Edexcel IGCSE Chemistry (Double award) in 562 flashcards

In which state of matter do particles have a very large amout of kinetic energy?

Gas

In which state of matter do particles have a very small amout of kinetic energy?

Solid

Explain why evaporating water does not produce H and O atoms.

Because the covalent bonds between H and O atoms do not break during boiling. Only the intermolecular forces between water molecules weaken.

Explain what happens to the particles in a gas when the gas expands.

They move further apart from one another.

Name the three changes of state during which particles absorb energy.

Melting, evaporation, sublimation

Name the three changes of state during which particles lose energy.

Freezing, condensation, deposition.

What does soluble mean?

Dissolves in water

What does insoluble mean?

Does not dissolve in water

Define solute

A solid that dissolves in a solvent

Define solvent

The liquid in which the solute dissolves to form a solution

Define saturated solution

A solution in which no more solute can dissolve at a given temperature

Is dissolving a physical change or a chemical reaction?

Physical change

What happens to particles when they dissolve?

The solute particles spread out and fit into the spaces between solvent particles.

Define diffusion

The movement of particles from an area of high concentration to an area of low concentration

Describe what happens after a drop of ink is placed in a glass of water

The colour will spread slowly through the water until the ink particles are evenly spread out.

Explain why diffusion is slower in liquids than in gases

Because the particles in a liquid move more slowly

Explain why diffusion does not happen in solids

Because the particle in a solid do not move from place to place

What happens to the solubility of a solid as you increase the temperature?

It increases

What happens to the solubility of a gas as you increase the temperature?

It decreases

Define atom

The smallest part of an element that can still be recognised as that element

Define element

A substance made of only one type of atom

Define compound

A substance made of two or more different atoms chemically bonded together in a fix ratio.

Define molecule

A substance made of more than one atom chemically bonded together (can be atoms of the same type!)

Define mixture

A substance made of more than one thing not chemically bonded together and not in a fixed ratio

Describe the melting point of pure substances

Fixed melting point

Describe the melting point of mixtures

Mixtures may melt or boil over a range of temperatures

Filtration

Used to seperate undissolved solid from a mixture of a solution

How could you obtain the salt from a salty water solution?

Filtration or Crystaltion can be used to isolate the salt from the solution

How could you obtain the water from a salty water solution?

Simple distillation

How could you separate a mixture of water and alcohol?

Fractional distillation

How could you separate a mixture of inks?

Paper chromatography

What is chromatography?

A process to separate a mixture

How can chromatography show the difference between pure and impure substances?

Pure ones will not separate into a number of spots

How is the Rf value calculated?

distance moved by spot/distance moved by solvent

What does a substance's Rf value depend on?

How soluble it is in the solvent

In chromatography, why must the substances be placed on a pencil line?

Pencil will not dissolve in the solvent

In chromatography why must the solvent height be lower than the pencil line?

So that the substances do not dissolve into the solvent off the paper

Define chromatogram

The results of separating mixtures by chromatography

What is fractional distillation?

A process used to separate mixtures of substances that have different boiling points

Define molecule

Two or more atoms joined by a chemical bond

State the three subatomic particles

Protons, neutrons, electrons

State the masses of the subatomic particles

Protons: 1, neutrons: 1, electrons: 0

State the relative charges of the subatomic particles

Protons: +1, neutrons: 0, electrons: -1

How are the subatomic particles arranged in an atom? (3 marks)

Protons and neutrons in the nucleus, electrons orbiting in shells

What is the atomic number of an atom?

The number of protons in an atom

What is the mass number of an atom?

The number of protons + the number of neutrons in an atom

How do you calculate the number of neutrons in an atom?

Mass number - atomic number

How are the electrons arranged in atoms?

Orbiting the nucleus in shells

How many electrons can go in the first shell?

2

How many electrons can go in the second and third shells?

8

How many electrons does a calcium atom have?

20

How many electrons does a silicon atom have?

14

How are the electrons in sulphur arranged?

2,8,6

How are the electrons in magnesium arranged?

2,8,2

How many electrons are in the outer shell of boron?

3

How many electrons are in the outer shell of phosphorous?

5

How many electrons are in the outer shell of sodium?

1

An element has three shells and three electrons in the outer shell. What element is it?

Aluminium (group 3, period 3)

How many electrons are in the outer shell of Gallium?

3

What are isotopes?

Atoms with the same number of protons but different numbers of neutrons.

Explain why atoms have no overall charge.

They have equal numbers of protons and electrons

Define relative atomic mass

The average mass of one atom of an element, relative to carbon-12

Why are relative atomic masses not whole numbers?

Because they are weighted averages of the masses of all the known isotopes of an element

Describe how to calculate relative atomic mass

(atomic mass1 x abundance1)+(atomic mass2 x abundance2) etc

What are groups in the periodic table?

The columns, numbered 1, 2, 3, 4, 5, 6, 7, 0

What are periods in the periodic table?

The rows in the periodic table

The elements in the periodic table are in order of...

... increasing atomic number

What can the group tell you about the electrons in an atom?

How many electrons in the outer shell. E.g. carbon is in group 4 so has 4 electrons in the outer shell

What can the period tell you about the electrons in an atom?

How many shells an atom has. E.g. carbon is in the second period so has two shells

An atom has four shells and two valence electrons. What element is it?

Calcium

How many valence electrons do the group3 elements have?

3

What is special about the outer shell of the group 0 elements?

They are full

How many electron shells do the period 2 elements have?

2

How many valence electrons do the group 7 elements have?

7

Metals are generally _________ (good/poor) electrical conductors and non-metals are generally _________ (good/poor) electrical conductors.

good, poor

Metal oxides are generally ________ (acidic/basic)

basic

Non-metal oxides are generally ________ (acidic/basic)

acidic

Describe how the acid-base character of the oxides period 3 elements changes as you move across the period.

basic to acidic

Explain why the group 1 elements are called alkali metals

They are metals that form alkalis when they react with water

Describe how the metallic and non-metallic character of the elements in period 3 changes as you go across the period.

metallic to non-metallic

What is the name given to the elements that have a mixture of metallic and non-metallic properties?

Metalloids (or semi-metals)

Why do the elements in the same group often have similar chemical properties?

They have the same number of valence electrons.

In terms of electrons, what do group 1 elements have in common?

1 electron in the outer shell

In terms of electrons, what do group 7 elements have in common?

7 electrons in the outer shell

In terms of electrons, what do group 0 elements have in common?

Full outer shell

What is more reactive, lithium or sodium?

Sodium

What is more reactive, chlorine or bromine?

Chlorine

Define inert

Unreactive

Explain why the noble gases are inert

They have full outer shells, so do not need to gain or lose electrons

What are reactants?

The substances involved in a chemical reaction

What are products?

The substances formed when reactants have a chemical reaction

Balance the equation: Li + H₂O → LiOH + H₂

2Li + 2H₂O → 2LiOH + H₂

Balance the equation: K + H₂O → KOH + H₂

2K + 2H₂O → 2KOH + H₂

What is the state symbol for solid?

(s)

Balance this equation: Mg + O₂ --> MgO

2Mg + O₂ --> 2MgO

Balance this equation: H₂SO₄ + Al₂O₃ --> H₂O + Al₂(SO₄)₃

3H₂SO₄ + Al₂O₃ --> 3H₂O + Al₂(SO₄)₃

What does the state symbol (l) stand for?

liquid

What does the state symbol (aq) stand for?

aqueous (dissolved in water)

What is the state symbol for gas?

(g)

What is Mr of magneisum

24