Structure and Properties of Materials

Question 1

What is an element?

Answer 1

It is a pure substance that cannot be broken down into two or more simpler substances by chemical methods.

Question 2

What can elements appear as?

Answer 2

Atoms and Molecules.

Question 3

What if an element appear as an atom?

Answer 3

If they are not chemically bonded to each other.

Question 4

What if an element appear as a molecule?

Answer 4

If they are covalent bonded.

Question 5

What is a compound?

Answer 5

It is a pure substance containing two or more elements that are chemically combined in a fixed ratio.

Question 6

What happens if elements are chemically bonded together?

Answer 6

It forms a covalent compound or an ionic compound

Question 7

What exists between atoms in molecules?

Answer 7

Chemical bonds.

Question 8

What does molecules consist of?

Answer 8

Molecules consist of either atoms of the same element or atoms of different elements.

Question 9

What is the difference between H and CO?

Answer 9

H is an element while CO is a compound

Question 10

How can compounds be separated into their constituent elements?

Answer 10

Compounds can be separated into their constituent elements by using chemical methods.

Question 11

What are the two ways to separate the compounds?

Answer 11

By thermal decomposition which is exposing the compound to strong heat or electrolysis which is passing an electric current through the compound

Question 12

What is the difference between compounds and mixtures?

Answer 12

A compound has a fixed proportion of the different types of atom it is made up of while mixtures do not have substances in fixed ratios. It can be made up of elements and/or compounds.

Question 13

How are mixtures separated into their constituents?

Answer 13

In mixtures, the elements and/or compounds are physically combined. They can be usually be separated using techniques.

Question 14

What are the types of separation techniques?

Answer 14

Filtration, chromatography and distillation.

Question 15

Are there new substances formed in separation techniques?

Answer 15

No

Question 16

What is seawater?

Answer 16

It is a mixture of salt and water.

Question 17

What is sodium chloride?

Answer 17

It is an ionic compound that is hard and able to withstand high temperature due to its structure.

Question 18

What does ionic compounds have?

Answer 18

Giant ionic crystal lattice structure.

Question 19

What does lattice consists of?

Answer 19

It consist of alternating positive and negative ions.

Question 20

What are ions held together by?

Answer 20

It is held together by electrostatic forces of attraction.

Question 21

What does ions of opposite charges have?

Answer 21

It has strong electrostatic forces of attraction between them.

Question 22

What is needed to overcome these forces?

Answer 22

A large amount of energy is needed.

Question 23

Ionic compounds tends to have what?

Answer 23

It tends to have very high melting and boiling points.

Question 24

What state they’re in at room temperature?

Answer 24

Solid.

Question 25

What does the strong forces of attraction between oppositely charged ions do to ionic compounds?

Answer 25

It makes the ionic compounds resistant to deforming.

Question 26

What forces the ions to do?

Answer 26

It forces the ions to resist motion.

Question 27

What happens when enough force is applied to ions?

Answer 27

The ions move away from their lattice positions

Question 28

What happens when the repulsive forces between ions of the same charge become larger then the attractive forces?

Answer 28

The lattice structure will shatter.

Question 29

What happens when ionic compounds dissolve in water?

Answer 29

they are in the aqueous state

Question 30

What if the ionic compound is in the solid state?

Answer 30

The ions in the lattice are only able to vibrate about their fixed positions. Hence, the ions are not mobile.

Question 31

What if the compound is molten or in the aqueous state?

Answer 31

The ions are mobile and can conduct electricity.

Question 32

What does a substance that conducts electricity contains?

Answer 32

It contains charged particles that are free to move.

Question 33

What does alcohol and cooking gas consist?

Answer 33

It consist of simple covalent molecules.

Question 34

Atoms in molecules are held by what?

Answer 34

It is held by strong covalent bonds.

Question 35

Molecules are held together by what?

Answer 35

It is held by weak intermolecular forces of attractions.

Question 36

What is needed to overcome weak intermolecular forces of attraction?

Answer 36

Only a small amount of energy is needed to overcome it.

Question 37

What is easily overcome with a small amount of energy?

Answer 37

It is the weak intermolecular forces of attraction between molecules.

Question 38

What happens if the molecules gets larger?

Answer 38

The intermolecular forces of attraction are stronger and so the melting and boiling points are higher.

Question 39

Bromine and methane are usually insoluble and soluble in what?

Answer 39

They are usually insoluble in water and soluble in organic solvents like oil.

Question 40

Why does simple covalent substances in the solid, liquid or gaseous state do not conduct electricity?

Answer 40

That is because they do not have any mobile electrons or ions.

Question 41

What if the covalent substance is soluble in water?

Answer 41

Its aqueous solution conducts electricity due to the presence of mobile ions.

Question 42

Metal can exist as what?

Answer 42

Pure elements

Question 43

Metals can be mixed with what?

Answer 43

They can be mixed with other elements to produce alloys

Question 44

What is an alloy?

Answer 44

An alloy is a mixture of a metal with one or more other elements

Question 45

What does the irregular arrangement of atom sin alloys lead to?

Answer 45

It leads to the difference in properties between alloys and pure metal.

Question 46

What happens if enough force is applied to pure metals?

Answer 46

The layers of atoms can slide over one another easily.

Question 47

What happens if pure metals are hammered?

Answer 47

Pure metals can be bent or flattened into a thin sheet called malleable. They can be also be pulled into a wire without breaking which is called ductile.

Question 48

Why do alloys don't have a fixed melting point?

Answer 48

That is because alloy is a mixture and it usually melt over a range of temperatures.

Question 49

Why does most metal and alloys can conduct electricity?

Answer 49

Because metal atoms have valence electrons that are free to move throughout the structure.

Question 50

What happens if you mix different elements in varying ratios?

Answer 50

New materials with a very wide range of physical and chemical properties can be created.