C5 Flashcards

Question	Answer
Dry air contains non-metal elements in large amounts. Name some examples.	Nitrogen, Oxygen, Argon.
Dry air also consists of non-metal elements in small amounts. Name some examples.	Carbon dioxide and water vapour.
What is meant when molecules are held together by COVALENT bonds?	It means that the atoms in the molecules share a pair of electrons.
Why are the atoms held together?	The positively charged nuclei of both atoms are attracted to the negatively charged pair of electrons.
Why are the melting and boiling points of simple molecular substances low?	The attractive forces between small molecules are very weak. Very little energy is required to break the attractive forces between them and move them apart.
Why can't pure molecular substances conduct electricity?	Molecules of elements and compounds have no overall electrical charge.
What is strong and weak in small covalent molecules?	In small covalent molecules, forces between molecules are weak, but forces within covalent bonds are strong.
What happens when molecular substances melt?	Molecules are easily separated from one another, but the molecules themselves are not broken up into separate atoms.
What is the hydrosphere?	The hydrosphere is all the water on Earth, including oceans, seas, lakes and rivers.
What does the hydrosphere contain?	The hydrosphere is mostly water, with some dissolved compunds called salts.
What happens when water evaporates?	When water evaporates, dissolved salts form solid crystals.
Salts are ionic compounds. What are ions?	Ions have either a positve or a negative charge and are arranged in a giant 3-D pattern called a lattice.
What is an ionic bond?	An ionic bond is the strong force of attraction between positively and negatively charged ions.
Why do ionic compounds have high melting and boiling points?	A large amount of energy is needed to overcome the forces between ions in the lattice. The forces of attraction between the ions is great.
Why can't ions conduct electricity when solid?	When solid, the ions are not free to move. When they are melted, or dissolved in water, the ions can move and conduct electricity.
What is a molecular ion?	Some ions, e.g the sulfate ion SO4^2- contain groups of atoms.
How can ions be identified in a compound?	•They can be identified by their distinctive properties, e.g compounds containing the copper ion are often blue. •Solutions of some ionic compounds make precipitates of an insoluble compound when mixed. The colour of the precipitate is used to identify the ion in the compound
What is the effect of adding an alkali, such as dilute sodium hydroxide, to different positive metal ions?	It gives different colours of precipitate, which can then be used to identify the ions in the compound.
How can negative carbonate ions be identified?	You add dilute acid and look for fizzing (effervescence). This is because carbonates fizz when an acid is added because carbon dioxide gas is made in the reaction.
How can negative chloride, bromide and iodide ions be identified?	By adding dilute silver nitrate or dilute barium chloride and looking for precipitates.
Precipitates form when an insoluble solid is made in the reaction. Give an example of this.	Most metal hydroxides are insoluble, as is silver chloride from the reaction of silver ions and chloride ions.
What is the lithosphere?	The lithosphere is the rigid outer lauer of the Earth, made up of the crusy and the upper mantle.
What is found in the lithosphere?	It contains rocks and minerals.
What are minerals?	Minerals are solids with atoms or ions arranged in a regular arrangement/lattice. An example of this is carbon in the form of diamond or graphite.
Give examples of abundant elements that can be found in the Earth's lithosphere.	Silicon, oxygen and aluminium are very abundant elements in the Earth's lithosphere.
What are ores?	Ores are rocks that contain metal minerals. Some ores contain metal oxides.
How can copper, zinc and iron be extracted from their ores?	By heating their metal oxides with carbon, they can be extracted from their ores. Carbon reduces the metal oxide by taking away the oxygen.
What is a redox reaction?	A redox reaction is the extraction of metals by heating their oxides with carbon, because both oxidation and reduction happen.
Why does reduction occur in the extraction of some metals?	Reduction happens because the metal oxide loses oxygen.
Why does oxidation occur in the extraction of some metals?	The carbon gains the oxygen when a metal oxide reacts with carbon.
