A Quick Science Quiz For High School Students!

Explanation
Elements with the same number of outer electrons have similar chemical properties. This is because the outermost electrons, also known as valence electrons, are the ones involved in chemical reactions and bonding. Elements with the same number of outer electrons have the same electron configuration in their outermost energy level, which determines their reactivity and ability to form chemical bonds. Therefore, elements with the same number of outer electrons exhibit similar chemical behavior and properties.

Explanation
When carbon dioxide is bubbled through limestone, it reacts with the calcium carbonate present in the limestone to form calcium hydroxide. This reaction causes the limewater to turn cloudy. Therefore, the correct answer is limewater.

Explanation
Metals that are more reactive than carbon cannot be extracted by carbon reduction method as carbon is not strong enough to displace these metals from their compounds. Therefore, electrolysis is used as a method to extract these metals. In electrolysis, an electric current is passed through a molten compound or an aqueous solution containing the metal ions, causing the metal ions to be reduced and deposited at the cathode. This process allows for the extraction of highly reactive metals such as sodium, potassium, and aluminum.

Explanation
During the complete combustion of hydrocarbons, the carbon and hydrogen atoms present in the hydrocarbons combine with oxygen from the air. This reaction results in the formation of carbon dioxide (CO2) and water vapor (H2O). Therefore, the correct answer is water vapor.

Explanation
Bromine water will decolourise when shaken with alkenes. This is because alkenes are unsaturated hydrocarbons that contain a double bond between carbon atoms. Bromine water is a solution of bromine in water, and bromine is a reddish-brown liquid. When bromine water is shaken with alkenes, the double bond in the alkene reacts with bromine, causing the bromine molecules to break apart and attach to the carbon atoms. This reaction leads to the decolourisation of bromine water, as the reddish-brown bromine molecules are converted into colorless products.

Explanation
Plant oils can be hardened to make margarine by reacting them with hydrogen using a nickel catalyst at 60⁰C. This process is known as hydrogenation. Hydrogenation involves adding hydrogen atoms to unsaturated fats in the oil, which converts them into saturated fats. This makes the oil more solid and gives it a higher melting point, resulting in the formation of margarine. The nickel catalyst helps to speed up the reaction and make it more efficient.

Explanation
Plants remove carbon dioxide from the atmosphere through photosynthesis. During photosynthesis, plants use sunlight, water, and carbon dioxide to produce glucose and oxygen. The carbon dioxide is absorbed by the plant through tiny openings called stomata on the leaves. This process helps in reducing the amount of carbon dioxide in the atmosphere, which is important for maintaining a balance in the Earth's climate.