Materials: Density

Q4. Barry investigated the density of different fruits.

To determine the density of each fruit, he measured the volume of each fruit.

The diagram above shows the equipment he used.

(a) Describe a method Barry could have used to measure the volume of an orange, using this equipment.

This type of question is marked in two ways:

- the examiner looks for relevant points

- but also for a logical sequence...

It is not just a 'tick fest' - but a marker does look to see how many relevant points you have made, then considers how you have strung them together to put your answer into a 'level'

Level 2:	The method would lead to the production of a valid outcome. The key steps are identified and logically sequenced.	3 - 4 marks
Level 1:	The method would not necessarily lead to a valid outcome. Some steps are identified, but the method is not fully logically sequenced.	1 - 2 marks
Level 0:	No relevant content	0 marks

 

Indicative content:

use the beaker to fill the eureka/displacement can with water

fill the eureka/displacement can up to the spout

put the measuring cylinder in a position so it can collect water coming out of the eureka can spout

place the orange gently in eureka/displacement can

collect water that overflows

measure volume of water collected in the measuring cylinder

repeat the process

[4 marks]

(b) He measured the volume of each fruit three times and then calculated a mean value.

(i) What are the advantages of taking three measurements and calculating a mean value?

Choose your answer fom the following reasons:

[2 marks]

(ii) The three measurements for the volume of a grape were 2.1 cm³, 2.1 cm³ and 2.4 cm³.

Calculate the mean value he should use for the grape.

The 2.4 cm³ is an anomaly. It should therefore be ignored when calculating a mean value. In fact it should have been repeated at the time of the experiment!

Ignoring the anomoly 2.4 cm³

the mean value =

(2.1 + 2.1) /2 = 2.1 cm³

If you did not explain that the 2.4 cm³ is an anomaly you could get 2 marks:

the mean value = (2.1 + 2.1 + 2.4) /3 = 2.2 cm³

[3 marks]

(c) The mass of an apple was found to be 84.0 g. The volume of the apple was calculated as 120 cm³.

Calculate the density of the apple. Give the answer to the corect number of significant figures.

density = mass/volume

ρ = m/V

ρ = 84.0/120 = 0.700 g/cm³

Values were given to 3sf - therefore the answer should be given to 3sf too.... those zeros after the 7 matter!

[5 marks]

[Total: 14 marks]