Atoms, Elements and Compounds: Exam Drill - Worksheets, Questions and Revision

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KS3 · Chemistry

K7D Atoms, Elements and Compounds: Exam Drill

AQA AQA KS3 Science - Chemistry · Calculator allowed · about 75 minutes
Name: _______________________________    Date: ____ / ____ / ______
Answer ALL questions. Show all your working.
1
Which of the following is a mixture rather than a pure element or compound?
  • A) Neon gas
  • B) Crude oil
  • C) Copper metal
  • D) Carbon dioxide
2
In a neutral atom, which two subatomic particles are always present in equal numbers?
  • A) protons and neutrons
  • B) protons and electrons
  • C) neutrons and electrons
  • D) protons, neutrons and electrons are always equal
3
Define each of the following terms in your own words.
(a)Define the term 'element'.(1)
(b)Define the term 'compound'.(1)
(c)Define the term 'mixture'.(1)
4
The maximum number of electrons that can occupy the first three electron shells (energy levels) of an atom are 2, then 8, then 8. Use this rule and the atomic number (the number of protons, which equals the number of electrons in a neutral atom) to work out the electron configuration of each atom below.
(a)Oxygen has atomic number 8. State its electron configuration (the number of electrons in each shell).(2)
(b)Aluminium has atomic number 13. State its electron configuration.(2)
(c)Calcium has atomic number 20. State its electron configuration.(2)
5
Dry air is a mixture of gases in these approximate percentages by volume: nitrogen (N2) 78%, oxygen (O2) 21%, argon (Ar) 0.9%, carbon dioxide (CO2) 0.04%, with the remainder made up of other gases.
(a)Calculate the percentage of dry air made up of 'other gases'.(2)
(b)Classify nitrogen (N2), argon (Ar) and carbon dioxide (CO2) as an element or a compound.(3)
(c)State why 'air' itself is described as a mixture rather than a compound.(1)
6
Balance each symbol equation below by writing the correct numbers in front of the formulas where needed.
(a)Balance: Ca + O2 -> CaO(2)
(b)Balance: H2 + Cl2 -> HCl(2)
7
Iron filings and powdered sulfur are mixed together and then heated strongly. They react to form the compound iron sulfide.
(a)Write a word equation for this reaction.(2)
(b)The unbalanced symbol equation is Fe + S -> FeS. State whether this equation needs balancing, and explain your reasoning.(2)
8
Use these relative atomic masses (Ar): H = 1, N = 14, Mg = 24, O = 16, Na = 23, C = 12. The relative formula mass (Mr) of a substance is found by adding together the Ar values of all the atoms shown in its formula.
(a)Calculate the relative formula mass (Mr) of ammonia, NH3.(2)
(b)Calculate the relative formula mass (Mr) of magnesium oxide, MgO.(2)
(c)Calculate the relative formula mass (Mr) of sodium carbonate, Na2CO3. Show your working.(3)
9
Rock salt is a naturally occurring mixture of salt (sodium chloride) and insoluble rocky material (mostly sand and grit). A technician wants to obtain pure, dry salt crystals from 40 g of rock salt.
(a)Below are four steps from the method, listed in the wrong order. 1: Filter the mixture to remove the insoluble rock. 2: Crush the rock salt into small pieces using a pestle and mortar. 3: Gently evaporate the filtrate until dry salt crystals remain. 4: Add water and stir well to dissolve the salt. Write the four steps in the correct order.(4)
(b)Explain why the rock salt is crushed before adding water.(1)
(c)The technician recovers 34.2 g of dry salt crystals from the 40 g of rock salt. Calculate the percentage of the original 40 g mass that was recovered as salt crystals.(2)
10
Classify each of these elements as a metal or a non-metal: potassium, phosphorus, silver, neon, iron, bromine.
(3)
11
Carbon has several isotopes, including carbon-12 and carbon-14. Both have atomic number 6.
(a)Explain what is meant by the term isotope, using carbon-12 and carbon-14 as examples.(3)
(b)Calculate the number of neutrons in an atom of carbon-14.(1)
12
Required practical: a long glass tube, 60 cm in length, is set up horizontally. A piece of cotton wool soaked in concentrated ammonia solution is placed at one end (end A) and a piece of cotton wool soaked in concentrated hydrochloric acid is placed at the other end (end B) at the same moment. The two gases diffuse along the tube and react where they meet, forming a white ring of solid ammonium chloride. After 60 seconds, the ring has formed 36 cm from end A.
(a)Calculate the mean rate at which the ring formed, in cm per second, measuring the distance from end A.(2)
(b)Explain, in terms of particles, why a white ring forms where the two gases meet, rather than the gases simply staying at each end of the tube.(2)
(c)The ring forms closer to the hydrochloric acid end (end B) than to the ammonia end (end A). Suggest one reason for this, based on the particles involved.(2)
13
From Question 8, the relative formula mass (Mr) of magnesium oxide (MgO) is 40, and magnesium has relative atomic mass (Ar) 24.
(a)Calculate the percentage by mass of magnesium in magnesium oxide.(2)
(b)Calculate the percentage by mass of oxygen in magnesium oxide.(1)
(c)A sample of magnesium oxide has a mass of 15 g. Assuming the same percentage composition, calculate the mass of magnesium it must have contained.(2)
14
For each statement, identify whether it is True or False. If a statement is false, give the correct version.
(a)An atom of any element always has the same number of protons as electrons, if the atom is neutral.(1)
(b)The relative formula mass of a compound is always found by simply adding up the atomic numbers of the atoms in its formula.(1)
(c)A molecule of a compound must contain atoms of at least two different elements.(1)
(d)Mixtures always have a fixed, unchanging ratio of their components, in the same way that compounds do.(1)
15
State the number of atoms of each element present in the following formulas.
(a)State the number of atoms of each element in one molecule of glucose, C6H12O6.(3)
(b)State the number of atoms of each element in one formula unit of ammonium sulfate, (NH4)2SO4.(2)
16
State the general term used to describe the strong forces that hold atoms together within a compound.
(1)
17
When 12 g of carbon is completely burned in oxygen, 44 g of carbon dioxide gas is produced. Calculate the mass of oxygen that must have reacted with the carbon, using the idea of conservation of mass.
(3)
18
Iron filings and powdered sulfur can be mixed together to make a grey powder, or heated together to react and form the compound iron sulfide. Explain how you could tell, using simple tests, whether a grey powder sample is the original iron-and-sulfur mixture or the compound iron sulfide, and explain why the two samples behave differently. Refer to separation methods and particle theory in your answer.
(6)
Mark scheme · K7D Atoms, Elements and Compounds: Exam Drill

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18