Rusting nails
| Y6 (08/2006) | ||
| a) |
No Yes Yes Yes |
all correct – moderate |
| b) |
Same type of nail (made of the same metal) - given
Different types of water (1 salt, 1 fresh) Same amount of water Same length of time
For example
 |
all correct – moderate |
This task provides a quick check on managing variables when planning a fair test. For this to be a meaningful task it is expected that students will follow up by carrying out the investigation after their planning has been checked. Students can work in groups or independently, or, particularly if the skill is being introduced, the whole class can work together.
Rusting
While the assessment focus is on the process of planning a fair test, the purpose of planning this investigation is to add to knowledge about rusting. Rust is a type of corrosion. Rusting is the formation of iron oxide from corroding iron. There are three elements necessary for rusting:
- Iron
- Water
- Oxygen
Salt in seawater or the air, and also acid rain, increase the rate of rusting. Copper will not rust (because there is no iron). Steel will rust because it is an alloy containing iron. Teachers can help their students make sense of their investigations by asking probing questions about what they are finding out from their investigations.
An analysis of children's investigations based on three NEMP tasks (Hipkins and Kenneally, 2003) suggested that, until they have had a lot of experience, students need some structure to organise their intuitive ideas about fair testing. This resource models one way of providing support for students to "hold" information in their heads. Some of the trial students obviously did not use the nail cue in Question b) when completing Question a), that is, they did not go back and modify their response.
Next steps
Strategies to support students to plan investigations If the responses appear to be random and there is no consistency between the two questions:
- provide specific teaching about what a fair test is.
If there is a consistent mistake in both parts:
- focus on the investigative question.
If 1 question is right and the other wrong or 1 variable is inconsistent:
- ask students to compare the two parts.
If students have all variables the same:
- go back to the investigative question. What will you find out if both are the same?
Other strategies that help students organise variables are modelled in other ARB resources (see Further resources).
Follow up activities
After the students have set up their investigations use their marked answers to check their work (self-assessment).
Change the question and replan which variable needs to be changed (independently, in groups, or all together).
- Will a steel nail or a copper nail rust more quickly?
- Will a nail rust more when it is partly covered or fully covered by water?
Carry out the investigations.
Ask students to consider the question: When might it be important to know what makes nails rust? Did they gather enough information to answer the question?
Rolling marbles models another strategy for supporting students to manage variables, but in the context of rolling marbles.
Rolling marbles II is a similar resource at Level 2, and provides even more support.
Ministry of Education (2003). Building Science Concepts, Book 32, Introducing Metals. Wellington: Learning Media.
Ministry of Education (2003). Building Science Concepts, Book 33, Working with Metals. Wellington: Learning Media.
Further reading about children's investigative skills:
Ministry of Education (2003). NEMP probe study findings 2003. Dunedin: Educational Assessment Research Unit. Developing children's science investigation skills, page 14, provides a clear teacher-friendly summary of a research project by Rose Hipkins and Natasha Kenneally about children's science investigation skills.
Hipkins, R. and Kenneally, N. (2003). Using NEMP to inform the teaching of science skills. Wellington: New Zealand Council for Educational Research.
Hipkins, R. and Kenneally, N. (2003). Simple teaching strategies to use during primary science investigations. Paper presented at ASERA Conference, Melbourne, July 8-12, 2003.