1. Traces of a liquid were discovered in a bottle believed to contain perfume belonging to Queen Hatshepsut, ruler of
Egypt over 3500 years ago. Perfumes were made by dissolving plant extracts containing pleasant smelling terpenes
and esters in an edible oil. A little ethanol and water may also have been added.
Using your knowledge of chemistry, comment on the possible smell(s) when such a bottle is opened after being
stored for thousands of years.
2. Cooking involves many chemical reactions. Proteins, fats, oils and esters are some examples of compounds found
in food. A chemist suggested that cooking food could change compounds from being fat-soluble to water-soluble.
Use your knowledge of chemistry to comment on the accuracy of this
3. Blocked drains can be very unpleasant. Common causes of blocked drains in homes are fats, hair and food waste.
Using your knowledge of chemistry, comment on chemical methods that might be used to unblock drains
4 Desirable characteristics for a supermarket ready meal are that it
Has good flavour
Retains it’s appearance and texture
Has a long shelf life
Using your knowledge of chemistry, comment on how manufacturer’s achieve these characteristics.
5. The periodic table is an arrangement of all the known elements in order of increasing atomic number. The reason
why elements are arranged as they are in the periodic table is to fit them all, with their widely diverse physical and
chemical properties into a logical pattern.
Periodicity is the name given to regularly occurring similarities in the physical and chemical properties of the
Some Groups exhibit similarity between their elements such as group 1 and in other groups the elements are less
similar to each other such as group 4 , but each group has a common set of characteristics.
Adapted from RSC Visual elements,
Using your knowledge of chemistry, comment on similarities and differences in the patterns of physical and
chemical properties of elements in both group 1 and group 4.
6. Hydrogen peroxide is used in gels to whiten teeth. The ion –electron equation for the oxidation of
hydrogen peroxide is:
H 2 O 2 → O 2 + 2H + + 2e −
Using your knowledge of chemistry, comment on possible methods for measuring and comparing the
concentration of hydrogen peroxide present in two different gels.
7. Aspirin is a widely used medicine. It is advised that it is stored in dry, cool conditions.
Using your knowledge of chemistry, comment on the reasons why aspirin should be stored under
these conditions.
8. The Periodic Table groups together elements with similar properties. In most Periodic Tables hydrogen
is placed at the top of Group 1, but in some it is placed at the top of Group 7.
Using your knowledge of chemistry, comment on the reasons for hydrogen being placed above
either Group 1 or Group 7.
9. Oxygen gas speeds up the rate at which food is spoiled. To improve the shelf -life of foods, food
manufacturers use several methods to remove oxygen from inside the food packaging. In one
method, an enzyme is added that catalyses a reaction between oxygen and the glucose which is
often present in foods.
glucose + oxygen + water → gluconic acid + hydrogen peroxide
Using your knowledge of chemistry, comment on why this method may not be suitable to improve
the shelf-life of all foods.
10. Concentrated solutions of hydrogen peroxide are used in the propulsion systems of torpedoes.
Hydrogen peroxide decomposes naturally to form water and oxygen:
2H 2 O 2 (aq) → 2H 2 O(ℓ) + O 2 (g) ΔH = −196∙4 kJ mol –1
Transition metal oxides act as catalysts in the decomposition of the hydrogen peroxide.
Unfortunately, there are hazards associated with the use of hydrogen peroxide as a fuel in
torpedoes. It is possible that a leak of hydrogen peroxide solution from a rusty torpedo may trigger
an explosion.
Using your knowledge of chemistry, comment on why this could happen.
11. The texture and flavour of chocolate comes from a blend of compounds . Using your knowledge of
chemistry, describe how you could show that there are ionic and covalent compounds present in
Q12 Argon was discovered in the 1890’s when samples of nitrogen prepared by different
methods were compared.
The element name was derived from the Greek argos, meaning ‘lazy one’.
2 samples of nitrogen can be prepared as shown.
Method 1: Removing carbon dioxide and oxygen from the air
Method 2: Reaction of sodium nitrite with ammonium chloride
Na NO2(s) + NH4Cl (s) → NaCl (s) + N2 (g) + 2H20 (l)
Heated magnesium metal can react with nitrogen gas to give magnesium nitride
3Mg(s) + N2 (g) + →Mg 3 N2 (s)
Using your knowledge of chemistry comment on the discovery and naming of argon
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