decrepitation
crackling noise produced by some chemical reactions (ex. firecrackers)
Example of production of electricity as change in energy
Dry cells/batteries used for domestic purposes contain chemicals that react to give electrical energy
word equation
when a chemical equation is represented using only the names of the chemicals involved, it is called a word equation
3 common acids
- hydrochloric acid (HCL)
- nitric acid (HNO3)
- Sulphuric acid (H2SO4)
3 common bases
Sodium Hydroxide (NaOh)
Potassium Hydroxide (KOH)
Ammonium Hydroxide (NH4OH)
chemical indicator
any substance that gives a visible sign, usually by color change, of the presence or absence of an acid or a base in a solution
3 examples of chemical indicators
Phenolphthalein
litmus
Methyl orange
basic property of litmus paper
turns red in acidic medium and turns blue in a basic medium
what happens if both red and blue litmus paper remain unchanged when put into a solution
the solution is neutral
from where is litmus paper obtained
certain lichens
