Elements, compounds and mixtures

Question 1

What is relative atomic mass

Answer 1

The mass of an atom compared to the mass of a Carbon 12 atom / 12

Question 2

What does chemical formula tell you

Answer 2

How much atoms of each elements there are in a unit of substance eg H2O

Question 3

What is relative formula mass

Answer 3

Total relative atomic mass of a chemical formula

Question 4

What is an empirical formula

Answer 4

The simplest whole number ratio of the atoms of each element in a compound

Question 5

Define purity

Answer 5

A substance consisting of just one element or compound

Question 6

How can you determine melting point and from that purity

Answer 6

Heat a substance slowly and stir, then compare this to that of a pure substance

Question 7

How does filtration work

Answer 7

Separates an insoluble solid form a liquid substance as the solid molecules are unable to pass through the filter paper

Question 8

How does crystallisation work

Answer 8

Saturate the solution and slowly evaporate it until crystals form

Question 9

Describe simple distillation

Answer 9

Separates solvent from solution, involves boiling the solvent which is then condensed by a condenser. This relies on the solvent having a much lower boiling point than the solute

Question 10

How does fractional distillation vary from simple distillation

Answer 10

Separates 2 or more substances from a mixture in the liquid state, using a fractional column

Question 11

How does chromatography work

Answer 11

Relies on a stationary and mobile phase

Question 12

Explain thin layer chromatography

Answer 12

-Put the solvent in a chromatography tank
-Add a small amount of sample to the base line of the silica or ammonia coated plate
-Let the solvent travel through and remove plate before it reaches the top
-Analyse the pattern

Question 13

How does gas chromatography work

Answer 13

The sample is turned into the gas state when injected. The carrier gas pushes the sample through, each component taking different times to travel and leave the column which the detector sends to the chromatogram.

Question 14

What are the chemical properties of metals and non metals

Answer 14

metals make positive ions, non-metal negative
Metals dont react with eachother, non-metals make compounds
Metal oxides are alkaline non-metal acidic

Question 15

What is a polymer

Answer 15

A molecule made of many smaller molecules called monomers

Question 16

What are monomers

Answer 16

simple molecules made from covalently bonded non metals

Question 17

What are metallic bonds like

Answer 17

Positively charged metal ions are attracted to delocalised electrons

Question 18

What did Mendeleev do

Answer 18

Mendeleev’s table included atomic weights of known elements, knowledge of their chemical reactions and their physical properties.Mendeleev also predicted elements.

Question 19

What are the patterns of chemical properties in the periodic table

Answer 19

-Elements arranged in order of increasing atomic number
-The electronic structure determines chemical properties

Question 20

What is diamond like

Answer 20

Exists as a giant covalent structure
Each carbon bonded to 4 others
High melting point hard and insulator

Question 21

What is graphite like

Answer 21

Giant covalent structure
Each carbon bonded to 3 others
Conductor
High melting point
Slippery

Question 22

What is graphene like

Answer 22

A single layer of graphene
Slippery
Extremely strong
Conductor

Question 23

What are fullerenes like

Answer 23

Eg nanotubes or bucky balls
Used as lubricants ect

Question 24

What happens when a substance changes state

Answer 24

Some or all bonds between particles break when melting or boiling, bonds form when condensing or freezing

Question 25

How big are nanoparticles

Answer 25

1-100nm

Question 26

Why are nanoparticles useful

Answer 26

-Small size useful for paints and cosmetics
-Large SA:Volume ratio useful as catalysts

Question 27

What are the risks of nanoparticles

Answer 27

Can absorb through skin, can be inhaled or pass into cells