Chapter 4 Flashcards
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
Give example of cellular respiration
C6H12O6 (aq) (glucose) + 6 O2 (oxygen) = 6 H2O (water) + 6 CO2 (carbon dioxide) + 170kJ (energy)
What are the types of combustion and give a definition
Rapid: releases a great deal of energy within a short period of time
Spontaneous: fuel reaches its ignition temperature without any energy from outside source
Slow; occurs over a very long period of time
To create fire you need:
- Ignition source (flame or hot temp)
- Oxidizer (oxygen)
- Fuel (wood, gas, paper)
What is a precipitation reaction
Formation of an insoluble solid substance, “precipitate” when 2 solutions are combined.
Give example of precipitation
Vinegar and milk
What is acid base neutralization
Reacting of an acid with a base to form a salt and water
Generic formula: acid (aq) + base (aq) = salt (aq) + water (l)
Steps to do acid base neutralization
- Identify the acid and base
- Use cross over rule to write formula of the salt
- Balance equation
What is stoichiometry
Refers to relative quantities of moles in a balanced chemical equation
Neutralize NaOH and Back
Neutralize H2SO4 and RbOH
what is stoichiometry?
refers to the relative quantities of moles in a balanced chemical equation
What is exothermic
process that releases heat and light to the surroundings (becomes hot)
give an example of exothermic
combustion
explain the energy of exothermic reaction
broken bond energy is greater than energy needed for the newly formed bonds
what is endothermic
process where the reactions absorb energy from the surroundings (cools surroundings)giv
give an example of endothermic
recharging a battery
What is nuclear energy
The strong and weak nuclear forces exist within the nucleus of atoms and helps keep matter together.
Without these forces atoms would simply fall apart
What is nuclear stability
Refers to the state of a nucleus in which the nuclear force is greater than the forces of electrical repulsion between protons
What is radioactivity
Natural process in which an unstable atom spontaneously transforms into a more stable atom, or several more stable atoms, while releasing energy as radiation
What is nuclear fission
Nuclear reaction in which the nucleus of a large atom is split to form two or more lighter atomic nuclei
Nuclear fusion
Nuclear fusion in which two small atomic nuclei join together to form one heavier nucleus.
