Answer key

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Last edited 25 days ago by Learn LoopHQ.

Chapter: 03. Elements And Compounds

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The 117th element, Tennessine, was created by bombarding calcium ions on a berkelium target.

Water is known as a universal solvent.

The symbol O_2 represents one molecule of oxygen.

Copper is mixed with zinc to produce brass.

Common salt / Sodium chloride is used in food to add taste.

The lead in pencils is made of graphite.

A compound is a pure substance made up of two or more elements chemically combined in a fixed proportion by mass.

The number of atoms present in the molecule of an element is called its atomicity.

Mercury is a liquid metal.

The chemical formula of sulphuric acid is H_2SO_4.

Oxygen (O_2) is a diatomic molecule because it contains two atoms.

The symbol 2O represents two atoms of oxygen.

Ancient scientists known as alchemists used certain signs and symbols to represent elements.

Substances that have a uniform composition are called homogeneous substances.

Metals are malleable, meaning they can be hammered into thin sheets.

The chemical formula of sodium carbonate is Na_2CO_3.

Sodium and potassium are soft metals.

Pure substances have fixed melting and boiling points.

Gaseous elements that do not react chemically with other elements are called noble or inert gases.

The smallest unit of a compound that exhibits all the properties of that compound and has an independent existence is called a molecule.

Bromine is the only non-metal found in the liquid state.

Ozone (O_3) is an example of a triatomic molecule.

The property that makes gold suitable for fine jewellery is its lustre.

A chemical formula also gives us information about the mass of one molecule of the compound.

Copper wires are made possible because metals are ductile.

Graphite, a form of carbon, is a good conductor of electricity.

An element is a pure substance made up of only one kind of atoms.

Water is formed by the combination of hydrogen and oxygen in a fixed ratio of 1:8 by mass.

The abbreviation used to denote an element is called a symbol.

John Dalton was the first scientist who used symbols to represent elements.

The components of a compound can only be separated by using chemical methods.

The formula of bromine molecule is Br_2.

Sulphur (S_8) is an example of a polyatomic molecule.

Elements that show some properties of metals and some properties of non-metals are called metalloids.

Nitrogen comprises nearly 78 % of all gases in the air.

Diamond is an extremely hard non-metal.

The symbol of Iron is Fe, which is derived from its Latin name Ferrum.

Oxygen is found in greatest amount in the earth’s crust.

Metals typically produce a ringing sound when struck, a property known as sonorousness.

A pure substance is a substance that contains same kind of particles.

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