1. Chapter 2 Measuring Length - Introduction to instruments and units used

2. Introduction 1. Observation is a science process skill used in investigations 2. Observations • Qualitative • Quantitative 3. Qualitative observations -5senses -descriptions e.g. It is smooth. The gas is pungent and colourless. It is moving quickly. 4.Quantitative observation -accurate measurements using instruments e.g metre rule, measuring tape, vernier calipers, measuring cylinder, pipette, burette, electronic balance, spring balance

3. Physical Quantities 1. A physical quantity is a quantity which can be measured. e.g. length, area, volume, time, temperature, mass 2. A non-physical quantity is one which cannot be measured. e.g beauty, kindness, humour, sadness, untidiness

4. Exploring Science 1-CDIS

5. Physical Quantity SI Unit Symbol SI Unit length metrem time second s kilogram kg mass newton N weight

6. Measuring Length SI unit: metre (m) millimetre (mm) andcentimetre (cm) Smaller units: 1 m = 100 cm 1 m = 1000 mm 1100 11000 1 cm = m 1 mm = m =0.01 m 1 cm = _____ mm 10

7. Instruments for Length -metre rule and measuring tape -accuracy of 0.1 cm (1 mm)

8. Instruments for Length External Caliper - accuracy of 0.1 cm Internal Caliper - accuracy of 0.1 cm

9. External Calipers Measuring the external diameter of a beaker

10. External Calipers Measuring the external diameter of a beaker

11. Internal Calipers Measuring the internal diameter of a beaker

12. Internal Calipers Measuring the internal diameter of a beaker

13. Vernier Calipers -for measuring short lengths -accuracy of 0.01 cm or 0.1mm

14. Physics - A Course for ‘O’ Level Federal

15. Physics - A Course for ‘O’ Level Federal

16. Parallax Error is an error in a measurement due to the eye not being in the correct position when taking a reading. For accurate measurements using the metre rule or measuring tape, the eye must be placed vertically above the mark being read to prevent parallax error.

17. Micrometer Screw Gauge - accuracy of 0.001 cm

18. Micrometer Screw Gauge anvil sleeve thimble ratchet spindle frame

19. When using a ruler, parallax errors can be avoided by - placing the eye vertically above the marking on the scale to be read. - placing a thick ruler on its edge beside the object to be measured so that the scale is touching it - using a thin ruler so that the scale is touching the object to be measured