Oxford New Century Physics for Queensland

From Dr Richard Walding, BAppSc, MSc, MPhil, PhD, FAIP, FRACI, CChem
Physics teacher - Moreton Bay College, Brisbane
Adjunct Research Fellow - Griffith University, Brisbane



It is essential to be able to understand and respond to cognitive verbs. A nice way to do this is to present intriguing information from the 'Makes you wonder' from chapter openers to capture students' attention:
For example:
Ask: Identify a three-letter English verb that becomes its past tense simply by moving the first letter to the end. Answer: EAT
Demonstration: to get students to distinguish between the cognitive verbs describe and explain, drop an Alka Seltzer tablet (or a Berocca or Hydralyte) into some water and ask students to describe what is happening, and explain what is happening. Describe: a tablet fizzes up when placed in water; explain: the tablet dissolves and the acid reacts with the bicarbonate to produce carbon dioxide (or similar).
Suggested activity 1:
○ Demonstration: to get students to distinguish between the cognitive verbs describe, explainand justify, prepare an inflated balloon out of sight (behind the desk) and prick it with a pin.
Students can: 
'describe' what happens: a loud popping noise;
'explain' what happens: a balloon bursting releases its compressed gas very fast and creates a sound wave, radiating out in the room
'justify' what happens: there is probably evidence of a burst balloon if you look.
•    Suggested activity 2:
○ Demonstration: to get students to distinguish between the cognitive verbs describe, explain, and justify, try the following.  In a very quiet room, drop a dressmaker's pin on to a hard surface.
Students can: 
'describe' what happens: a pin falls from a height and a slight noise is heard when it makes contact
'explain' what happens: the kinetic energy of the pin is reduced to zero, so the energy goes into producing a pressure wave that radiates out as sound to the ears
'justify' what happens: the evidence shows that the pin was at a great height but then fell to a lower height when it struck the bench, and a sound was heard almost straight away.

•    Suggested activity 3:
○ Demonstration: on the board, write symbols such as W, p, ±, ∞ and ask:
'identify' the symbol for pi; 'explain' the meaning of pi.

Extension (for more able)
•    For students who would benefit from an additional challenge, consider the following options:
○ Demonstration: take a long human hair (or cotton thread) and ask students to predict its breaking strain. Take comments and ask what does predict mean (to give the expected result of an upcoming action or event). Ask students to classify the breaking strain by physical quantity and its unit (Answer: force, Newton). Ask students to devise a method to test the breaking strain. Answer: tie loops in either end and hang over a clamp; then add brass masses to the other end until it snaps.
○ Demonstration: This book is printed on paper classified as 80 gsm (80 grams per square metre). The cover is made of 249 GSM paper. Say, 'I want to know the theoretical mass of this book and compare it to the actual mass'. Ask how you would phrase a question with a cognitive verb to achieve this. Answers could include the verbs: determine, propose, design, or compare.

Check whether or not students have grasped the key idea about cognitive verbs and are ready to move on to study mathematical relationships. Do this by asking a multiple choice hinge question – for example:
• Which one of the following verbs means: 'make an idea or situation plain or clear by describing it in more detail or revealing relevant facts'?:
1. Describe
2. Explain
3. Compare;
4. Differentiate

Have students hold fingers up to show the answer.
Answer: 2. Explain.
•Which of the following verbs mean: 'give reasons or evidence to support an answer':
1. Prove
2. Propose
3. Identify
4. Justify
Answer: 4. Justify.