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Science👩‍🔬 > Chem fc 🧪(combined) > Flashcards

Chem fc 🧪(combined) Flashcards

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1
Q

Define atom

A

The smallest part of an element that Dan exist

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2
Q

Define compound

A

2 or more elements chemically combined

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3
Q

Define mixture

A

2 or more elements not chemically combined

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4
Q

Name 5 methods of separating mixtures

A

Filtration, crystallisation, simple distillation, fractional distillation, chromatography

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5
Q

Describe the plum pudding model of the atom

A

Theatre is a ball of positive charge with negative electrons embedded in it

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6
Q

Describe the method that led to the new model of the atom

A

The alpha particle scattering experiment. Most particles went straight through = empty space. Some deflected a little = positive centre. Some deflected back= large mass at cente

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7
Q

Compare the plum pudding model to the nuclear model of the atom

A

Both have positive charge( pp in a ball, nuclear in nucleus as protons). Both have electrons( pp randomly spread, nuclear in shells). Nuclear has a nucleus and neutrons

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8
Q

Why are atoms in the same group similar

A

They have the same number of electrons in their outer shell

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9
Q

Who is responsible for the modern periodic tablw

A

Dimitri mendeleev

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10
Q

What was mendeleev’s key innovation in making this table

A

He left gaps for undiscovered elements and changed the order in some places based on weights

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11
Q

What charged ion do metal atoms form

A

All positive ions

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12
Q

Describe group zero elements

A

Known as the noble gases are unreactive and have a full out of show

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13
Q

Describe the Trend shown by group one elements

A

Reactivity increases down the group

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14
Q

Describe the trends shown by group 7 elements

A

Reactivity decreases as you go down the group

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15
Q

How does group number relate to the charge of an ion for elements in each group?

A

Group one equals +1, group two equals +2, group three equals +3, group 6 equals 2- group seven equals 1-

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16
Q

Name the forces that hold ionic compounds together

A

Strong electrostatic forces

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17
Q

Name 3 giant covalent structures and two very large covalent structures

A

Giant = diamond, graphite, silicon dioxide
Very large = carbon nanotubes , buckminsterfullerene

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18
Q

Describe the bonding in metals

A

Positive metal ions, in neat rows, surrounded by a sea of delocalised electrons, held together by strong electrostatic forces

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19
Q

Name the changes of state as you increase temperature

A

Melting, boiling

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20
Q

Name the changes of state as you decrease temperature

A

Condensation, freezing

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21
Q

What are the limitations of the particle model?

A

All particles are represented as solid spheres. All particles are shown the same size. There are no forces shown. It is two dimensional.

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22
Q

How are the 4 states of matter represented in chemical equations?

A

Solid: (s) Liquid:(l) Gas: (g) Aqueous: (aq)

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23
Q

In 3 sentences, explain the melting point of ionic compounds

A

Strong electrostatic forces between oppositely charged ions. Forces act in all directions in the lattice. A lot of energy needed to overcome so it has a high melting point.

24
Q

In what state do ionic substances conduct electricity, why?

A

Molton and aqueous, as the ions are free to move and carry charge

25
Q

Do covalent molecules conduct electricity? Why?

A

No, there are no charged particles

26
Q

In three sentences, explain the boiling point of simple covalent compounds

A

Made up of small molecules. Have weakened intermolecular forces. Little energy needed to overcome so have a low boiling point.

27
Q

Why are polymers solid at room temperature?

A

Intermolecular forces between polymer molecules are relatively strong. A lot of energy is needed to overcome these forces

28
Q

In 3 sentences, explain the melting point of diamond and graphite

A

Giant covalent structure. Has strong covalent bonds. A lot of energy needed to break these bonds so they have a very high melting point.

29
Q

Give 3 examples of giant covalent structures

A

Diamond graphite silicon dioxide

30
Q

Explain why metal Alloys are harder than pure metals

A

Pure metals have layers which can slide so they are soft. Alloys have different sized atoms which distort the layers so they cannot slide and so they are harder.

31
Q

Why are metals good conductors?

A

A sea of delocalised electrons in the Metal carry charge through the metal

32
Q

Why can graphite conduct electricity

A

Delocalised electrons carry charge through the structure

33
Q

State the law of conservation of mass

A

No atoms are lost of made during a chemical reaction so the mass of products equals the mass of reactants

34
Q

How would you calculate relative formula mass

A

Sum of the relative atomic masses of the atoms in the numbers shown in the formula

35
Q

What is a MOLE

A

The mess of 1 mole is the relative formula mass in grams. It is made up of 6x1023 particles

36
Q

What is meant by limiting reactant

A

The reactant that is completely used up in a chemical reaction

37
Q

Define reduction and oxidation

A

Oxidation is gain of oxygen and loss of electrons while reduction is loss of oxygen and gain of electrons

38
Q

Write an equation to describe the reaction of potassium with water

A

Potassium + water —> salt + hydrogen

39
Q

Why is gold found in its pure form but iron is not

A

Iron is more reactive than gold so reacts with oxygen in the air to form iron oxide. Gold is unreactive.

40
Q

Which element is used to extract a metal from its oxide

A

Carbon

41
Q

Which ions make acids and alkalis

A

Acid- H+ ions
Alkalis - OH- ions

42
Q

Name 3 acids used in the science lab

A

Hydrochloric acid, sulphuric acid and nitric acid

43
Q

Name the types of salts produced by each acid

A

Hydrochloric- chloride salts sulphuric- sulphate salts nitric- nitrate salts

44
Q

Describe how a solid salt can be prefixed from a solution of that salt

A

Crystallisation- heat the solution to evaporate half the water, leave to cool and crystallise, scrape crystals from the surface and pat dry

45
Q

Describe how you can determine the pH of a solution

A

Universal indicator, pH probe

45
Q

Stir and ion equation for neutralisation

A

H+ + OH- —> H20

46
Q

Give the reason why some acids are strong and some are weak

A

Strong acids completely ionise. Weak acids only partially ionise.

47
Q

How are pH and acid strength related

A

As pH decreases by one unit, the concentration of hydrogen ions increases by a factor of 10

48
Q

Name the electrodes in electrolysis

A

Cathode and anode

49
Q

Why so solid ionic substances not conduct electricity

A

The ions are fixed in position and not free to move

50
Q

What is mixed with aluminium oxide in the industrial production of aluminium?

A

Cryolite

51
Q

What is the reason for mixing cryolite in with aluminium oxide

A

Reduces the melting point therefore saving energy

52
Q

Why might hydrogen be produced at the cathode

A

Water is also present so solution will contain H+ and OH- ions. Hydrogen will be released if it’s the least reactive of the metal and H+ ion

53
Q

Define exothermic

A

A reaction that transfers energy to the surroundings

54
Q

Define endothermic

A

Reaction that takes in energy from the surroundings

55
Q

Define activation energy

A

The minimum energy that particles must have to react

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