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Gcse Science Higher 💡 > Chemistry gcse paper 1 > Flashcards

Chemistry gcse paper 1 Flashcards

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1
Q

What do we use to measure atoms molecule and ions

A

We use moles as the actual masses are too small to be useful in calculations

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2
Q

One mole of a substance contains the same…….

A

Number of particle as one mole of any other substance

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3
Q

What is the Avogadro constant?

A

1 mole of a substance is the Avogadro number of particles of that substance

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4
Q

What is the Avogadro number?

A

6.02 x 10^23

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5
Q

Number of particles =

A

Avogadro x the amount of substance in a mol

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6
Q

Calculate the number of water molecule in 0.5 mol of water

A

6.02 x 10^23 x 0.5 = 3.01 x 10^23

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7
Q

Mass=

A

Relative formula mass x amount

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8
Q

Calculate the mass of 0.25 mol of carbon dioxide molecules ( Mr of co2=44)

A

44 x 0.25 = 11

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9
Q

How to calculate amounts in moles

A

Mass
Amount =———————————
relative atomic mass

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10
Q

What is a limiting reactant

A

The reactant used up first in a reaction

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11
Q

What does it mean when a product is in excess

A

The reactant left over when the limiting reactant is all used up

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12
Q

What is concentration measured in

A

G/ dm ^3. Or mol/dm^3

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13
Q

Concentration in mol/dm^3=

A

Amount of solute in mol
————————————
Volume in dm^3

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14
Q

In ionic bonds what do metal atoms and non metals atoms do

A

Metal atoms lost electrons to form positively charged ions

Non metal atoms gain electrons to form negatively charged ions

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15
Q

What is an ionic compound

A

A giant structure of ions

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16
Q

Why are lattices formed

A

The ions attract each other and form a regular pattern with positive charges ions next to each other

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17
Q

What is an ionic lattice held together by

A

Strong electrostatic forces of attraction between the positively charged ions

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18
Q

What is wrong with the 3D ionic lattice

A

It shows gaps which don’t actually exist

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19
Q

What does covalent bonding lead to

A

The formation of substances with different types of structures for example small molecules which contain a fixed number of atoms joined by covalent bonds
Giant covalent substances which contain many atoms joined by covalent bonds

20
Q

What’s an example of a giant covalent

A

Silicon dioxide graphite and diamond

21
Q

What are the properties of giant covalent structures

A

They have high melting points and boiling points this is because large amounts of energy are needed to overcome their sting covalent bonds to make them melt or boil. Most cannot conduct electricity as they have no charged particles free to move. Graphic a form of carbon however can conduct electricity.

22
Q

How many strong covalent bond does each carbon atoms form in graphite and diamond

A

Diamond- each carbon atom is joined to 4 other carbon atoms

Graphite- forms 3 covalent bonds with other carbon atoms

23
Q

Why does graphite conduct electricity

A

It has delocalised electrons like metals which can freely move between the layers in Graphite. Making graphite useful in batteries and electrolysis

24
Q

Why is graphite a good lubricant

A

The forces between layer in graphite are weak so they can slide over each other making graphite slippery

25
Q

What do titrations measure

A

The volume of acids and alkali solution that react with each other can be measure with titration using a suitable indicator

26
Q

What is a burette and a pipette

A

Burette is used to add small measured volumes of 1 reactant to another

Pipette are used to accurately measure volume of a reactant before transferring to conical flask

27
Q

What is the titre

A

The volume added (the difference between the end and start readings)

28
Q

What is electrolysis

A

It involves braking down electrolytes to form elements the products of electrolysis can be predicted for a given electrolyte

29
Q

What are electrolytes

A

Ionic compounds that are in the molten state ( heated to become liquids ) or dissolved in water

30
Q

What happens in electrolysis

A

Electrical energy from a direct current supply breaks down electrolytes the free moving ions in electrolytes are attracted to the oppositely charged electrodes which connect to the dc supply

31
Q

What is the positively charged electrode in electrolysis called

A

It is called the anode

32
Q

What is the negatively charged called

A

Cathode and it is where all the positive charge ions move towards the cathode

33
Q

What happens when ions reach an electrode

A

They gain or lose electrons as a result they form atoms or molecules or elements

34
Q

What happens to positive ions

A

They gain electrons from the negatively charged cathode

35
Q

What happens to the negative ions

A

They lose electrons at the positively charged anode

36
Q

What happens during the electrolysis of lead bromide pbBr2

A

Pb 2+ ions gain electrons at the cathode and become pb atoms

Br- ions lose electrons at the anode and become be atoms which pair up to form br2 molecules

Lead forms at negative electrode and bromine at positive

37
Q

What happens in the electrolysis of water acidified with dilute sukfuric acid

A

H+ ions are attracted to the cathode gain electrons and form hydrogen gas
OH- ions are attracted to the anode lose electrons and form oxygen gas

38
Q

What is a half equation used to represent in electrolysis

A

To show what happens at an electrode during electrolysis to shows what happens when ions gain or lose electrons

39
Q

Give examples of what happens at the cathode

A

Na+ + e- —>. Na

Pb2+. + 2e- —-> pb

2h+. + 2e- —-> H2

40
Q

Exothermic reactions

A

Transfer energy to surroundings and the temp of surrounds increases

41
Q

Endothermic

A

Take in energy and the temperate of surroundings decrease

42
Q

Exothermic reactions include

A

Combustion
Oxidation
Neutralisation

43
Q

Some endo thermic reactions include

A

Thermal decomposition

Citric acid and sodium hygeogencarbonate

44
Q

What happens to the energy level in an Exothermic reaction

A

The energy level decreases as energy is given out to the surroundings

Arrow goes down on graph

45
Q

What happens to the energy level I. An endothermic reaction

A

The energy level increases this is because energy is taken in from the surroundings

Arrow goes up on graph

Gcse Science Higher 💡 (3 decks)

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