Chemistry mock

Question 1

What’s the difference between a pure substance and a mixture

Answer 1

A pure substance only contains one molecule whereas a mixture contains two or more pure substances

Question 2

How to use melting point information to decide whether a substance is pure or it is a mixture

Answer 2

A pure substance has a definitive boiling and melting point whereas a mixture has more than one boiling and melting point as it is made up of more than one compound

Question 3

What does it mean if a call and have has jagged lines

Answer 3

It is an impure substance

Question 4

Why does the temperature not change as a pure substance melts

Answer 4

The temperature does not change because the energy is used to change the state of the substance rather than being transferred into kinetic energy

Question 5

Name some mixtures that can be separated by filtration

Answer 5

Spaghetti and water

Insoluble solids from liquids

Question 6

Name some mixtures that can be seperated by crystallisation

Answer 6

Remove salt from sea water
Remove salt from rock salt

Used to separate soluble solid from a liquid

Question 7

How is simple distillation used and what is it for

Answer 7

For separating and liquid from a solid if you want to keep the liquid.

It is a two step process in which a liquid is heated and evaporated off and then go through a condenser ,which cold water is running around, in order to turn the gas into a liquid again.

Question 8

How do you calculate Rf value in chromatography

Answer 8

Distance travelled by a dye/distance travelled by solvent

Question 9

Why must water used in chemical analysis be pure

Answer 9

If it is not pure it will not boil at 100° exactly

Question 10

Describe how the size of an atom compares to the size of its nucleus

Answer 10

The nucleus of an atom is 1/100,000 of the size of the atom itself

Question 11

State the meaning of atomic number

Answer 11

The amount of protons in an atom (equal to the amount of electrons)

Question 12

State the meaning of mass number

Answer 12

How much it weighs

Question 13

How do you calculate the number of protons neutrons and electrons using atomic and mass numbers

Answer 13

Protons+neutrons=mass number

Protons=atomic number

Question 14

What’s an isotope

Answer 14

They have the same number of protons but different numbers of neutrons

Question 15

Explain why the relative atomic mass of many elements are not whole numbers

Answer 15

Because it is an average of the different isotopes within the element

Question 16

How did Mendeleev arrange elements in the periodic table

Answer 16

He ordered elements in relative atomic mass instead of atomic structure

Question 17

How did mendeleev predict existence of elements he hadn’t discovered yet

Answer 17

He was able to work out the atomic mass of the elements missing and so was able to predict their properties

Question 18

Recall the position of the metals and non metals in the periodic table

Answer 18

Non metals are in groups 1-8 and the non metals are in the middle

Question 19

What does the term electronic configuration mean

Answer 19

He amount and distribution of electrons in an atom

Question 20

How do you predict electronic configurations

Answer 20

Group number is no of electrons on outer shell

Period number is number of shells

Question 21

What happens to a metal during ionic bonding

Answer 21

It becomes positively charged because they all lose electrons

Question 22

What happens to a non metal when it ionicly bonds

Answer 22

It becomes negatively charged because it gains electrons.

The number of electrons it loses is 8-group number

Question 23

What keeps the ionic bonds together

Answer 23

Strong electrostatic forces of attraction between the opposite charges

Question 24

What is a cation and an anion in ionic bonding

Answer 24

A negatively charged ion is anion

A positive overall charge is a cation

Question 25

What is ionic bonding and what is an example

Answer 25

The swapping of electrons Sodium chloride

Question 26

What are the melting and boiling points of ions like

Answer 26

High melting and boiling points because strong electrostatic forces between oppositely charged ions are hard to break a lot of energy is needed

Question 27

Do ions conduct electricity

Answer 27

Ions don't conduct electricity unless molten (liquid) because when melted ions move freely about the structure

Question 28

Are ions soluble in water

Answer 28

Ions are soluble in water because h20 has a negative and positive positive end( polar molecule) that is attracted to both positive and negatively charged ions pulling the structure apart

Question 29

What does the ending ate mean of an ion

Answer 29

The 3 or more elements ionically bonded one of which is always oxygen

Question 30

What does and -ide ending mean

Answer 30

Only 2 elements covalently bonded

Question 31

What is a simple covalent bond

Answer 31

Small amounts of atoms joined together in individual molecules

Question 32

What is a giant covalent bond

Answer 32

Large networks of many covalent bonds

Question 33

What types of elements can be covalently bonded

Answer 33

Non metals

Question 34

Give an example of a simple and a giant covalent bond

Answer 34

Simple- water | Giant- diamond

Question 35

What is a covalent bond

Answer 35

The sharing of electrons

Question 36

Do simple and giant covalent bonds conduct electricity

Answer 36

No because there are no free electrons Except graphite- giant covalent bond

Question 37

Are simple and covalent bonds soluble in water

Answer 37

They are insoluble because water is a polar molecule that cannot attract neutral molecules

Question 38

What are simple covalents melting and boiling points like

Answer 38

Low melting and boiling points because of weak intermolecular forces

Question 39

Describe metallic bonding

Answer 39

Metal atom loses outer electrons to form positively charged ion Free electrons form a sea of delocalised electrons

Question 40

What is the structure of metallic bonding like

Answer 40

Good crystalline organised layers

Question 41

Do metals conduct electricity

Answer 41

Yes due to sea of free electrons

Question 42

Metals have what melting and boiling points

Answer 42

High melting and boiling points because of strong electrostatic forces of attraction

Question 43

Describe the structure of a metal

Answer 43

Postive ions and free sea of delocalised electrons

Question 44

How to calculate empirical formula

Answer 44

Mass of each element in question➗atomic mass Do the ratio Turn it into a formulae

Question 45

How to calculate masses of reactants and products

Answer 45

1) calculate mr of reactant and the product that you are asked about 2)decide whether you are being asked to find the mass of a reactant or a product 3) if reactant--- mr of reactant➗mr of product 4 if product---- mr of product➗mr of reactant 5) multiply by known mass

Question 46

Formula triangle for concentration of soloutions

Answer 46

Mass(g) on top Concentration(g/dm -3) x volume (dm3)

Question 47

What does avagasros constant show

Answer 47

The amount of atoms of one substance in a mole

Question 48

What is the moles formula triangle with mass in it

Answer 48

Mass on top Ar or Mr x moles

Question 49

What is the moles formula triangle for working out particles

Answer 49

Particles of top No of moles x avo. Constant