This document outlines an experiment for students to learn about the scientific method and biodegradation of different materials in water. The main objective is for students to develop hypotheses and imagine possible results. Students will observe and describe properties of paper, bread, an aluminum can, stone, and plastic. They will then develop hypotheses about how each material will be affected by water, and record observations over four weeks to discover the results. Finally, students will draw conclusions about which materials would be most and least dangerous if in oceans.

1. Block 4, Module 4: SCIENTIFIC METHOD.
Experiment based in a PBL based on recycling, through the experiment we are trying to work on
the concept of biodegradation of different materials into the water:
Main objective: Be able to develop hypothesis and imagine possible results of a real
experiment developed in class with different elements.
Which try to work in some way the following learning standards of the official curriculum of
natural sciences in 4th grade.
Est.CN.1.2.1 Realiza cooperativamente tareas, proyectos sencillos y pequeñas investigaciones
sobre el ser humano, la salud, los seres vivos, materia, energía, máquinas, tecnología,
sucesos… iniciándose en el planteamiento de problemas, enunciando alguna hipótesis y
extrayendo conclusiones para realizar un informe final simple.
Pupils observe and take notes of each one of the
following materials that we show them in class:
 Piece of paper
 Piece of bread
 Aluminium can
 Stone
 Piece of plastic (PVC)
Writing a list of their properties using adjectives: soft,
hard, malleable, mouldable, and not mouldable.
Once our pupils are familiarize with the 5 materials we
send them the following questions:
 I wonder if the material will change if we put it
in water.
 Which material do you think will be
biodegraded quicker?
 Which material do you think will be
biodegraded slower?

2. Next, pupils have to develop their own hypothesis
about what is going to happen with each one of the
objects. Examples:
 I think the aluminium can will rust in the water
 I think that the piece of paper will be dissolved.
 In my opinion the stone could be erode by the
water.
 From my point of view the plastic could lose its
colour.
In order to help our pupils we will give them starters to
help them to develop sentences.
Each Monday pupils should take notes of changes and
how each material evolves in a scientific diary:
 I see the paper dissolving in the water.
 I see the plastic in the same way than the first
day.
 I see the piece of bread dissolving in the
water.
After taking notes during 4 Mondays, pupils have to
record their observations and the final result.
 I discovered that plastic will not biodegrade in
water during one month.
 I discovered that paper will biodegrade quicker
than stones.
 I discovered that aluminium can rust in water
and give off metal pieces.
Like in the hypothesis step we can give our pupils
some starters to help them to develop their own
discoveries.

3. Finally, connecting our experiment with the unit, our
pupils should do conclusions imagining this objects in
water jars like if they will be in the oceans.
 In my opinion plastics are the most dangerous
in our oceans because could be eaten by fish.
 From my point of view papers are not as
dangerous as aluminium cans.
 As a conclusion the most dangerous are the
aluminium and plastic and the least dangerous
are paper and bread.
We try to make our pupils their own conclusion basing
this experiments in class with problems in the real
world.