Module 2: Matter, Element and Compounds

Question 1

Describe the 3 physical states of matter and their differences

Answer 1

Solid: Definite shape and volume, with particles that cling rigidly to one and another.
Liquid: Definite volume, indefinite shape, particles stick to each other but not rigid.
Gas: Indefinite volume and shape, particles move independently from one and another

Question 2

Differences between substances & mixtures: give examples

Answer 2

Substance: aka pure, either element or compound with a fixed composition.
Mixtures: Mechanically blending two or more substances together. No chemical changes occur. Homogenous: composition uniform throughout -> salt + water = salt water.
Heterogenous: 2 distinctive phases - not uniform oil+ water -> oil on top of water, 2 layers.

Question 3

How are elements placed in the periodic table by Dimitri Mendeleev (1869)?

Answer 3

Horizontal rows (groups) - elements with similar chemical properties

Vertical row (period) - increasing atomic number

Question 4

What are the noble gases? Name them and their atomic no.

Answer 4

Helium (He) 2
Neon (Ne) 10
Kr (Krypton) 36
Xe (Xenon) 54
Rn (Radon)  86
Non metals, all with 8 valence electrons apart from Helium which has 2

Question 5

What are halogens ?

Name them.

Answer 5

Halogens are extremely reactive and cannot exist as a free form element. Forms salt when reacting with Alkali Metals and alkali earth metals. 
Fluorine (F) 9
Chlorine (Cl) 17
Bromine (Br) 35
Iodine (I) 53
Astatine (At) 85

Question 6

What is the element H ? Atomic no. ? Atomic Weight?

Answer 6

Hydrogen (1)

1.008

Question 7

What is the element C ? Atomic no. ? Atomic Weight?

Answer 7

Carbon (6)

12.0107

Question 8

What is the element N ? Atomic no. ? Atomic Weight?

Answer 8

Nitrogen (7)

14.0067

Question 9

What is the element O? Atomic no. ? Atomic Weight?

Answer 9

Oxygen (8)

15.9994

Question 10

What is the element Cl? Atomic no. ? Atomic Weight?

Answer 10

Chlorine (17)

35.4527

Question 11

What is a compound?

Answer 11

A compound is mixed substance that contains two more more elements that are chemically combined. Can be break down into simpler compound or elements.
2 types of compound: ionic + molecular

Question 12

Describe the difference between molecular and ionic compounds?

Answer 12

Ionic compound: held together by attracting forces between their positive and negatively charged ions. Positive ion: cation. Negative ion: anion.

Molecular compound: held together by covalent bonds ( sharing electron pairs between atoms)

Question 13

What are subscripts?

Answer 13

The number below the line to the right of the symbol indicates how many atoms of each element is present in the formula

Question 14

What is a diatomic molecule? Name all of them?

Hint: 7 of them in total

Answer 14

Diatomic molecules each always contain two atoms (alike or different). 
H2 (Hydrogen) 
N2 (Nitrogen) 
O2 (Oxygen) 
F2(Fluorine) 
Cl2 (Chlorine)
Br2 (Bromine)
I2 (Iodine)