compounds

Question 1

chemical formulae

Answer 1

letters which represent the elements in the compound and numbers which tell us how many atoms of each element there are

Question 2

example of chemical formulae

Answer 2

K2SO4

Question 3

what are the elements with a 2 in their formula

Answer 3

-hydrogen H2
-nitrogen N2
-oxygen, O2
-fluorine, F2
-bromine, Br2
-chlorine, Cl2
-iodine, I2

Question 4

what are compounds

Answer 4

they are substances which are made of two or more different types of atom that are chemically joined

Question 5

what are the properties like in compounds

Answer 5

the compound has completely different properties to its constituent elements

Question 6

Carbon dioxide

Answer 6

CO2 1 carbon, 2 oxygen

Question 7

methane

Answer 7

CH4 1 carbon, 4 hydrogen

Question 8

sulphur dioxide

Answer 8

SO2 1 sulphur, 2 oxygen

Question 9

water

Answer 9

H2O 2 hydrogen, 1 oxygen

Question 10

ions

Answer 10

is an atom/ molecule that has a different number of protons to electrons, so it has a different charge.

Question 11

metal atom ions

Answer 11

need to lose electrons to gain full outer shells

Question 12

non metal ions

Answer 12

need to gain electrons

Question 13

hydrogen charge

Answer 13

+1

Question 14

oxygen charge

Answer 14

-2

Question 15

nitrogen charge

Answer 15

-3

Question 16

fluorine charge

Answer 16

-1

Question 17

relative molecule mass

Answer 17

it is a measure of the total mass of all the atoms in a molecule

Question 18

what is relative molecule mass abbreviated to

Answer 18

RMM or M

Question 19

how do you find the RMM

Answer 19

by adding all the Ar ( relative atomic mass) values in a molecule together

Question 20

percentage composition?

Answer 20

the percentage by mass of an element in a compound

Question 21

how do you work out percentage composition

Answer 21

% of element= Ar x number of atoms / RMM of compound

Question 22

How are mixtures separated

Answer 22

filtration
evaporation
chromatography
distillation

Question 23

distillation

Answer 23

used to separate mixtures of liquids that boil at different temperatures

Question 24

method of distillation

Answer 24

• solution is heated
• the liquid with the lowest boiling point will boil first and evaporate
• meaning it will be easier for the liquids to separate
• this all showing that it has a low boiling point

Question 25

chromatography

Answer 25

is used to separate a mixture of substances that have different solubilities

Question 26

how do you calculate the Rf value

Answer 26

distance travelled by ink / distance travelled by water

Question 27

how does the solubility of the ink effect chromatography

Answer 27

the more soluble the dye id the further it will travel up the paper

Question 28

what does the Rf value tell you about the chromatography paper

Answer 28

the bigger the Rf value, the further up the paper the ink has travelled the value will never be bigger than 1

Question 29

method of chromatography

Answer 29

- set up apparatus - on chromatography paper draw a line with pencil and a dot in the middle with an ink pemn - fold paper over wooden splint so the tip reaches water - take splint out and let it dry

Question 30

what colour would the chromatography paper be with an ink dot

Answer 30

blue and purple

Question 31

Separating mixtures with evaporation

Answer 31

heating the solution until the solvent evaporates and turns into gas leaving behind the solid residue

Question 32

filtration method

Answer 32

- crush the solid using a pestle and mortar -put solid into beaker and add 50cm3 of water and stir well - filter the mixture into a conical flask using a funnel and filter paper - once all collected put in evaporating basin - place over bunsen burner until all evaporated

Question 33

what are the changes that could happen in chemical reactions

Answer 33

- change colour - give off gas - get hot - get cold - give out light - make smells - form solids( precipitates)

Question 34

colour changes

Answer 34

A colour change might take place when two substances react. It can also happen when a compound is broken down by heating it

Question 35

effervescence

Answer 35

which a reaction in a liquid produces bubbles of gas

Question 36

precipitation

Answer 36

Some liquids react together to produce an insoluble solid. This is called a precipitation reaction and the solid formed is called a precipitate.

Question 37

temp change

Answer 37

Chemical reactions can take in energy or release energy, often in the form of heat. This causes a change in temperature.

Question 38

exothermic temp change

Answer 38

the reactants hold more energy than the products, so exothermic reactions release energy in the form of heat. Exothermic reactions can be identified by an increase in temperature.

Question 39

endothermic temp change

Answer 39

Endothermic actions take in heat. So endothermic reactions can be identified by a decrease in temperature.

Question 40

reactants

Answer 40

they are the starting substances

Question 41

products

Answer 41

the new substances formed in a reaction

Question 42

what is the first stage in a chemical reaction

Answer 42

bond between the atoms in the reactants are broken

Question 43

second stage of a chemical reaction

Answer 43

the atoms re-organise

Question 44

third stage of a chemical reaction

Answer 44

new bonds are made between the atoms in the products

Question 45

symbol equations

Answer 45

uses the formulae of the reactants and products to show what happens in a chemical reaction

Question 46

how do you calculate percentage yield

Answer 46

actual yield / theoretical yield X 100

Question 47

balanced equation

Answer 47

is where there is the same number of atoms of each element on each side of the equation

Question 48

what charge are group 1 metals

Answer 48

1+

Question 49

what charge are group 2 metals

Answer 49

2+

Question 50

what charge are group 6 elements

Answer 50

2-

Question 51

what charge are group 7 elements

Answer 51

1-

Question 52

what is 1 mole - avogadro constant

Answer 52

6 X 10,23

Question 53

the mass of 1 mole of an element

Answer 53

is the same as the atomic mass of the element

Question 54

the mass of 1 mole of a molecule

Answer 54

is the same as the molecular mass

Question 55

moles equation

Answer 55

mass / Ar or Mr

Question 56

mass equation

Answer 56

moles X Ar or Mr

Question 57

empitical formula

Answer 57

simplest formula of a compound