What is the balanced symbol equation for the reaction between zinc oxide and carbon?	2ZnO (s) + C (s) --> 2Zn (s) + CO2 (g)
Diamond and graphite contain many carbon atoms covalently bonded together in a regular lattice, what kind of structure is this called?	It is called a a giant covalent structure.
What are the physical properties of diamond?	The bonds in diamond are very strong and need a large amount of energy to break them. This means that diamond has very high melting and boiling points, so it cannot dissolve in water. It does not contain any charged particles so it cannot conduct electricity when solid or molten.
Why are the properties of silicon dioxide similar to diamond?	Silicon dioxide also has a giant covalent structure.
Describe the structure of diamond.	In diamond, each carbon atom is covalently bonded to four other atoms in a tetrahedral lattice.
Describe the structure of graphite.	In graphite, each atom is strongly bonded to three others in sheets. The sheets are strong but there is only a weak force of attraction betwwen the layers, so they can slide over each other.
Why can graphite conduct electricity whereas diamond cannot?	Graphite can conduct electricity because of the delocalised (free) electrons in its structure. These arise because each carbon atom is only bonded to 3 other carbon atoms. However, in diamond, all 4 outer electrons on each carbon atom are used in covalent bonding, so there are no delocalised electrons.
What is the equation the find the percentafe of a metal in a mineral?	Percentage of metal in mineral = total mass of metal atoms / gram formula mass x 100
What is electrolysis?	Electrolysis is the passing of an electric current through an ionic compound when it is either molten or dissolved.
What is the name given to the compound that is dissolved in the water?	It is called the electrolyte because it has the ability to construct electricity.
What happens to the electrolyte as electricity passes through the solution?	It breaks down/ decomposes.
Give an example of a metal that is extracted from its ore through electrolysis.	Aluminium is extracted from aluminium oxide through electrolysis. Aluminium and oxygen are the products formed from this.
Why can't all metals be extracted from its ore by heating it with carbon?	Electrolysis is used to extract more reactive metals, such as aluminium, because their oxides cannot be reduced using carbon.
In electrolysis, what happens at the cathode and anode and why?	At the cathode, metals form, because the positive metal ions are attracted to the negatively charged electrode. At the anode, negative ions, such as Cl- and O2- move to the positively charged electrode, therefore forming non metals, such as oxygen and oxygen.
Why are metals useful?	They are strong, malleable, have high melting points, and are good conductors of electricity.
What holds together the atoms in metals?	They are held together by metallic bonds. The atoms are arranged in a regular pattern in a giant lattice.
What are the properties of metallic bonds?	They are strong, so a lot of energy is needed to melt or reshape them.
Describe where the term 'sea of electrons' comes from.	Metal atoms lose their outer shell electrons to form positive ions. In solid metals, the outer-shell electrons form a 'sea of electrons', which can move freely.
What are the properties of attractions in a metal?	The attraction between the positive ions and the sea of electrons is very strong, so that metals have high melting points and high strength.
Why are pure metals malleable?	All the atoms are the same size and can roll over each other, meaning that they can be reshaped even though the bonds are strong.
Give examples of metals that are poisonous.	Lead, mercury, and cadmium.
What can be destroyed due to poisonous metals?	It can destroy habitats, damage soil as well as water sources.
What are the disadvantages of the process of extracting metals?	•Extracting metals makes pollutant gases that cause acid rain (acid rain damages buildings, and makes water sources, like ponds, lakes slightly acidic.) •Large amounts of waste rock need to be processed to produce very small amounts of metal. •Processing large amounts of rock uses a lot of energy.
What can copper be used for?	Electrical wiring and circuits, pipes and building materials.
What metal was used before to make batteries for vehicles? What metal is used now to do this?	Lead was used before to make batteries, but it has now been replaced with lithium, as lead is toxic. Although lithium is not toxic, it is difficult to extract sufficient lithium needed for car batteries.

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