What happens to weathered pieces of rock? | 11-14 years

In this practical activity, students use water in sloping guttering to simulate the process of weathered rock fragments being transported and deposited by a river. From formulating their research questions to building an appropriate model and recording their observations, students get the opportunity to plan, carry out and evaluate their own investigations.

Learning objectives

Students will understand through investigation:

• The factors that affect how fragments of rocks are transported and deposited by water currents.

Sequence of activities

Introduction

Show a short video clip or a still image of a river while sharing the learning objectives with the students.

Choosing a question for investigation

Arrange the students to:

• Work in pairs.
• Draw a picture on a mini whiteboard to show how big, medium and small fragments of rock might be distributed on the bed of a river after a surge of water has passed along it.

With the whole class, ask:

• Some pairs to explain their drawings.
• Questions based on students’ drawings to make explicit the ideas that fragments of similar size are deposited together and that smaller fragments are carried further than larger fragments.

Give a copy of the ‘Activity sheet’ to each student. Explain that they can:

• Use different widths of gutter.
• Alter the height of the sloping gutter.
• Use gravel, sand and muddy water separately or together.
• Pour water from their beaker.

Ask the students to:

• Work in pairs for the whole exercise.
• Write, on their ’Activity sheet’, a question that they can investigate.
• Predict what they think the outcome of their investigation will be.

Manage the range of questions proposed, first by asking some pairs to share the question they wish to investigate and what they predict will be the outcome of their investigation. Then if the questions are very similar, widen the range. Possible questions for investigation include:

• Does the distance that sand travels depend on the width of the guttering?
• Does the distance gravel travels depend on the volume of water that flows over it?
• Does the distance muddy water travels depend on its speed?
• Does sand travel further than gravel when the same volume of water flows over it?
• Does most sand travel the same distance when water flows over it?

Investigation

Circulate and support with prompts while students:

• Plan what they are going to do and write it down on their ‘Activity sheet’.
• Carry out their investigation by using their plan, but modifying it if necessary.
• Record their observations on the ‘Activity sheet’.
• Write down whether the evidence that they have collected supports their prediction.
• Explain their observations, linking together the movement of fragments of rock to the volume and/or speed of water.
• Describe, on their ‘Activity sheet’, what worked well in their original plan, what problems they encountered and how they overcame them.

Plenary

In a plenary, ask different pairs:

• What they recorded and if it supported their predictions.
• What their investigation shows about how water can transport and deposit sediments.
• What worked well in their plan, what problems they encountered and how they overcame them.

Feedback

Take in students’ activity sheets and write feedback on how they can further improve their plan and/or their explanations.

Practical notes

Equipment

• Lengths of wide guttering
• Lengths of narrow guttering
• Gravel
• Sand
• Muddy soil
• Beaker
• Supply of tap water
• Ruler
• Props to support the guttering at different angles
• Large container to catch material flowing from the gutter

Health, safety and technical notes

• Read our standard health and safety guidance.
• It is the responsibility of the teacher to carry out an appropriate risk assessment.
• Possible investigations include:
  • Comparing wide and narrow guttering using the same slope, material and amount of water.
  • Comparing different slopes (achieved by different starting heights) using the same width, material and amount of water.
  • Comparing different amounts of water using the same width, slope and material.
  • Comparing different materials using the same width, slope and amount of water.
  • Comparing the same material using repeated trials with the same width of guttering, slope and amount of water.
• A large container should be provided for each pair of students to catch material flowing out of the guttering and so prevent it going into sinks. A large bucket can also be provided to collect all the debris from beakers at the end of the lesson. (It may be preferable to carry out the practical activity outside.)

Principal hazard

• Water spills

Commentary

Sharing the learning objective is an opportunity to demonstrate how to set an objective for an investigation.

By using mini whiteboards the students give a snapshot of their understanding and so indicate the level of support that they may need. To answer the questions on the worksheet, students will reflect on how well their observations matched their predictions and self-assess the effectiveness of their experiment plan.

Written feedback should make the student aware of how to develop their investigational skills further.

Answers

1. Does the distance that sand travels depend on the width of the guttering?
   • Yes. The wider the guttering the shorter the distance travelled by the sand when the same volume of water flows.
2. Does the distance gravel travels depend on the volume of water that flows over it?
   • Yes. The wider the guttering the shorter the distance travelled by the gravel when the same amount of water flows.
3. Does the distance muddy water travels depend on its speed?
   • Yes. The faster the water the greater the distance travelled by the mud.
4. Does sand travel further than gravel when the same volume of water flows over it?
   • Yes. The sand travels further than the gravel when the same volume of water flows over them.
5. Does most sand travel the same distance when water flows over it?
   • Yes. Most sand travels the same distance when water flows over it.