General Science Questions For Competitive Exams

The lightest or least dense metal that is a pure element is lithium, which has a density of 0.534 g/cm³.

Air is a mixture of many gasses present in the atmosphere. Air consists of carbon dioxide, nitrogen, oxygen etc.

Biogas is primarily composed of methane gas, carbon dioxide, and trace amounts of nitrogen, hydrogen, and carbon monoxide.

Nitrous oxide, commonly known as laughing gas or nitrous, is a chemical compound, an oxide of nitrogen with the formula N ₂O. At room temperature, it is a colourless non-flammable gas, with a slight metallic scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidizer similar to molecular oxygen.

Aluminium is the third most abundant element (after oxygen and silicon) and the most abundant metal in earth’s crust.

Sodium bicarbonate, regular or ordinary used on class B and C fires, was the first of the dry chemical agents developed. In the heat of a fire, it releases a cloud of carbon dioxide that smothers the fire. That is, the gas drives oxygen away from the fire, thus stopping the chemical reaction.

Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in structure.

lead. …is in the manufacture of storage batteries. It is used in ammunition (shot and bullets) and as a constituent of solder, type metal, bearing alloys, fusible alloys, and pewter.

Water. An especially notable irregular maximum density is that of water, which reaches a density peak at 3.98 °C (39.16 °F).

Sodium carbonate, Na₂CO₃, (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na₂CO₃ and its various hydrates. All forms are white, water-soluble salts.

A pencil is an implement for writing or drawing. It is a thin core of graphite well mixed with clay, inside a wooden body as protective casing that prevents the core from being broken.

Azurite is not an ore of aluminum.

Sodium is kept immersed in kerosene because Sodium doesn’t react with kerosene.

Hardness can be removed by adding sodium carbonate (washing soda) or by passing the water through an ion-exchange column. Hardness in water is caused by dissolved magnesium ions and calcium ions.

Mercury remains in liquid form under normal conditions. Mercury remains in the form of liquid in room temperature.

Methane, especially as generated by decaying matter in marshes.

Wrought Iron is the purest form of iron. It contains 0.12 to 0.25% carbon and is thus the purest form of iron.

Bell metal is a hard alloy used for making bells and related instruments, such as cymbals. It is a form of bronze with a higher tin content, usually in approximately a 4:1 ratio of copper to tin (typically, 78% copper, 22% tin by mass).

Methane explosions occur when a buildup of methane gas contacts a heat source and there is not enough air to dilute the gas level below its explosion point.

Photovoltaics (PV) use silicon solar cells to convert the energy of sunlight into electricity. Operates under the photoelectric effect which results in the emission of electrons.

Elements known to be present on the lunar surface include, among others, oxygen (O), silicon (Si), iron (Fe), magnesium (Mg), calcium (Ca), aluminium (Al), manganese (Mn) and titanium (Ti).

Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in structure.

In old Igneous type of rocks metals like gold and copper mostly found. Gold and copper are found in ore bodies associated with porphry.