Food is cooked in order to...
- Improve the flavour and taste
- Improve the texture
- Make it easier to digest
- Kill microorganisms, to make it safe to eat.
Different ways to cook things are...
Did you know:
- Eggs are a good source of protein
- Potatoes are a good source of carbs
- Baking powder gives off CO2 when cooked
COOKING - Questions
1. What is the test for carbon dioxide?
Bubbling the unknown gas through limewater
2. What do the results show us?
If this causes the limewater to turn cloudy there is carbon dioxide present
3. Give four things tjhat could happen if a chemical change occours:
New substances are formed from old ones
There may be a change in mass
There is often a sunstantial energy change eg. rise or fall in temp.
The change cannot be reversed easily
All the materials that make up food are chemical. A material that is put in food to improve it in some way is called a food additive.
Additves are given as E numbers and can be seen on food labels. Ingredients are always listed in order of weight with the heaviest at the start.
Food additives can be used for many diferent things including...
- Improve Taste
- Mix ingritents
- Improve Appearence
The main types of food additives are...
- Food colours
- Flavour enhancers
FOOD ADDITIVES - Questions
1. What is active packaging?
Packaging that improves the quality of the product inside.
2. Give an example of active packaging:
A drink with a trigger for an endothermic reaction and therefore cools down the drink.
Smells are made of molecules witch travel up your nose and stimulate sense cells.
Esters are a common family of compounds used as perfumes. An Ester is made by reacting an alcohol with an organic acid. this makes an ester and water. This is the word equation:
ALCOHOL + ORGANIC ACID --------> ESTER + WATER
Nail varnish dissolves in ethyl ethanoate (nail varnish remover) but not in water. This is because the attraction between water molecules is stronger that that between water molecules and the particles in nail varnish. This means the attraction between the particles in nail varnish is stronger than the attraction between water molecules and particles in nail varnish.
SMELLS - Questions
Describe these words:
Soluble substances are substances that dissolve in a liquid e.g nail varnish is soluble in ethyl ethanoate
Insoluble Substances are substaces that do not dissolve in liquid e.g nail varnish is insoluble in water
A solvent is the liquid in whitch a substance is dissolved e.g ethyl ethonate is a solvent (an ester can be used as a solvent)
The solute is the substance that gets dissolved, e.g the nail varnish is a solute
A solution is what you get when you mix a solvent and a solute
MAKING CRUDE OIL USEFUL
What is Crude oil...
Crude oil is found trapped in permeable rock. When is extracted from the rock it is a thick, black and sticky liquid. Crude oil is a mixture of many hydrocarbons. It is used to produce a lot of useful products for e.g. Petrol and diesel oil.
Humans exploit natural sources of crude oil to make things like petrol and diesel oil. All the different hydrocarbons in crude oil have different boiling points. This means the oil can be separated into different fractions by heating, this is called Fractional distillation.
Cracking converts large alkane molecules into smaller alkene/alkane molecules. It breaks a bond and makes the one large alkane into two small alkene and alkane molecules.
MAKING CRUDE OIL USEFUL - Questions
1. State two pysical properties that differ between the refiner fraction and the bitumen fraction (i.e. the top product in the fractionating column and the bottom one)
a) Density b) Viscosity
2. If Propane (C2H8)is gas at room temp and Decane (C10H22) is liquid would you expect ocradecane (C18H38) to be a liquid or a gas at room temperature.
Liquid. This is because when there are more molecules the hydrocarbon is stronger so C2H8 would be very weak because there is only 8 molecules in the hydrocarbon.
Alkanes are hydrocarbons with only single covalent bonds. The name of an alkane always ends in - ane e.g. Methane (CH4), Ethane (C2H6), Propane (C3H8), Butane(C4H10).
Alkenes are hydrocarbons that have all single covalent bonds, all except for one double covalent bond between two adjacent carbon atoms. The name of an alkene always ends in - ene e.g Ethene (C2H4), Propene (C3H6), Butene (C4H8).
This is when Alkenes join together without producing another substance we call it polymerisation. This process requires high pressure and a catalyst.
MAKING POLYMERS - Questions
1. What are the formulas for alkanes and alkenes?
Alkene - CnH2n+2
Alkane - CnH2n
2. What is used to test for alkenes?
3. What do the results of the test above show?
if the bromine water turns colourless then there are alkenes present.
Polymers are plastics. They have many properties that make them useful. Different polymers have different properties witch results in them having different uses. for example, Nylon can be used for making outdoor clothing because its lightwieght, tough, waterproof, and able to block UV light.
Structure of plastics
Polymers (plastics) such as PVC consist of a tangeled mass of long chain molecules, in which molecules are held together by covalent bonds. Strong bonds means high melting points, weak bonds have low melting points.
Disposal of plastics
because of thier many uses we use plastics alot and therefore dispose of them alot. there are many ways of disposing of them but some have negitive impacts on the enviroment. e.g. Landfill sites :( not biodegradable, Burning :( greenhouse gases, Recycling :) not wasting.
DESIGNER POLYMERS - Questions
1. Name 3 properties of plastics
- (Use any of the following)
- Can be easily moulded Flexible Lightweight
- can be printed on un reactive non biodegradable
- can be coloured transparent Waterproof
- tough electrical and heat insulator
- 2. name four types of polymers
Polythene or poly(ethene), Polystyrene, Nylon, Polyester.
3. State a sutable polymer that can be used to make each of these:
fast - Food packaging Polythene Insulation Polystyrene
Wooden toys Nylon takeaway coffee cups Polystyrene
USING CARBON FUELS
Burning fuels (combustion)
When fuels burn, energy is released. this is called combustion. Many fuels are hydrocarbons. When fuels are burned they react with the oxygen in the air and produce oxides. when a hydrocarbon, like methane reacts with oxygen only carbon dioxide and water are made:
CH4 + 2O2 = CO2 + 2H2O
if a fuel burns without sufficient oxygen, e.g. in a room with poor ventilationor when a gas applience needs survicing, then incomplete combustion takes place and carbon monoxide (poisonous gas) can be formed. for example the incomplete combustion of methane:
- 2CH4 + 3O2 = 2CO + 4H2O
- Methane + oxygen = carbon monoxide + water
USING CARBON FUELS - Questions
1. The flame on your gas central heater boiler is burning with a yellow sooty flame. Explain what you should do and why?
You should get your heating checked out, because what is happening is incomplete combustion,This could cause an unhealthy amount of potentionaly fatal gas, carbon monoxide, to be produced.
2. why is complete combustion better than imcomplete combustion?
because complete combustion is safer, with incomplete combustion carbon monoxite builds up.
3. complete this word equasion
alcohol + ...................... = ester + ........................
Exothermic and Endothermic
Many reactions are accompinied to temperature rise. these are called exothermic reacions because heat is given out. Some reactions are accompanied by fall in temperature. These are called Endothermic reactions because heat is taken from the surrounndings.
breaking and making bonds
in a chemical reaction...
- breaking bonds is an endothermic reaction
- making bonds is an exothermic reaction
chemical reactions that require more energy to break than to make bonds are endothermic reaction. Chemical reactions that require more energy to make than to break bonds are exothermic reactions.
ENERGY - Questions
1. Name 4 things chemical reactions can be used for:
- Heat things
- Produce electrcity
- make sound
- Make light
2. how do you work out the energy change?
Energy supplied to raise energy = mass x specific heat capacity x temp change
Energy per gram = energy supplied / mass of fuel burned