Chapter 4 Flashcards
(46 cards)
A physical change is..
Doesn’t change the nature or the characteristic properties of matter
Atoms and molecules of the substance do not change
What are the three states of physical change
- Dissolution
- Deformation
- Change of state
A chemical change is..
Changes the nature and characteristic properties of matter
The bonds between atoms are rearranged and new molecules are formed
What are the five signs of a chemical change
- Release of gas
- Emission or absorption of heat
- Emission of light
- A change in colour
- Formation of a precipitate
What does the law of conservation of mass state
- the total mass of reactants is always equal to the total mass of products
- this means that we cannot gain or lose matter in an equation. Both sides are equal
Suppose 111.7g of Fe metal rusts. We weigh the rust and find that the rust has a mass of 159.7g. What mass of oxygen reacted to the iron?
111.7g + x = 159.7g
Solve for x= 48g
Describe balancing a chemical equation
Is placing coefficients before each reactant and product so:
- atoms on the reactants side is equal to atoms on the product side
- equations have to be balanced because in reality chemical reactions cannot destroy atoms: only rearranging them.
How to balance equations
- You may introduce coefficients (big #s in front of formulas or atomic symbols)
- You cannot change or add subscripts
- For each element: total atoms on the left = total atoms in the right
Give an example of a balanced equation
CH4 + 2 O2 = CO2 + 2 H2O
How to balance a polyatomic
Keep polys together if they appear in the products and reactants. If they don’t, then you must balance the atoms individually.
Give an example
Of balanced poly
2 RbNO3 + 1 BeF2 = 1 Be(NO3)2 + 2 RbF
What are the four subscript brackets
Solid (s)
Liquid (l)
Gas (g)
Aqueous (aq)
What is aqueous
Meaning dissolved in water
What is a synthesis reaction
-formation of a complex molecule from atoms or simple molecules
-combination of 2 or more reactants to form a new product
- generic formula: A + B = AB
Example of synthesis reaction
N2 + 2 O2 = 2 NO2
Give formula for photosynthesis
6 CO2 + 6 H2O = C6H12O6 + 6 O2
What is a decomposition reaction
The transformation of complex molecules into simpler molecules or atoms.
Opposite of synthesis reaction
Generic formula; AB = A + B
Example of decomposition reaction
2H2O = 2 H2 + O*2
What is an oxidation reaction
-chemical change in which a metal reacts with oxygen
-most commonly known as the reaction that forms rust
-oxidation releases heat
Example of oxidation reaction
Metal + O2 = metalO2
What are other oxidation reactions
Combustion and cellular respiration
What is a combustion
Form of oxidation that releases a large amount of energy
Give an example of combustion
2 C4H10 (g) + 13 O2 (g)= 8 CO2 (g) + 10 H*2O + 5316 kJ (energy)
What is cellular respiration
Chemical change in which glucose and oxygen are used to generate energy. The reaction also produces co2 and H2O
