Chemistry Flashcards
Why does the structure of an element conduct electricity?
A It has delocalised electrons
B It contains hexagonal rings
C It has weak forces between the layers
D It has ionic bonds
A It has delocalised electrons ✔
B It contains hexagonal rings
C It has weak forces between the layers
D It has ionic bonds
Substance Boiling point
Water 100°C
Methane -162°C
Which statement explains the data in the table? [1 mark]
A Methane has a lower boiling point than water
B The intermolecular forces between the molecules in methane are weaker than the intermolecular forces between the molecules in water
C The covalent bonds between the atoms in a water molecule are stronger than the covalent bonds between the atoms in a methane molecule
D The covalent bonds between the atoms in a water molecule are weaker than the covalent bonds between the atoms in a methane molecule
A Methane has a lower boiling point than water
B The intermolecular forces between the molecules in methane are weaker than the intermolecular forces between the molecules in water ✔
C The covalent bonds between the atoms in a water molecule are stronger than the covalent bonds between the atoms in a methane molecule
D The covalent bonds between the atoms in a water molecule are weaker than the covalent bonds between the atoms in a methane molecule
Which statement describes a limitation of the particle model?
[1 mark]
A In the model particles in a solid vibrate about fixed positions
B In the model particles in a liquid are close together
C In the model particles in liquids and gases have random arrangements
D In the model there are no forces between particles
A In the model particles in a solid vibrate about fixed positions
B In the model particles in a liquid are close together
C In the model particles in liquids and gases have random arrangements
D In the model there are no forces between particles ✔
Draw the structure of:
- a gas
- a iquid
- a solid metal
- an ionic substance
List 2 characteristics of ionic compounds
Ionic compounds have high melting points and
ionic compounds conduct electricity when dissolved in water.
Metals are good conductors of electricity because they contain electrons that are ______________ .
Weak
Delocalised
Strong
Small
Covalent
Ionic
Metals are good conductors of electricity because they contain electrons that are delocalised.
Metals have high melting points because their bonding is ________ .
Weak
Delocalised
Strong
Small
Covalent
Ionic
Metals have high melting points because their bonding is strong.
Give TWO advantages of using nanoparticles in sun creams.
[2 marks]
TWO advantages of using nanoparticles in sun creams.
1, nanoparticles provide better coverage
2. nanoparticles give more protection from the Sun’s ultraviolet rays
What reasons would an alloy be stronger than the pure metal of its component [2 marks]
The atoms are different sizes. [1]
Therefore there are no layers to slide over each other. [1]
Explain how a covalent bond holds two atoms together [2 marks]
There is an electrostatic force of attraction between a shared pair of negatively charged electrons [1] and two positively charged nuclei. [1]
Explain, in terms of its structure, why graphite can be used as a lubricant.
[3 marks]
- The carbon atoms in graphite are arranged in layers. [1]
- There are only weak intermolecular forces between the layers. [1]
- The layers can slide over each other. [1]
A coarse particle has a diameter of 1 × 10-6 m.
A nanoparticle has a diameter of 1.6 × 10-9 m.
Calculate how many times bigger the diameter of the coarse particle is than the diameter of the nanoparticle.
[2 marks]
1 ÷ 1.6 = 0.625
and use of indices 10-6 ÷ 10-9 = 103 = 1000 [1]
0.625 × 1000 = 625 times bigger. [1]
Some types of solder are alloys of tin and lead.
Some solder was made by mixing 22.5 g of lead with 15.0 g of tin.
Calculate the percentage of tin in this solder.
[2 marks]
Percentage of tin
15.0g / (15.0+22.5)g
× 100 [1]
= 40.0% [1]
A nanoparticle has a cubic shape. The length of its sides is 4 nm.
Calculate the surface area to volume ratio for the nanoparticle.
[3 marks]
Surface area = 6 × 4 nm × 4 nm
= 96 nm2 [1]
Volume = (4 nm)3 = 64 nm3
Surface area : volume ratio = 96 : 64 [1]
= 1.5 [1]
Name one piece of apparatus suitable for measuring the boiling point of a liquid.
[1 mark]
A thermometer / temperature probe. [1]
Give two reasons why hazard symbols are used on containers in the laboratory.
[2 marks]
To indicate the dangers associated with the contents. [1]
To inform people about precautions to take when using these substances in the laboratory. [1]
Complete the table below.
Hazard: Electricity supply
Possible harm : _____________________
Possible precaution: _____________________
Hazard: Electricity supply
Possible harm : Electric shock
Possible precaution: Switch off before handling apparatus
Complete the table:
Hazard: Copper sulfate
Possible harm : Causes skin irritation
Possible precaution: _____________________
Hazard: Copper sulfate
Possible harm : Causes skin irritation
Possible precaution: Avoid getting on skin/wear gloves
A student uses a temperature probe to measure the melting points of three substances.
His results are in table 1.
Table 1
Substance Melting point
X 31.2°C
Y 16.9°C
Z 88.1°C
What is the resolution of the temperature probe?
