Elements, Compunds, Mixtures

Question 1

Define an element

Answer 1

An element is a substance made of only one type of atom.

Examples of elements include aluminium, bromine, and carbon.

Question 2

What are some uses of common elements?

Answer 2

Common elements are used for various purposes:
* Aluminium - making airplanes and buildings
* Bromine - photography and medicines
* Carbon - found in coal, oil, and gas.

Each element has specific applications based on its properties.

Question 3

List the physical properties of metals.

Answer 3

• Good conductors of heat and electricity
• Strong and tough
• Solid at room temperature (except mercury)
• Lustrous (shiny appearance)
• Malleable
• Ductile

Malleability means they can be shaped without breaking, and ductility means they can be drawn into wires.

Question 4

What are the chemical properties of metals?

Answer 4

• Usually high density
• Can form alloys
• Some react with air and corrode (e.g., iron)
• Highly reactive metals (e.g., sodium, potassium) stored in oil
• Less reactive metals (e.g., gold, silver, platinum) do not tarnish easily
• Produce metal oxide and hydrogen gas when reacting with water
• Soluble metal oxides create metal hydroxide in water
• React with acids to produce salt and hydrogen.

The reactivity of metals varies significantly.

Question 5

Describe the general properties of nonmetals.

Answer 5

• Brittle
• Dull
• Poor conductors of heat and electricity
• React more with metals than with nonmetals
• May be solids, liquids, or gases at room temperature
• Not tough or strong.

Nonmetals exhibit a range of physical states and properties.

Question 6

Correctly write the chemical symbols for nitrogen and water.

Answer 6

N2 for nitrogen and H2O for water.

Chemical symbols represent elements and compounds.

Question 7

How can atoms be arranged in elements?

Answer 7

Atoms can be arranged as:
* Single atoms
* Molecules
* Lattices.

Molecules are groups of atoms bonded together, while lattices refer to a crystal structure.

Question 8

Define a molecule.

Answer 8

A molecule is a cluster of two or more atoms bonded together.

In molecular elements, the molecules are composed of the same type of atom.

Question 9

Describe the molecular structure of nitrogen.

Answer 9

Nitrogen has a molecular structure represented as N2, consisting of two nitrogen atoms tightly bonded together.

This is an example of a diatomic molecule (means composed of only two atoms).

Question 10

Explain the molecular structure of phosphorus.

Answer 10

In phosphorus, each P atom in P4 is linked to three other phosphorus atoms in a tetrahedral structure.

This arrangement allows for stability and unique properties.

Question 11

What is the molecular structure of sulfur?

Answer 11

Sulfur atoms form cyclic octatomic molecules with the chemical formula S8.

This means eight sulfur atoms are arranged in a ring.

Question 12

Describe the structure of carbon.

Answer 12

Carbon has a tetrahedral structure, with each carbon atom covalently bonded to four other carbon atoms at the corners of the tetrahedron.

This arrangement is fundamental to organic chemistry.

Question 13

Do all metals exist as crystal lattices?

Answer 13

Yes, all metals exist as crystal lattices.

This is a key characteristic of metallic bonding.

Question 14

Define compounds.

Answer 14

Compounds are substances made up of more than one type of atom.

They can be further classified into molecular compounds and compound lattices.

Question 15

Differentiate between molecular compounds and compound lattices.

Answer 15

A molecular compound is a discrete group of two or more atoms, while a crystal lattice is a large collection of atoms, ions, or molecules arranged in a highly ordered repeating pattern.

This distinction is crucial in chemistry.

Question 16

Distinguish between elements, compounds, and mixtures.

Answer 16

• Element - pure substance with identical atoms or molecules
• Compound - pure substance with identical molecules of two or more types of atoms
• Mixture - material with two or more types of molecules that can be separated physically.

The properties of each type vary significantly.

Question 17

Define molecular formula and provide an example.

Answer 17

A molecular formula gives the total number of atoms of each element present in a molecule, e.g., H2O.

Molecular formulas are essential for understanding chemical composition.

Question 18

Define the term ‘mixture’.

Answer 18

A mixture is when two or more materials are mixed together but do not chemically combine, retaining their original properties.

Mixtures can be separated by physical means.

Question 19

What is a solution?

Answer 19

A solution is when particles of another solid or liquid dissolve into each other, appearing clear.

Solutions are homogeneous mixtures.

Question 20

Define solute.

Answer 20

A solute is the substance being dissolved in a solution.

Solutes can be solids, liquids, or gases.

Question 21

Define solvent.

Answer 21

A solvent is the substance in which the solute is being dissolved.

Solvents are usually liquids, with water being the most common.

Question 22

What is an aqueous solution?

Answer 22

An aqueous solution is one where water is the solvent.

This is a common context in chemistry.