Chemical Reaction | MCQs

Explanation

• The reactants in the reaction are Methane (CH4) and Oxygen (O2).
• These two substances combine to form the products Carbon Dioxide (CO2) and Water (H2O), releasing energy in the process.

Explanation

• A chemical reaction is a process in which one or more substances are converted into new substances, often with a change in chemical composition and properties.
• Chemical reactions involve the breaking and forming of chemical bonds, resulting in a transformation of the original substances.

Explanation

• Leaves changing colors in the fall is an example of a chemical reaction.
• During this process, the production of chlorophyll (the green pigment) slows down, and the production of other pigments.
• Like carotenoids and anthocyanins increases, causing the leaves to change color.

Explanation

• The incorrect statement is: States of matter does not change during chemical reactions.
• During chemical reactions, states of matter can change.
• For example, a solid may dissolve in a liquid, a liquid may vaporize, or a gas may condense into a liquid.

Explanation

• When a metal bubbles when placed in an unknown liquid, it indicates that a chemical reaction has taken place.
• Bubbling is often a result of a gas being released during a reaction.
• In this case, the metal is reacting with the unknown liquid to produce gas, causing the bubbling effect.
• This is a clear indication that a chemical reaction has occurred.

Explanation

• Burning of wood is a chemical change, as it involves a chemical reaction between the wood and oxygen.
• Resulting in a change in chemical composition and the formation of new substances (ashes, carbon dioxide, water vapor, etc).

Explanation

• When fuel is burned, carbon dioxide gas (CO₂) is primarily produced.
• The combustion of fuel, particularly hydrocarbons, typically results in the formation of carbon dioxide and water vapor (H₂O).

Explanation

• Melting of ice is a physical change, as it only involves a change in state (from solid to liquid) without a change in chemical composition.

The examples of chemical changes:

• Burning of fuel
• Explosion of firework
• Burning of wood
• Cooking of food (breakfast, lunch, dinner)
• Bursting of crackers
• Burning of wax
• Rusting of iron
• Heating sulphur with iron fillings (to produce iron sulphide)
• Digestion of food
• Respiration in living things
• Photosynthesis in plants

Explanation

• A chemical change, also known as a chemical reaction.
• It is a process that alters the composition of one or more substances, resulting in the formation of new substances with different properties.

Explanation

The correct answer is: No change in composition

• A chemical change involves a transformation of one or more substances into new substances, which means a change in composition.

The signs of chemical change:

• Release of gas
• Change in color
• Change in temperature
• Change in smell
• Production of a new material