Plants, Matter and Energy
Technical & Teaching Notes
Related sheets
Plant reactions; Plant nutrients; Making and testing nutrients; Homemade fertilisers; Soil culture;
Water culture; Floating culture
Introduction and context
To grow healthily a plant needs: air, water, nutrients, light and warmth. These are needed for the
vast numbers of chemical reactions that happen as a plant grows.
Matter: Air, water and nutrients are the starting point for the chemical reactions that happen to
‘build’ a plant. They are all forms of matter.
Energy: Light and warmth are about transferring energy. Light is one way that energy can be
transferred from place to place. Warming and cooling are two of the effects than may happen
when energy is transferred.
The two groups come together whenever change happens, whether it be a physical change or a
chemical reactions and physical changes.
This session is about matter and energy in the context of growing plants and consists of four
activities:
1. Matter and particles – uses the particle model to describe matter and changes of state
2. Particles in air and water – uses ideas about atoms, elements and compounds; atoms and
molecules as two type of particles; forces of attraction between particles; forces of attraction
between atoms bonded in a molecule; salts; ionic lattice
3. Particles in nutrients – uses ideas about atoms, electrons, electrical charge and ions as a
third type of particle
4. Energy – uses ideas about energy stores and energy transfers when changes of state
happen
Possible barriers to learning
The session allows a number of common misconceptions and other hindrances to learning
associated with the particle model of matter and changes of state. These include:

particles are the same, for example, as grains of sugar and flecks of dust

there is air between particles

particles expand on heating

when ice is heated its particles melt

particles in a liquid are smaller than in a solid.
In addition, the misconception that ‘salts’ are the same as salt (sodium chloride) may be
addressed.
Links to National curriculum for science in England at key stage 3
In biology pupils should be taught about nutrition and digestion, which includes:

plants making carbohydrates in their leaves by photosynthesis and gaining mineral nutrients
and water from the soil via their roots
Science & Plants for Schools: www.saps.org.uk
Plants, Matter and Energy: p. 1
In chemistry pupils should be taught about the particulate nature of matter and about atoms,
elements and compounds. This includes:

the properties of the different states of matter (solid, liquid and gas) in terms of the particle
model, including gas pressure

changes of state in terms of the particle model

a simple (Dalton) atomic model

differences between atoms, elements and compounds
In physics pupils should be taught about changes in systems and about the particle model. This
includes:

energy as a quantity that can be quantified and calculated; the total energy has the same
value before and after a change

comparing the starting with the final conditions of a system and describing increases and
decreases in the amounts of energy associated with movements, temperatures, changes in
positions in a field, in elastic distortions and in chemical compositions

the differences in arrangements, in motion and in closeness of particles explaining changes
of state, shape and density, the anomaly of ice-water transition
Equipment and materials
All that students need is pen or pencil (a choice of colours might be helpful) and paper
Teaching Notes
Activity 1: Matter and particles
Matter and various particle models to describe it are key scientific ideas. This activity uses the
three kinds of matter needed by plants – air, water and nutrients – as a context for applying ideas
about particles, states and matter and changes of state.
Two common misconceptions are that

