Review the previous lesson, where the class conducted an investigation into whether the shape of an object affected its ability to roll. If, during that investigation, students made any observations or comparisons about the materials that the objects were made out of, draw attention to these. If not, display the items that were tested in the previous lesson and discuss the materials they’re made of and how they are different.

Ask students to describe again the movement of rolling, and how it is different to sliding. Make an obvious mark on an object and watch that mark as the item slides across a surface. Define sliding with or for students as appropriate (moving smoothly along a surface whilst staying in contact with that surface).

Examine the different objects that students will slide across the table or other smooth surface, with a focus on the different materials they are made of/covered in. Allow students to feel and examine each material and describe how they look and feel. Construct (with guidance if needed) comparative statements about them such as, "The _____ is smoother that the _______".

Ask students if they think one objects will slide further than the other, and why they think that.

Pose the question: Will changing the material (of/on) an object affect how far it can slide across the surface of a table?

Using the demonstration copy of the Sliding investigation Resource sheet complete the Predict and Reason sections of the PROE (Predict, Reason, Observe, Explain), based on the earlier discussion and any new ideas students would like to add. You can support students with this by making connections between their previous experiences of using a slide, or sliding across a slippery floor.

Discuss how the class will test whether different materials affect how far an object will slide across a table/surface.

With students, determine:

1. What will be changed in the investigation (the material on the sliding surface).
2. What will be measured in the investigation (the distance the object slides).
3. What will stay the same in the investigation (the standing starting point when sliding the object, who slides the object, the surface/table etc.).

Each of the variables that need to be kept the same can be discussed as is appropriate for your students. In particular, it is likely that all students will want an opportunity to slide the objects across the surface of the table. This can be done if time and resources allow, however, measuring and recording the distance of each student’s attempts will take a significant amount of time. Consider if this is right to do in your context. Alternatively, you might allow all students the opportunity to slide the objects, but only record the measurements of one or a few students.

Next, determine a suitable way of measuring the distance of each slide. If your students are ready for complexity, the following steps describe a new measuring technique which will demonstrate the importance of using standard units of measurement. Alternatively, you may choose to use the streamer method from the previous lesson.

1. Explain that you will begin with a ‘test’ slide. Mark a start line on a table or other smooth flat surface.
2. Conduct the test slide and mark the final location of the object on the table/surface.
3. Optional: Suggest counting how many ‘hands’ between the start line and final location and ask students if they think there might be any problems with this method.
4. Select as many students as needed to place both hands on the table/surface to fill the distance between the start line and the object’s final location. Don’t give any direction as to how they might place their hands. Record this measurement.
5. Next, select different students to measure the same distance by placing their hands in a row with each fingertip touching the bottom of the palm/wrist of the next hand. Record this measurement.
6. Model critical thinking by wondering aloud if the measurements were fair and how to make them so. Discuss with students if the size of the hands would make a difference (small hands will allow for short measurements) or if the way the hands are placed (spread fingers measuring thumb to pinky can vary in how far they are spread each time) would change the measurement. Look at how the different way of placing the hands also affects the measurement.
7. Next, introduce standard ‘handprint measurements’ created using the Hand measures Resource sheet.
8. Determine which direction you'll agree to use (bottom of palm to fingertip, or thumb to pinky).
9. Measure the distance of the test slide with the handprint measurements and record it.
10. Shuffle the handprint measurements around, measure the distance again, and record the measurement. It should be the same distance.
11. Discuss and determine with students why using the handprint measurements is more accurate than using their own hands: the measurements are all the same size, so it’s more fair to compare them.

Use the appropriate measurement tool to complete the investigation as either a whole class, in collaborative teams with an adult or older student helper, or in collaborative teams that work independently if students are ready. 

If investigating as a whole class, you may choose to:

• have only one student undertake the slides that are measured.
• measure the tests from multiple students.
• allow all students to slide and measure. 

Make a simple column graph for students by placing the streamers next to each other, or make a bar graph by placing the correct number of handprints from the end of the palm to the fingertip on a labelled axis.

Discuss and compare the results shown on the graph with students’ predictions made earlier in the lesson about which object might slide the furthest.

Present students with the statement: objects made of different materials move in different ways. Ask students if they agree with this statement or not, and why. Ask students to draw on examples they have seen over the course of the sequence to support their ideas.

You might prompt their thinking with the following examples:

• think back to some of the objects passed around the circle in Lesson 1. Were they easy or hard to move in different ways, and why?
• consider the different movements made with the equipment used when students played the playground games.
• consider how far different objects rolled in the previous lesson, and if the material they were made of affected how far they rolled.
• consider how some materials were able to slide more easily than others.

Reflect on the lesson 

You might:

• ask students to think about which other factors may influence how far something is able to slide.
• add to the class word wall any vocabulary related to materials, fair testing, investigations, etc.
• re-examine the intended learning goals for the lesson and consider how they were achieved.
• discuss how students were thinking and working like scientists during the lesson. Focus on the importance of having a fair and accurate way of taking measurements.