Science [2 Mark Questions]

Sodium metal test: Add a small piece of sodium metal to the organic liquid (to be tested), taken in a dry test tube. If bubbles (or effervescence) of hydrogen gas are produced, it indicates that the given organic liquid is an alcohol.

1. All the members of the homologous series can be represented by the same general formula.
2. Any two adjacent homologues differ by 1 carbon atom and 2 hydrogen atoms in their molecular formulae.

Due to the presence of free electrons in a graphite crystal, it conducts electricity however; a diamond crystal does not have free electrons so it does not conduct electricity.

Uses of ethanol:

1. It is used in the manufacture of paints, varnishes, lacquers, medicines, perfumes, dyes, soaps and synthetic rubber.
2. It is used as a solvent. Many organic compounds which are insoluble in water are soluble in ethyl alcohol.

A detergent is the sodium salt of long chain benzene sulphonic acid which has cleansing properties in water.
Example: Sodium n-dodecyl benzene sulphonate.

Carbon forms a large number of carbon compounds because carbon atoms can link with one another by means of covalent bonds to form long chains of carbon atoms.

When soap is used for washing clothes with hard water, a large amount of soap in water is reacting with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum, before it can be used for the real purpose of washing.

Common salt is added to the mixture to make the soap come out of solution. Though most of the soap separates out on its own but some of it remains in solution. Common salt is added to precipitate out all the soap from the aqueous solution.

Diamond has a high melting point because a lot of heat energy is required to break the network of strong covalent bonds in the diamond crystal.

1. Carboxylic acid group.
2. Aldehyde group.
3. Alcohol group.
4. Ketone group.

Ethene decolourises bromine water because ethene is an alkene. And all alkenes and alkynes are unsaturated compounds which decolourise bromine water. On the other hand, ethane being an alkane is a saturated compound which does not decolourise bromine water.

The most unique property of carbon atom is its ability to combine itself, atom to atom to form long chains. This property of self combination is useful to us because it gives rise to an extremely large number of carbon compounds (or organic compounds).

Coal and petroleum are called fossil fuels because they are produced through the decomposition of the pre-historic organisms (plants and animals) buried deep in the soil since millions of years ago.

Due to its softness, powdered graphite can be used a lubricant whereas diamond being extremely hard can not be used as lubricant.

1. Vegetable oil (like castor oil, cottonseed oil or soyabean oil).
2. Sodium hydroxide (caustic soda).
3. Sodium chloride (common salt).

	Soaps	Detergents
i.	Soaps are biodegradable.	Detergents are not biodegradable.
ii.	Soaps have relatively weak cleansing action.	Detergents have a strong cleansing action.

When soap is used for washing clothes with hard water, a large amount of soap in water reacts with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum. This makes the cleaning of clothes difficult.

Buck minster fullerene is an allotrope of carbon containing clusters of 60 carbon atoms joined together to form spherical molecules. It burns on heating to form carbon dioxide and nothing is left behind. This shows that it is made up of carbon only like diamond and graphite.

Litmus test: Some blue litmus solution is added to the organic compound (to be tested). If the blue litmus solution turns red, it shows that the organic compound is acidic in nature and hence it is a carboxylic acid (ethanoic acid). Ethanol has no effect on any litmus solution.

Detergents are better cleansing agents than soaps because they do not form insoluble calcium and magnesium salts with hard water, and hence can be used for washing even with hard water.

Disadvantages of incomplete combustion:

1. It leads to the formation of soot which is nothing but unburnt carbon which pollutes the atmosphere, blackens cooking utensils.
2. It leads to the formation of an extremely poisonous gas called carbon monoxide.

1. X is ethanol.
2. Y is ethanoic acid.
3. Z is ethyl ethanoate

Ethanol reacts with ethanoic acid to form ethyl ethanoate ester.

Harmful effects of drinking alcohol:

1. Alcohol slows down the activity of the nervous system and brain due to which the judgement of a person is impaired and his reaction becomes slow.
2. Heavy drinking of alcohol on a particular occasion leads to staggered movement, slurred speech and vomiting.

Diamonds are used for making jewellery. Graphite is used for making pencil cores or ‘pencil leads’.

Carbon and its compounds are used as fuels because they burn in air releasing a lot of heat energy.