[1 mark]
0.1°C (number and unit required for the mark) [1]
Describe the arrangement and movement of particles in solids
- The particles in solids are close together and regularly arranged.
- The particles in solids vibrate about fixed positions.
Describe the arrangement and movement of particles in liquids
- The particles in liquids are close together and randomly arranged
- The particles in liquids move around each other
Describe the arrangement and movement of particles in gases
The particles in gases are far apart and are randomly arranged
Explain TWO things that happen to the particles in a liquid during boiling.
- during boiling, energy is transferred to particles
- bonds/forces of attraction between particles break / are overcome.
Explain 2 key properities of solids
Solids:
1/ have a fixed shape and cannot flow, because their particles cannot move from place to place.
2. cannot be compressed (squashed), because their particles are close together and have no space to move into.
Explain 2 key properities of liquids
Liquids:
1. flow and take the shape of their container, because their particles can move around each other
2. cannot be compressed, because their particles are close together and have no space to move into
Explain 2 key properities of gases
Gases:
1. flow and completely fill their container, because their particles can move quickly in all directions
2. can be compressed, because their particles are far apart and have space to move into
Some substances can change directly from solid to gas, or from gas to solid, without becoming a liquid in between.
- What is this process called?
- Give one example.
- This is called sublimation. S
- Example - solid carbon dioxide (‘dry ice’) and iodine can sublime.
Fill in the blanks:
_____________ must be transferred, by _____________, to a substance for changes of ___________ to happem
Energy must be transferred, by heating, to a substance for changes of state to happen.
Every substance has its own ___________ point and ___________ point.
Every substance has its own melting point and boiling point.
The _____________ the forces between particles, the ______________ its melting and boiling points.
The stronger the forces between particles, the higher its melting and boiling points.
The forces between ions in an ionic solid are ___________han those between molecules in water or hydrogen.
(stronger/ weaker)
The forces between ions in an ionic solid are stronger than those between molecules in water or hydrogen.
The amount of _________needed to change ___________from solid to liquid, and from liquid to gas, depends on the __________of the forces between the particles of a substance.
The __________ the forces of attraction, the ____________energy is required
The amount of energy needed to change state from solid to liquid, and from liquid to gas, depends on the strength of the forces between the particles of a substance. The stronger the forces of attraction, the more energy is required
Change of state: Melting
During these changes the particles gain ________ which is used to ________some of the_______between particles
(overcome,/ join / break / bind / boiling / energy / escape)
During these changes the particles gain energy, which is used to:
break some of the bonds between particles during melting
During evaporating or boiling. the particles _______ energy, which is used to
_________the remaining forces of _____________between particles/
(lose / gain / overcome,/ join / break / energy / escape
repulsion / attraction )
During evaporating or boiling. the particles gain energy, which is used to overcome the remaining forces of attraction between particles.
Whats the difference in particle movement between evaporation and boiling ?
In evaporation, particles leave a liquid from its surface only.
In boiling, bubbles of gas form throughout the liquid. They rise to the surface and escape to the surroundings, forming a gas.
Evaporation can take place ________ the boiling point of a substance.
(above / below)
Evaporation can take place below the boiling point of a substance.
Energy is transferred from a substance to the surroundings when a substance __________ or _______________ . This is because the forces of__________ between the particles get _____________.
Condensing and freezing
Energy is transferred from a substance to the surroundings when a substance condenses or freezes. This is because the forces of attraction between the particles get stronger.
The state of a substance at a given________________ can be predicted if its ___________ point and _____________point are known
The state of a substance at a given temperature can be predicted if its melting point and boiling point are known
What is the predicted state?
Given temperature < melting point
Temperature Predicted state
Given temperature < melting point = Solid
What is the predicted state?
Given temperature is between melting and boiling points
Given temperature is between melting and boiling points= Liquid
What is the predicted state?
Given temperature > boiling point
Given temperature > boiling point = Gas
he melting point of oxygen is -218°C and its boiling point is -183°C. Predict the state of oxygen at -200°C.
Oxygen will be in the liquid state at -200°C (because this is between its melting and boiling points).
List 2 limitations of the particle model
The particle model assumes that particles are solid spheres with no forces between them. However:____________
Limitations of the particle model
The particle model assumes that particles are solid spheres with no forces between them. However:
- particles are not solid, since atoms are mostly empty space
- many particles are not spherical
What is an ion?
An ion is an atom or group of atoms with a positive or negative charge. I
How are ions formed?
Any of the explaations below:
1. Ions are formed by the transfer of electrons.
2. Ions form when atoms lose or gain electrons to obtain a full outer shell:
What happens to an atom to form an ion?
Ions form when atoms lose or gain electrons to obtain a full outer shell:
1. When metal atoms lose electrons to form positively charged ions
2. When non-metal atoms gain electrons to form negatively charged ions
How are positive metal ions formed?
Metal atoms lose electrons from their outer shell when they form ions:
- the ions are positive, because they have more protons than electrons
- the ions formed have full outer shells
- the ions have the electronic structure of a noble gas (group 0 element), with a full outer shell
Forming positive ions
For elements in groups 1, 2 and 3, the number of __________ lost is the _______ as the group number.
