Complete the statement by filling the gaps using an appropriate term from the terms given in the bracket. (slow, coloured, arrow, fast, smell, milky, physical, product, chemical, reactant, covalent, ionic, octet, duplet, exchange, sharing, equality sign)

a. An ................ is drawn in between the reactants and products while writing the equation for a chemical reaction.

b. Rusting of iron is a ..................... chemical change.

c. The spoiling of food is a chemical change which is recognized from the generation of certain ............ due to it.

d. A colourless solution of calcium hydroxide in a test tube turns ..... on blowing in it through a blow tube for some time.

e. The white particles of baking soda disappear when put in lemon juice. This means that it is a .......... change.

f. Oxygen is a ................. in respiration.

g. Sodium chloride is ........... compound while hydrogen chloride is ......... compound.

h. Electron ......... is complete in each hydrogen in a hydrogen molecule.

i. Chlorine (Cl₂) molecule is formed by ............... of electrons between two chlorine atoms.

(a) An Arrow is drawn in between the reactants and products while writing the equation for a chemical reaction.

Explanation: An arrow in a chemical equation points to the substance formed. The arrow in a chemical reaction specifies the direction of the chemical reaction. The substances used as reactants is written on the left side while the products are written on the right of the arrow.

(b) Rusting of iron is a Slow chemical change.

Explanation:

Reactions can be classified as fast reactions and slow reactions. Slow reaction proceeds in a rather slower than normal reactions. The turning of Iron into rust requires time and hence the reaction is a slow one.

(c) The spoiling of food is a chemical change which is recognized from the generation of certain Smell due to it.

Explanation:

During a chemical change, composition of matter changes and new products with different properties are developed. During the spoiling of food, the food substance get converted to a different product which changes the smell and deteriorates quality. Hence spoiled foods can be identified from their smell.

(d) A colourless solution of calcium hydroxide in a test tube turns Milky on blowing in it through a blow tube for some time.

Explanation:

On blowing into a test tube that contains calcium hydroxide, Carbon Dioxide from our exhaling air reacts with the calcium hydroxide present. The air that we exhales contains Carbon Dioxide as a result of respiration and this reacts with calcium hydroxide forming a milky precipitate.

(e) The white particles of baking soda disappear when put in lemon juice. This means that it is a Chemical change.

Explanation:

Baking soda is an alkali. It get neutralised on treating with lemon juice that contains Citric acid. This reaction results in the evolution of CO₂ and a salt that is soluble. Since a new product is formed from the reactants used, the change is a chemical change.

(f) Oxygen is a Reactant in respiration

Explanation:

Respiration is a chemical change that involves the breakdown of Glucose into other smaller molecules in the presence of oxygen. Glucose reacts with oxygen to form CO₂ and H₂O during respiration. The chemical change is shown as:

C₆H₁₂O₆ + O₂CO₂ + H₂O.

Since O₂ lies in the left side it is considered to be a reactant.

(g) Sodium chloride is Ionic compound while hydrogen chloride is Covalent compound.

Explanation:

During the formation of Sodium Chloride, chlorine atom gains an electron from the sodium atom so as to complete its octet. This results in Sodium being positively charged and Chlorine being negatively charged and thus forms an ionic bond between them.

In the case of Hydrogen chloride, an electron is shared between Hydrogen and Chlorine so as to get a complete octet. This sharing of electron results in the formation of a covalent bond making Hydrogen Chloride a covalent compound.

(h) Electron Duplet is complete in each hydrogen in a hydrogen molecule

Explanation:

During the formation of a H₂ molecule, two H atoms come together and share an electron between them. This results in the formation of a covalent bond between each of the molecules. Since there are now two electrons available for both the hydrogen atom, that is, one proper electron and one shared electron, the duplet of the H₂ molecule is complete. The following figure explains the process:

(i) Chlorine (Cl₂) molecule is formed by the sharing of electrons between two chlorine atoms.

Explanation:

Chlorine molecule is a covalent molecule. It is formed by the sharing of electrons between the two chlorine atom so as to obtain a completely filled octet on both the chlorine atoms. The sharing of electrons between two covalent molecules make the chlorine atom a covalent compound. The formation of a chlorine molecule is shown below: