rmg'kwjw Flashcards

1
Q

how are compounds created ?

A

when different elements link together in definite proportions

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2
Q

How many molecules are in the following element:

CH4
methane

A

1 carbon molecule (C)

bonded to 4 hydrogen molecules (H) (4)

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3
Q

Chemical bonding involves the ________ _______ of each atom

A

Outer electrons

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4
Q

the outer electrons are used to _______

A

form chemical bonds

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5
Q

How to determine if something is an element or not ?

A

Elements cannot be further broken down to a simpler form and are listed on the periodic table

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6
Q

These OUTERMOST electrons are the only electrons that form chemical bonds

name them

A

Valence electrons

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7
Q

the ____ of valence electrons in an atom helps determine the type and ______of _____ the atoms can form

A. Type / form / bonds
B. Number / form / bonds
C. Number / number / bonds

A

C.

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8
Q

how can the periodic table tell you the number of valence electrons an atom has ??

A

Group 1 has 1 valence electron
Group 2 has 2 valence electrons
Group 3 has 3 valence electrons
Group 4 has 4 valence electrons

etc..

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9
Q

atoms with _ valence electrons are chemically ______. They do not react easily with other atoms

A

8

stable

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10
Q

by forming bonds atoms become … ?

A

more chemically stable

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11
Q

Fe58 26

deduce the number of electrons , protons and neutrons

A

electrons: 26
protons: 26
neutrons: 32

(Electron and proton number are the same and to find the number of neutrons subtract 26 from 58 = 32)

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12
Q

Covalent bonds is between …?

A

non-metals

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13
Q

Ionic bond is between … ?

A

at least 1 metal and non metal(s)

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14
Q

Metallic bond is between … ?

A

metals

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15
Q

why is the formula for hydrogen always written as H2

A

it is a diatomic gas (‘di’ meaning 2)

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16
Q

iron is a transition metal , state two things about iron

A

iron forms coloured compounds

iron can act as a catalyst

iron is brown when freshly cut

(remember any two)

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17
Q

ionic compounds consist of ..?

A

positive metal ion and negative non metal ion = net charge of 0

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18
Q

metallic elements tend to ____ electrons

A

lose

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19
Q

nonmetals tend to ____ electrons

A

gains

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20
Q

cations are …?

A

metallic elements.

positively charged ions (meaning they have more protons then electrons due to LOSING one or more electrons)

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21
Q

anions are … ?

A

nonmetals.

negatively charged ions (due to having GAINED one or more electrons)

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22
Q

Complete the chemical equation for this reaction……………….+ 2KI →I2+ ……………KCl

A

CL2 + 2KL –> l2+ 2KCl

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23
Q
4.Which process involves a physical change? 
A. heating calcium carbonate 
B. burning wood 
C. melting an ice cube
D. mixing an acid and a base
A

C

24
Q
5.Which element is a non-metal? 
A scandium 
B sodium 
C strontium 
D sulfur
A

D

25
Q
Some plastics are non-biodegradable. What is the meaning of the term non-biodegradable?
 A cannot be recycled for further use 
B gives off greenhouse gases when burnt
 C harmful to animals and plants 
D not broken down by natural processes
A

D

26
Q

Which statement about silicon dioxide, SiO2, is correct?
A It conducts electricity because it contains free electrons.
B it is a macromolecule with four oxygen atoms bonded to each silicon atom.
C It is a simple covalent molecule.
D Its structure is similar to graphite.

A

D

27
Q

How can you model the valence electrons of metal atoms?

A

Sea of electrons

28
Q

Why are metals good conductors ?

A

Metals are good conductors of electric current because electrons can flow freely in the metal.

29
Q

Which metals have a hexagonal close-packed crystal structure

A

magnesium
zinc
cadmium
etc…

30
Q

What are alloys ?

A

mixture of two or more elements and at least one of them is a metal

31
Q

example of an alloy ?

A

Brass

combination of copper and zinc

32
Q

Does diamond conduct electricity ?

A

No diamond does not conduct electricity because it is a non-metallic element

33
Q

diamond has a very ____ _______ point

A

high melting

34
Q

carbon doesn’t conduct electricity. Carbon, graphite and diamond have the same giant molecular crystal structures. Does graphite conduct electricity ?

A

Graphite is a form of carbon that does conduct electricity

35
Q

why can graphite be used as a lubricant / feel slippery

A

because between the layers of sheets, there are weaker forces of attraction. This means that the layers are able to slide over each other easily.

36
Q

What names would you give these compounds?

1) NaI
2) MgS
3) NO

A

1) sodium iodide
2) magnesium sulphide
3) Nitrogen oxide

37
Q

how to determine if something is in
-ite
-ate
or -ide

A

______ide is used for non-metal compounds generally
______ate and _____ite is used for polyatomic ions of oxygen.
-ate is used for the ion that has the largest number of Oxygen atoms.
-Ite is used for the ion that has the smallest number of oxygen atoms

38
Q

during a chemical change the composition of matter ______ changes

A

always

39
Q

A substance present at the start of the reaction is a ..?

A

reactant

40
Q

substance produced in the reaction is a ..?

A

product

41
Q

During a physical change, the composition of the matter _____ changes.

A

never

42
Q

what are four clues a chemical change has taken place ?

A
  1. transfer of energy
  2. change in colour
  3. the production of gas
  4. formation of a precipitate
43
Q

transfer of energy is ?

A

exothermic

44
Q

gaining of energy is ?

A

endothermic

45
Q

Why is diamond much harder than graphite?

A

because of the covalent bonds that extend in all directions through the crystal.

46
Q

Why can graphite Conduct electricity

A

Because of the different carbon arrangements

47
Q
What is the symbol of the metal used in the manufacture of aircraft because of its strength and low density?
 A. Al                             
 B. Cu                              
C. Fe                            
  D. Zn
A

answer A. = aluminum

48
Q

Rusting of an article made up of iron is called
A. corrosion and it is a physical as well as chemical change
B. dissolution and it is a physical change
C. corrosion and it is a chemical change
D. dissolution and it is a chemical change

A

C

49
Q

Which of the following are physical changes?

(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal

A (i), (ii) and (iii)
B (i), (ii) and (iv)
C(i), (iii) and (iv)
D(ii), (iii) and (iv)

A

c.

50
Q

Bronze is used for making medals
.A True
B False

A

a

51
Q
Which of the following models can describe the valence electrons of metals?
A. A body -centered cube
B. Octets of electrons
C. A rigid array of electrons
D. A sea of electrons
A

d

52
Q

Alloys usually consists of more than one metal combined
A. True
B. False

A

false

53
Q
The “lead” in a pencil is made of a mixture of graphite and clay. When the percentage of graphite is increased, the pencil slides across the paper more easily.Which statement explains this observation?
A. Graphite has a high melting point
B. Graphite is a form of Carbon    
 C. Graphite is a lubricant
D, Graphite is a non –metal
A

c

54
Q

what are beakers used for ?

A

hold solids and liquids but they are not accurate so they are used to measure the volume of things

55
Q

what are bunsen burners used for ?

A

heating non-volatile liquids and solids