Do now! Can you copy the results from other groups into your table and find the averages?

Science – Evidence!

Measuring

Precision and Accuracy The same thing?

Let’s do some measuring!

You and partnerAverage 1. Length of desk (m) 2. Temperature of room (°C) 3. Period of pendulum (s) 4. Current in circuit (A) 5. Mass of block (g) 6. Area of paper (cm 2 ) 7. Mr Porter’s height (m) 8. Air pressure 9. Light intensity in lab (Lux) 10. Diameter of a hair (mm)

Precision and Accuracy The same thing?

Precision A man’s height was measured several times using a laser device. All the measurements were very similar and the height was found to be ± 0.01 cm This is a precise result (high number of significant figures, small range of measurements)

Accuracy Height of man = ± 0.01cm This is a precise result, but not accurate (near the “real value”) because the man still had his shoes on.

Accuracy The man then took his shoes off and his height was measured using a ruler to the nearest centimetre. Height = 182 ± 1 cm This is accurate (near the real value) but not precise (only 3 significant figures)

Precise and accurate The man’s height was then measured without his socks on using the laser device. Height = ± 0.01 cm This is precise (high number of significant figures) AND accurate (near the real value)

Precision and Accuracy Precise – High number of significent figures. Repeated measurements are similar Accurate – Near to the “real” value Can you copy this please?

You and partnerAverage 1. Length of desk (m) 2. Temperature of room (°C) 3. Period of pendulum (s) 4. Current in circuit (A) 5. Mass of block (g) 6. Area of paper (cm 2 ) 7. Mr Porter’s height (m) 8. Air pressure 9. Light intensity in lab (Lux) 10. Diameter of a hair (mm) Can you decide whether each average is accurate and/or precise and write your answer on the table of results

What is a metre?

The SI system of units There are seven fundamental base units which are clearly defined and on which all other derived units are based:

The metre This is the unit of distance. It is the distance traveled by light in a vacuum in a time of 1/ seconds.

The second This is the unit of time. A second is the duration of full oscillations of the electromagnetic radiation emitted in a transition between two hyperfine energy levels in the ground state of a caesium-133 atom.

The ampere This is the unit of electrical current. It is defined as that current which, when flowing in two parallel conductors 1 m apart, produces a force of 2 x N on a length of 1 m of the conductors.

The kelvin This is the unit of temperature. It is 1/ of the thermodynamic temperature of the triple point of water.

The mole One mole of a substance contains as many molecules as there are atoms in 12 g of carbon-12. This special number of molecules is called Avogadro’s number and equals 6.02 x

The candela (not used in IB) This is the unit of luminous intensity. It is the intensity of a source of frequency 5.40 x Hz emitting 1/683 W per steradian.

The kilogram This is the unit of mass. It is the mass of a certain quantity of a platinum-iridium alloy kept at the Bureau International des Poids et Mesures in France. THE kilogram!

Estimation For IB you have to be able to make order of magnitude estimates (the nearest power of ten).

Estimation/Guess What’s the difference?

Estimate the following: 1.The mass of an apple (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple 2.The number of times a human heart beats in a lifetime. (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple 2.The number of times a human heart beats in a lifetime. 3.The speed a cockroach can run. (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple 2.The number of times a human heart beats in a lifetime. 3.The speed a cockroach can run. (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple 2.The number of times a human heart beats in a lifetime. 3.The speed a cockroach can run. 4.The number of classrooms full of tea Mr Porter will drink in his lifetime. (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple kg 2.The number of times a human heart beats in a lifetime. 3.The speed a cockroach can run. 4.The number of classrooms full of tea Mr Porter will drink in his lifetime. (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple kg 2.The number of times a human heart beats in a lifetime. 70x60x24x365x70= The speed a cockroach can run. 4.The number of classrooms full of tea Mr Porter will drink in his lifetime. (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple kg 2.The number of times a human heart beats in a lifetime. 70x60x24x365x70= The speed a cockroach can run m/s 4.The number of classrooms full of tea Mr Porter will drink in his lifetime. (to the nearest order of magnitude)

Estimate the following: 1.The mass of an apple kg 2.The number of times a human heart beats in a lifetime. 70x60x24x365x70= The speed a cockroach can run m/s 4.The number of classrooms full of tea Mr Porter will drink in his lifetime. (to the nearest order of magnitude)

Your own estimates Read the sheet carefully and then make your own estimates.

If you finish early… Can you write a science question for “The Question Wall”?