S3 - Chemistry Test (4) Flashcards
What is a fuel?
A compound which has stored energy
How do fuels release their stored energy?
By reacting with oxygen
What is a fuel reacting with oxygen referred to as?
Combustion / Oxidation
What are three different types of fuels?
- Petrol
- Diesel
- Glucose
- Charcoal
- Wax
- Wood
- Hydrogen
What is complete combustion?
When a fuel burns on a plentiful supply of oxygen
What are the products of complete combustion?
Water & Carbon dioxide
What is the equation for complete combustion?
Fuel + Oxygen ~> Water + Carbon dioxide
What are the three things required in order for a fire start?
Fuel, Oxygen & Heat
What is incomplete combustion?
When a fuel burns in a limited supply of oxygen.
What are the products of incomplete combustion?
Carbon monoxide, Soot, Water
What is the equation for incomplete combustion?
Fuel + Insufficient oxygen ~> Carbon monoxide + Soot + Water
What is crude oil?
A mixture of different hydrocarbons with different melting & boiling points
What is fractional distillation?
When hydrocarbon compounds are separated into different groups (fractions) due to them having different boiling points
What is a fraction?
A group of hydrocarbons with similar boiling points
What are hydrocarbons?
Substances made up of only Hydrogen and Carbon
Why do larger hydrocarbons have higher boiling points?
Because more energy is needed to break them down
Why are smaller hydrocarbons more flammable?
Because they evaporate easily and then mix with oxygen
Why do larger Hydrocarbons have a higher viscosity?
Because the molecules get tangled together
What is the general formula for alkanes?
CnH2n+2
What is the general formula for alkenes?
CnH2n
What is the general formula for cycloalkanes?
CnH2n
What are the prefixes used when talking about hydrocarbons and what numbers are they equal to?
Meth - 1
Eth - 2
Prop - 3
But - 4
Pent - 5
Hex - 6
Hept- 7
Oct - 8
What are all hydrocarbons?
- Insoluble
- Neutral pH
- Burn in a good supply of oxygen to produce carbon dioxide and water
What is a homologous series?
A family of compounds which fit a general formula and are chemically similar
What is the shortened structural formula for propane?
CH3 CH2 CH3
What are isomers?
Compounds which have the same molecular formula but have a different structural one
What do Alkenes contain that Alkanes do not?
A carbon to Carbon bond (C=C)
Alkenes are unsaturated due to them having…
a double bond
What is the shortened structural formula for butene?
CH2 CH CH2 CH3
What do fructose and glucose have in common?
They both have a single sugar unit
What do maltose and sucrose have in common?
They both have a double sugar unit
What is an example of a polysaccharide?
Starch
What is a polysaccharide?
A compound which has many sugar units
What are mono and di saccharides?
Compounds with one and 2 sugar units
What is the test for starch?
Iodine
What is the test for fructose, maltose or glucose?
Benedict’s solution
Which sugar can we not test for with iodone or benedict’s?
Sucrose
What is the word and chemical equation for photosynthesis?
Water + Carbon dioxide ~> Oxygen + Glucose
6H2O + 6CO2 ~> 6O2 + C6H12O6
Why is photosynthesis important?
- It lowers CO2 levels
- It supplies us with oxygen to breath
- It stores solar energy
How is starch formed?
- When a very large number of glucose molecules join together to form a giant molecule (polymer)
What is respiration?
- The opposite of photosynthesis
- When plants and animals get energy back out of glucose
What are cycloalkanes?
Isomers of Alkenes
What is an example of an effective solvent?
Ethanol
Alkanols have a … boiling and melting point than their corresponding alkanes and alkenes
higher
What compounds do alcohols produce when burned?
CO2 and H2O
What does dehydration do to an alcohol?
Removes the water and produces its corresponding alkene
Alcohols with hydroxyl attached to the end carbon will produce…
carboxylic acids
What are the properties of carboxylic acids?
- Taste and smell sour
- Soluble in water
- pH of less than 7
- They cause burns when undiluted
- They react with some metals
- They are neutralised by carbonates which causes fizzing
What is the general formula for alkanols?
CnH2n+1OH
What is the functional group for alcohols?
Hydroxyl group
What is the the functional group for alkanoic acids?
Carboxylic acids
What is the test for unsaturation?
Bromine Water
What do the following letters in the equation stand for?
Eh = c m Δ t
Eh - Energy released
c - Specific heat capacity
m - Mass of heated substance
Δt - Change in temperature
Why do larger molecules have higher boiling points?
Because of their stronger intermolecular forces
What is the general formula for alkanols?
CnH2n+1OH
What is the general formula for alkanoic acids
CnH2nO2