Ch.13.1

Question 1

All matter is made up of _______________________________ called _______________. They are the _______________________________________.

Answer 1

small particles, atoms, smallest units of matter

Question 2

What is an element? Give two examples.

Answer 2

It is a substance that is made up of only one kind of atom. Gold and iron.

Question 3

Apart from atoms, what else can elements be made up of? What do these consist of? Give two examples.

Answer 3

Molecules; atoms of the same kind; hydrogen, sulphur.

Question 4

What are three ways in which molecules differentiate in?

Answer 4

The type of element, the number of atoms, and the ways of combinations.

Question 5

What are the models that represent molecules and atoms called?

Answer 5

Ball-and-stick models.

Question 6

Can atoms be broken down? How about molecules?

Answer 6

No; yes.

Question 7

A total of _____ elements have been identified by 2017. Among these elements, _____ of them occur naturally and the rest have been ___________________________________.

Answer 7

118, 92; made by scientists in laboratories

Question 8

What are chemical symbols?

Answer 8

They are specific symbols that represents each element.

Question 9

How many letters are usually found in a chemical symbol? Where do these letters come from and how are they written in?

Answer 9

One or two; they come from the element’s English or Latin name, and the first letter is always written in UPPER CASE; and the second, in lower case.

Question 10

A molecule can be represented by a ___________________________. The _____________ of it indicates ___________________________.

Answer 10

chemical formula; subscript; the number of atoms it contains.

Question 11

Elements can be classified as _________________, _________________ and _________________ based on their _________________ _________________.

Answer 11

metals, non-metals, semi-metals, physical properties.

Question 12

Name and describe the 9 physical properties of metals.

Answer 12

Physical state: Most metals are solids at room temperature
Appearance: Most metals are shiny in appearance
Strength: Most metals are strong
Melting and boiling points: Most metals have high melting points and high boiling points
Density: Metals have high densities; Most metals are denser than water (1g/cm3), so they will sink in water
Thermal conductivity: Metals are good conductors of heat
Electrical conductivity: Metals are good conductors of electricity
Malleability: Metals are malleable (can be bent or pressed into different shapes)
Ductility: Metals are ductile (can be pulled into wires)

Question 13

Why isn’t magnetisability a physical property of metals? Support your answer with examples.

Answer 13

This is because not all metals can be attracted by magnets. While some, such as iron, nickel and cobalt can, others, such as copper, cannot.

Question 14

What is the only metal that is not a solid at room temperature? Instead, which physical state is it in?

Answer 14

Mercury; It is a liquid.

Question 15

Name and describe the 7 physical properties of non-metals.

Answer 15

Physical state: Most non-metals are solids or gases at room temperature; over half of them are gases.
Appearance: Non-metallic solids are usually dull in appearance.
Strength: Non-metallic solids are usually brittle.
Melting and boiling points: Non-metals usually have low melting points and boiling points.
Density: Non-metals usually have low densities.
Thermal conductivity: Non-metals are usually poor conductors of heat.
Electrical conductivity: Non-metals are usually poor conductors of electricity.

Question 16

What is the only non-metal that is not a solid nor a gas at room temperature? Instead, which physical state is it in?

Answer 16

Bromine; liquid.

Question 17

What are semi-metals? Give two examples of them.

Answer 17

They are elements that have properties of both metals and non-metals. Boron, silicon.

Question 18

Explain why semi-metals are semi-conductors of electricity. Name one example of a semi-metal that is widely used as a semi-conductor.

Answer 18

This is because under normal circumstances, they do not conduct electricity; However, when they are mixed with a small amount of an impurity, they conduct electricity quite well.
Silicon; it is widely used in the electronics industry to make computer chips.

Question 19

Describe and name a metal that is an exception to the physical properties of metals.

Answer 19

Sodium; it is so soft that it can be cut easily with a knife, and it has a low melting point.

Question 20

Describe and name a non-metal that is an exception to the physical properties of non-metals.

Answer 20

Carbon can exist in different forms.
Diamond, a form of carbon is the hardest natural substance, very shiny, and has extremely high melting and boiling points.
Graphite, another form of carbon, can conduct electricity.

Question 21

What are atoms made up of? What are they also known as?

Answer 21

Small particles that are protons, neutrons and electrons. Subatomic particles.

Question 22

Describe and name the centre of an atom.

Answer 22

It is a very tiny and extremely dense region called the nucleus, containing tightly packed protons and neutrons.

Question 23

An atom consists mostly of _______________________ (______%), occupied by ___________________, which _____________________________________.

Answer 23

empty space, 99, move very fast around the nucleus.

Question 24

What are electron shells?

Answer 24

They illustrate the route of the electrons, but they are imaginary, as there is not actual route for electrons to follow.

Question 25

What are the symbols for protons, neutrons and electrons respectively?

Answer 25

p(⁺), n and e⁻.

Question 26

What are the masses of protons, neutrons and electrons relative to that of a proton respectively?

Answer 26

1, around 1, negligible (around 1/1800)

Question 27

What are the electrical charges of protons, neutrons and electrons relative to that of a proton respectively?

Answer 27

1, 0, -1

Question 28

What are the positions of protons, neutrons and electrons in an atom respectively?

Answer 28

Inside the nucleus, inside the nucleus, moves around the nucleus.

Question 29

Why are we usually not interested in finding the absolute mass of an atom?

Answer 29

This is because they are too light.

Question 30

Why are atoms electrically neutral?

Answer 30

This is because an atom has an equal number of protons and electrons, which carry the opposite charge of the same magnitude; hence the positive and negative charges cancel out each other.

Question 31

The radius of an atom is about _____________ times the radius of a nucleus.

Answer 31

20000

Question 32

Compare the size of an atom and its nucleus with an analogy.

Answer 32

If the atom were a football stadium, its nucleus would be the size of a pea at the centre.

Question 33

Each element has its own unique _______________________ (___), which is equal to the _______________________ in the atom.

Answer 33

atomic number, Z, number of protons

Question 34

The mass number (___) of an atom refers to the __________________ + ___________________ in the atom. Which type of subatomic particle is not included in this formula? Why?

Answer 34

A, number of protons, number of neutrons; Electrons, this is because they are so light that their mass is negligible.

Question 35

When does an atom become charged? What is formed?

Answer 35

This happens if an atom loses or gains one or more electrons; a positively or negatively charged ion is formed.

Question 36

In general, atoms of metals tend to _______________________. Name an example and represent its process with an equation.

Answer 36

Lose electrons; sodium: Na —> Na⁺ + e⁻

Question 37

On the other hand, atoms of non-metals tend to _______________________. Name an example and represent its process with an equation.

Answer 37

gain electrons; chlorine: Cl + e⁻ —> Cl ⁻

Question 38

How can we check equations of ions?
—
—

Answer 38

—see if the equation has a balanced charge

—never use minus signs