Homework: Atoms, Elements and Compounds – Levels 6–8
Atmosphere on Mars
In 2004, two space probes landed at different places on Mars. They sent back
information about the atmosphere on Mars.
The tables show some information about the atmosphere on Mars and on Earth.
Atmosphere on Mars
Atmosphere on Earth
Name of gas
Formula
Percentage
Name of gas
Formula
Percentage
carbon
dioxide
CO2
95%
nitrogen
N2
78%
nitrogen
N2
3%
oxygen
O2
21%
other gases
various
2%
other gases
various
1%
The diagram shows how the particles of gas are arranged in the atmosphere on
Earth:
nitrogen
oxygen
Task
Use what you have learnt about atoms, molecules, elements, compounds and
mixtures to:

identify some differences between the atmosphere on Earth and on Mars

explain, using examples from the tables, the differences between an element,
a compound and a mixture and the difference between an atom and a molecule

make a table to show the names and numbers of atoms in the molecules of the
gases in the table

give reasons why the diagram of the particles in air is a good model but is not a
true representation of particles in real air.
Mark Scheme
Level
You should:
6

explain the meaning of ‘compound’ in terms of atoms


explain how compounds are different to mixtures
identify at least three differences between the atmosphere on
Earth and on Mars by talking about both the types of gases and
the percentages.
7


explain the difference between an atom and a molecule
draw a table to show the names of each element in the gases
on Mars and on Earth with the number of atoms in each
molecule of gas.
8

describe at least one reason why the diagram of particles in air
is a good model, for example ratio of nitrogen to oxygen,
particles are arranged as in a gas, mixture of particles shown
identify at least two reasons why the model of air is different
to real air using ideas about size or closeness of particles,
missing gases or molecules shown as single atoms.
