Science [2 Mark Questions]

1.  

1. Smells like vinegar.
2. Turns blue litmus red.

2.  

1. Brisk effervescence.
2. Evolution of colourless gas.

Physical properties−

1. Smell like vinegar.
2. Colourless liquid.

Chemical propertirs−

1. Turns blue litmus red.
2. Gives brisk effervescence with sodium carbonate.

Binary fission is the type of reproduction in which two individuals are formed from a single parent. In the process, the identity of the parent is lost.

This type of reproduction starts with karyokinesis (a division of nucleus).

Test tube A contains dil. HCl and test tube B contains dil. NaOH. On adding blue litmus solution to both the test tubes, the colour of the test tube A will change from blue to red. This is because HCl is an acid and acids turn blue litmus to red.

Plaster of Paris has a very remarkable property of setting into a hard mass on wetting with water. So, when water is added to plaster of Paris, it sets into a hard mass in about half an hour. The setting of plaster of Paris is due to the hydration crystals of gypsum, which set to form a hard, solid mass.

1. Wasp stings are alkaline in nature since they are treated using acids like vinegar.
2. Bee stings are acidic in nature since they are treated using bases like baking soda.

1. Milk is made slightly alkaline so that it may not become sour easily due to the formation of lactic acid in it.
2. The alkaline milk takes a longer time to set into curd because the lactic acid being formed has to first neutralise the alkali present in it.

Curd and other sour substances contains acids which can react with the metals of brass and copper vessels to form toxic (poisonous) metal compounds which can cause food poisoning and damage our health.

Those substances whose smell (or odour) changes in acidic or basic solutions are called olfactory indicators. Onion and vanilla extracts are olfactory indicators. When a basic solution like sodium hydroxide solution is added to a cloth strip treated with onions (or onion extract), then the onion smell cannot be detected.

When an acid or base solution is added to the universal indicator, it produces a new colour which is used to find the pH value of the acid or the base solution by matching the colour with the colours on pH colour chart.

Acid present in ant sting is formic acid which is also named as Methanoic acid.
Chemical formula for formic acid is HCOOH.
It is acidic in nature, so an alkaline compound like wet baking soda can be used to neutralize its effect to get relief from discomfort.

A salt is a compound formed from an acid by the replacement of the hydrogen in the acid by a metal.
Example: Sodium chloride – NaCl; It is obtained from hydrochloric acid and sodium metal. Ammonium chloride – NH Cl; It is obtained from ammonia and hydrochloric acid.

Acidic solution will turn blue litmus red; This red litmus will turn blue in basic solution; Distilled water will have no effect on any type of litmus pape,

Our stomach produces hydrochloric acid. If there is excess of hydrochloric acid in the stomach, it causes indigestion which produces pain and irritation. Its effect can be cured by taking antacids.

Acids produce hydrogen ions or hydronium ions only in presence of water. Therefore, it shows acidic behavior only presence of water.

Bacteria change the fresh milk into curd by producing lactic acid. Because of the presence of lactic acid in curd, the pH will come down from 6 to lower value.

1. It is used for disinfecting drinking water supply.
2. It is used in the manufacture of chloroform.

When baking powder mixes with water, then sodium hydrogencarbonate reacts with tartaric acid to evolve carbon dioxide gas which gets trapped in the wet dough and bubbles out slowly making the cake soft and spongy.

Add phenolphthalein to a portion of each solution in separate test tube. If it turns pink, the beaker contains base whereas if it remains colourless, it is an acid.
If phenolphthalein is not available, pH paper can be used. Acid will turn pH paper red base will turn pH paper blue.

Substance X is tartaric acid. It can react with any sodium carbonate formed and neutralise it otherwise cakes and bread will taste bitter.

Acetic acid is weak acid becoz it produces less hydrogen ions and ammonia is weak base becoz it produces less OH ionsExplanation:
If an acid which is less than 100% ionizes in solution is known as weak acid. For example: If a base which is less than 100% ionizes in solution is known as weak base. For example: Acetic acid is dissociates into ions but it does not ionize 100% therefore it is considered as weak acid. Ammonia dissociates into ions but it does not ionize 100% therefore it is considered as weak base.

Universal indicator is a mixture of many different indicators which gives different colours at different pH values of the entire pH scale. It is used to obtain an idea of how acidic or basic a substance is.

Acids are very reactive as they contain reactive hydroxide ions.
When reactive metals are in contact with acids they react and produce metallic salt and hydrogen gas is liberated.
Metal + Acid → Metallic salt + Hydrogen gas
Hence acids are not stored in the metallic container.

Gypsum is calcium sulphate dihydrate, CaSO.2H O. When gypsum is heated to a temperature of 100?C, it loses 3/4th of its water of crystallisation and forms plaster of Paris.

1. Neither solution will turn blue litmus red. Solution P is sodium chloride, formed from a strong acid, hydrochloric acid (HCl), and a strong base, sodium hydroxide (NaOH). When sodium chloride is dissolved in water, it gets hydrolysed to give equal amounts of hydroxide and hydrogen ions, which makes its aqueous solution neutral. Therefore, the solution of sodium chloride will have no effect on red or blue litmus paper.
2. Sodium hydroxide solution (Q) will turn red litmus blue, because solution Q is basic.

Organic acids: Citric acid, lactic acid;
Mineral acids: Hydrochloric acid, sulphuric acid.

1. It is used as cleansing agent for domestic purposes.
2. It is used for removing permanent hardness of water.