Explanation

The tropopause is the layer that separates the stratosphere and troposphere.

It's a boundary layer located at an average altitude of around 12 km (7.5 miles) above the Earth's surface, where the troposphere ends and the stratosphere begins.

Explanation

Polyethene, also known as polyethylene, is a type of plastic.

It is a thermoplastic polymer made from ethylene monomers.

It is commonly used in packaging, plastic bags, and containers.

Explanation

Alkenes are a class of unsaturated hydrocarbons that contain one or more carbon-carbon double bonds (C=C).

This double bond is the defining feature of alkenes.

It makes them more reactive than saturated hydrocarbons (alkanes).

Explanation

A centrifuge is a machine that uses centrifugal force to separate particles of different densities or sizes from a mixture.

It is commonly used to separate:

• Liquids from solids (e.g., mud, sludge)
• Heavy particles from lighter particles (e.g., sedimentation)
• Immiscible liquids (e.g., oil and water)

Explanation

Soap is a type of salt that is formed from the reaction of a fatty acid with an alkali, such as sodium or potassium hydroxide.

Fatty acids are long-chain carboxylic acids that are found in fats and oils.

Explanation

Temporary hard water is caused by the presence of dissolved calcium and magnesium bicarbonates (Ca(HCO3)2 and Mg(HCO3)2).

These salts are commonly found in natural water sources and can enter the water supply through contact with limestone, dolomite, and other mineral deposits.

Explanation

Explanation

Abrasives are substances that wear away or remove material through friction or rubbing.

Examples of abrasives include:

Water insoluble minerals like:

• Silica (sand)
• Alumina (aluminum oxide)
• Calcium carbonate (limestone)
• Diamond

Explanation

Systematic errors are caused by faulty or improper functioning of instruments, or by a flaw in the experimental design.

These errors are consistent and repeatable, and can be identified and corrected.

Explanation

When the magnitude of Kc (equilibrium constant) is small, it indicates that the reaction mixture contains mostly reactants, and the forward reaction does not proceed very far.