Maharashtra Board Class 8 Chemical Change and Chemical Bond , This page includes Fill in the Blanks, TB Q/A, as well as Extra Questions and Answers from the chapter.
Complete the statement by filling the gaps using 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)
- An equality sign is drawn in between the reactants and products while writing the equation for a chemical reaction.
- Rusting of iron is a slow chemical change.
- The spoiling of food is a chemical change which is recognized from the generation of certain smell due to it.
- A colourless solution of calcium hydroxide in a test tube turns milky on blowing in it through a blow tube for some time.
- The white particles of baking soda disappear when put in lemon juice. This means that it is a chemical change.
- Oxygen is a reactant in respiration.
- Sodium chloride is an ionic compound while hydrogen chloride is a covalent compound.
- Electron duplet is complete in each hydrogen in a hydrogen molecule.
- Chlorine (Cl2) molecule is formed by sharing of electrons between two chlorine atoms.
Match the pairs.
- Photosynthesis i. Tendency to lose electrons
- Water ii. Reactant in combustion process
- Sodium chloride iii. Chemical change
- Dissolution iv. Covalent bond of salt in water
- Carbon v. Ionic bond
- Fluorine vi. Physical change
- Magnesium vii. Tendency to form anion
Matched Pairs:
- Photosynthesis – iii. Chemical change
- Water – vi. Physical change
- Sodium chloride – v. Ionic bond
- Dissolution of salt in water – iv. Covalent bond
- Carbon – ii. Reactant in combustion process
- Fluorine – i. Tendency to lose electrons
- Magnesium – vii. Tendency to form anion
Explain by writing a word equation.
Q- Respiration is a chemical change.
Word equation: Glucose + Oxygen → Carbon dioxide + Water
Q- Hard water gets softened on mixing with a solution of washing soda.
Word equation: Calcium chloride + Sodium carbonate → Calcium carbonate + Sodium chloride
Q- Lime stone powder disappears on adding to dilute hydrochloric acids.
Word equation: Calcium carbonate + Hydrochloric acid → Calcium chloride + Carbon dioxide + Water
Q- Bubbles are seen on adding lemon juice to baking soda.
Citric acid + Sodium bicarbonate → Carbon dioxide + Sodium citrate
Maharashtra Board Class 8 Chemical Change and Chemical Bond Extra QA
Q: Is sodium chloride an ionic or covalent compound?
A: Sodium chloride is an ionic compound.
Q: What happens during the process of rusting of iron?
A: Rusting of iron is a slow chemical change where iron reacts with oxygen and moisture to form iron oxide, commonly known as rust.
Q: What is respiration, and is it a chemical change?
A: Respiration is a biological process where glucose reacts with oxygen to produce carbon dioxide and water. Yes, it is a chemical change.
Q: How does hard water soften when mixed with washing soda?
A: Hard water softens by reacting with washing soda, forming calcium carbonate and sodium chloride.
Q: Why do bubbles appear when lemon juice is added to baking soda?
A: Bubbles form when citric acid in lemon juice reacts with sodium bicarbonate in baking soda, producing carbon dioxide gas.