when a substance expands the particles expand

when a substance melts, the particles melt.
It’s crucial that students understand that no matter what its state, the particles of any one
substance are always the same. It’s only the way they are arranged and move that changes.
Answers
1.
Solid
Particles are arranged randomly. They are close together and move
around one another.
Liquid
Particles are arranged in a regular way, close together. They vibrate in
a fixed position, but cannot move from place to place.
Gas
Particles are arranged randomly. They are far apart and move quickly
in all directions.
2. Strongest in solids and weakest in gases.
3. (a) Any suitable diagrams, (b) Freezing (or solidification), (c) Water vapour (a gas)
Science & Plants for Schools: www.saps.org.uk
Plants, Matter and Energy: p. 2
Activity 2: More about particles: atoms and molecules
This activity develops and refines the idea of particles by using Dalton’s model of atoms. ‘Circle
diagrams’ are used to show the types and numbers of atoms that combines to form a compounds
and which atoms are bonded to which. However, they do not show the size or geometry of the
particle.
Particles may be atoms (but only in Group 0 elements (the noble gases), molecules or ions.
Students must be clear about the use of the word ‘particle’ in science. Particles are the building
blocks of elements and compounds. Some students may be confused about the difference
between a ‘scientific particle’ and, for example, a particle of dust
Answers
1.
(a) Nitrogen, oxygen and argon are elements; carbon dioxide is a compound
(b) Carbon dioxide
2.
(a) Suitable diagrams, e.g.
O
H
O
N
H
N
Ar
Ar
O2
N2
O
C
H
O
CO2
(b) Ar atoms, other three molecules
3.
(a)
H
O
H
H
H2O
The two pictures on the right
are ball-and-stick and space-filling models of a water molecule. Students might be shown these
(or models made from kits) and use them to discuss the way scientists represent molecules.
Space-filling shows the overall shape, while ball-and-stick (or exploded model) is used more often
because it makes the shape and position of bonded atoms clearer, especially for large molecules.
(b) The particles (water molecules) gain energy and jiggle around more rapidly. When they gain
sufficient energy they break free from their fixed positions in the solid and become free to move,
but remain close together.
Activity 3: More about particles: atoms and ions
In air the particles are molecules, except for argon where they are atoms. However, the particles
in many solids are ions – atoms which have transferred or gained electrons and, as a result, carry
an electric charge.
Circle diagrams are used to represent them, but no ‘internal structure’ is shown (students are
introduced to these if they do the sheet Plant nutrients).
Students must be clear about the use of the word ‘salt’ in science. Many students may think that
‘salt’ is sodium chloride. However, a salt is the type of compound formed when an acid
neutralises a base. Sodium chloride is just one example.
Science & Plants for Schools: www.saps.org.uk
Plants, Matter and Energy: p. 3
Answers
1. (a) potassium ions, chloride ions; KCl. (b) ammonium ions, nitrate ions; NH4NO3, (c)
ammonium ions, sulfate ions; (NH4)2SO4, (c) calcium ions, phosphate ions; Ca3(PO4)2, (d)
magnesium ions, sulfate ions; MgSO4
2. (a) potassium hydroxide and hydrochloric acid, (b) ammonia and sulfuric acid.
3.
+
K
-
Cl
+
K
-
Cl
-
Cl
+
K
-
Cl
+
K
+
-
-
Cl
+
K
-
Cl
+
K
Cl
K
-
Cl
+
K
+
-
Cl
K
-
Cl
+
K
+
K
-
Cl
+
K
-
Cl
-
Cl
+
K
-
Cl
+
K
+
K
-
Cl
+
K
-
Cl
layer immediately below
first layer
-
+
K
-
Cl Cl
+
K
+
K
-
Cl
Cl Cl
+
K
+
K
Cl Cl
+
K
-
Cl
Cl Cl
+
K
+
K
-
+
K
K
-
+
K
-
+
K
-
+
K
Cl Cl
+
Cl
K
-
+
K
-
+
Cl
Cl Cl
+
K
4. Water molecules are attracted to the charged particles (ions), surround them and carry them
off into solution. The movement of the charged particles has similarities to the movement of
particles in a gas, except that there is water between them rather than empty space.
Activity 4: Energy
This activity asks student to think about energy in the context of plants. Important concepts are
energy stores and energy transfers.
A crucial idea for students to grasp is that energy is not a material. It does not have mass, but we
can measure amounts of energy. It cannot be created or destroyed, but it can be moved from
place to place.
There has been much discussion in recent years about the most suitable model to use with
younger students to describe energy.
Two models can be used.


Energy comes in comes in different forms, like heat, light and chemical energy. When change
happens, energy is transformed from one form to another.
All substances store energy. When a change happens, energy is transferred from one store
to another, mechanically, electrically, by heating or by radiation.
Science & Plants for Schools: www.saps.org.uk
Plants, Matter and Energy: p. 4
We have been encouraged increasingly to use the second – All substances store energy. When a
change happens energy is transferred from one store to another, mechanically, electrically, by
heating or by radiation.
The argument is that we need to help students to understand that energy is just energy. It does
not come in difference forms. So energy is not transformed, rather it is transferred from one
energy store to another. However, it can be transferred in various ways.
Answers
1. It is stored in the Sun and transferred by light wave (electromagnetic radiation).
2. Glucose. It stores energy as a result of the chemical bonds within the molecules and, to a
lesser extent, weaker bonds between molecules (intermolecular bonds) and the vibrations of
glucose molecules about their fixed positions in the solid.
3. During respiration glucose reacts with oxygen to produce carbon dioxide and water. The
reactants store more energy than the products, so when reaction happens energy is released (it
is an exothermic reaction). This energy is transferred to the surroundings, which in this case is
the materials in the plant cell where respiration happened.
Students investigate this further if they use the sheet Plant reactions.
Science & Plants for Schools: www.saps.org.uk
Plants, Matter and Energy: p. 5