For elements in groups 1, 2 and 3, the number of electrons lost is the same as the group number.
How are negative ions formed?
The outer shells of non-metal atoms gain electrons when they form ions:
- the ions formed are negative, because they have more electrons than protons
- the ions have the electronic structure of a noble gas (group 0 element), with a full outer shell
For elements in groups 6 and 7, the __________on the ion is equal to (___ minus group number).
For elements in groups 6 and 7, the charge on the ion is equal to (8 minus group number).
Sulfur is in group 6 of the periodic table. What is the charge on its ions, and is the charge positive or negative?
The charge is negative, since sulfur is a non-metal. The charge on the ion is (8 - 6) = 2.
Iodine is in group 7. What is the charge on its ions, and is the charge positive or negative?
The charge is negative, since iodine is a non-metal. The charge on the ion is (8 - 7) = 1.
Small molecules:
What is a covalent bond?
A covalent bond is a shared pair of electrons.
Covalent bonding forms ____________
Covalent bonding forms molecules
Substances with small molecules have (high / low) melting points and (high / low) boiling points, and ( do/ do not) conduct electricity.
Substances with small molecules have low melting points and low boiling points, and do not conduct electricity.
How is a covalent bond formed?
A covalent bond is formed when two atoms share a pair of electrons.
Covalent bonding occurs in most _________elements,
Covalent bonding occurs in ______________ formed between _____________
Covalent bonding occurs in most non-metal elements, and
Covalent bonding occurs in compounds formed between non-metals.
Covalent bonds:
These ________ pair of _________ are found in the _______shells of the atoms. Usually each atom contributes one _____________to the shared pair of ________.
Covalent bonds:
These shared pair of electrons are found in the outer shells of the atoms. Usually each atom contributes one electron to the shared pair of electrons.
Most covalently bonded substances consist of small ________________
Most covalently bonded substances consist of small molecules.
What is a molecule?
A molecule is a group of two or more atoms joined together by covalent bonds.
Molecules of the same element or compound always contain the same number of _________of each element.
Molecules of the same element or compound always contain the same number of atoms of each element.
What equipment can be used to see atoms or molecules?
Some electron microscopes can produce images of atoms and simple molecules.
The atoms in a molecule are always joined together by a __________ _______
The atoms in a molecule are always joined together by a covalent bond.
Substances that are made up of ______do not form molecules.
Substances that are made up of ions do not form molecules.
Formulae of substances with simple molecules
The chemical formula of a substance with small molecules shows the number of __________ of each ____________ in one molecule of the substance.
Formulae of substances with simple molecules
The chemical formula of a substance with small molecules shows the number of atoms of each element in one molecule of the substance.
What are the number of atoms in water?
Water H2O Two hydrogen atoms and one oxygen atom
What are the number of atoms in Oxygen?
O2 Two oxygen atoms
State the number of atoms of each type in one molecule of methane, CH4.
A methane molecule is made up of one atom of carbon and four atoms of hydrogen.
State the number and type of atoms in one molecule of chlorine, Cl2.
A chlorine molecule is made up of two chlorine atoms.
Describe structure of giant covalent substances
Giant covalent substances have many atoms joined together by covalent bonds.
Give 3 examples of forms of Carbon with different giant covalent structures
Diamond, graphite and graphene are forms of carbon with different giant covalent structures.
Covalent bonding leads to the formation of substances with different types of structures, for example:
- small molecules, which contain a _____ number of atoms joined by _____ _____
- _____ _covalent substances, which contain many ______ joined by covalent bonds
Substances with many covalent bonds:
Covalent bonding leads to 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
Give an example of a substance with a giant covalent structure.
An example - Silicon dioxide
Silicon dioxide (often called silica) is the main compound found in sand. It is an example of a substance with a giant covalent structure. It contains many silicon and oxygen atoms. All the atoms in its structure are linked to each other by strong covalent bonds. The atoms are joined to each other in a regular arrangement, forming a giant covalent structure. There is no set number of atoms joined together in this type of structure.
Substances with giant covalent structures are _______at room temperature
Substances with giant covalent structures are solids at room temperature.
Substances with giant covalent structures have very (low / high) melting points and boiling points.
Substances with giant covalent structures are solids at room temperature. They have very high melting points and boiling points.
What does havimg a high melting point and boiling point mean?
Very high melting points and boiling points means large amounts of energy are needed to overcome their strong covalent bonds to make them melt or boil.
Gant covalent structures are (good / bad) conductors of electricity
Most substances with giant covalent structures have no charged particles that are free to move. This means that most cannot conduct electricity.
Wju are most giant covalent structures poor conductors?
Most substances with giant covalent structures have no charged particles that are free to move.
State three properties that are typical of substances with giant covalent structures.
They have high boiling points, high melting points and they cannot conduct electricity.
Explain why diamond does not conduct electricity and why graphite does conduct electricity.
Diamond does not conduct electricity because it has no charged particles that are free to move. Graphite does conduct electricity because it has delocalised electrons which move between the layers.
