chem test (first sem)

Question 1

a particle

Answer 1

relative mass = 1
relative charge = +1
positive in atom = nucleus

Question 2

a neutron

Answer 2

relative mass = 1
relative charge = 0
positive in atom = nucleus

Question 3

electron

Answer 3

relative mass = 1/2000
relative charge = -1
positive in atom = shells

Question 4

isotope

Answer 4

• same atomic number, different mass number

Question 5

what is an element

Answer 5

an element is made up of only one atom

Question 6

lattices

Answer 6

small number of atoms (between 2-50) joined together by covalent bonds

Question 7

molecules

Answer 7

many millions of atoms joined together by covalent or metallic bonds

Question 8

compound

Answer 8

• noble gases
• a compound is a substance where 2 or more different elements are bonded by very strong covalent or ionic bonds

Question 9

characteristics of compounds

Answer 9

1. made up of 2 or more elements chemically bonded together
2. its very difficult to separate the two original elements
3. the properties (chemical + physical) are often totally different from the original element

Question 10

mixture

Answer 10

2 or more components (substances) which are mixed together but not chemically combined

Question 11

ionic bond

Answer 11

the attraction between oppositely-charge ions in a giant lattice structure

Question 12

covalent bond

Answer 12

sharing a pair of electrons between two atoms

Question 13

valency: bonding ability

Answer 13

group I = 1
group II = 2
group III = 3
group IV = 4
group V = 3
group VI = 2
group VII = 1
group VIII = 0

Question 14

common lab reagents (acids)

Answer 14

• hydrochloric acid (HCl)
• nitric acid (HNO3)
• sulphuric acid (H2SO4)

Question 15

common lab reagents (alkalis)

Answer 15

• sodium hydroxide (NAOH)
• ammonia (NH3)

Question 16

diatomic elements

Answer 16

H2, N2, O2, F2, CL2, Br, I2

Question 17

relative atomic mass

Answer 17

average mass of the atoms of an element, on a scale where carbon 12 is 12

Question 18

relative molecular mass (relative formula mass)

Answer 18

average mass or molecule on a scale where carbon 12 is 12

Question 19

mass

Answer 19

mass (g) = number of moles X molar mass (formula mass)

Question 20

characteristics of metals

Answer 20

1. metals conduct electricity
2. metals are generally shiny
3. metals have a generally high melting point
4. metals form basic oxides
   -> if they dissolve in water, they produce alkaline solution
5. malleable and ductile

Question 21

characteristics of non-metals

Answer 21

1. non conductors of electricity
2. usually not shiny
3. variety of melting/boiling points/solids are brittle
4. forms basic oxides

Question 22

metal reactivity (with oxygen)

Answer 22

metal + oxygen -> metal oxide

Question 23

metal reactivity (with water/steam)

Answer 23

metal + water -> metal hydroxide + hydrogen

Question 24

metal reactivity (with dilute acids)

Answer 24

metal + acid -> salt + hydrogen

Question 25

aluminium

Answer 25

• low density
• excellent conductor of electricity
• resistent to corrosion
  -> forms aluminium oxide on surface

Question 26

copper

Answer 26

• used in most electrical wires
• excellent conductor
• ductile
  -> drawn into thin wire

Question 27

alloys

Answer 27

• disrupts metallic structure
  -> makes mixture harder/stronger

Question 28

what is an alloy?

Answer 28

a mixture of metal and one/more other elements

Question 29

brass

Answer 29

• copper + zinc
• coins, musical instruments

Question 30

stainless steel

Answer 30

• iron + chromium + nickel
• jewellery, cooking pans, cutlery

Question 31

reactivity series (highest to lowest)

Answer 31

1. potassium
2. sodium
3. calcium
4. magnesium
5. aluminium
6. carbon
7. zinc
8. iron
9. hydrogen
10. copper
11. silver
12. gold

Question 32

methods to prevent rusting

Answer 32

• paint
• cover with plastic
• grease