Practical 1- Measurement Of The Density Of Solids

Question 1

What apparatus do we need?

Answer 1

-Solid of choice
-30cm rules
-Vernier callipers
-Balance

Question 2

Resolution

Answer 2

The ‘fineness’ which an instrument can be read to

Question 3

30cm ruler resolution

Answer 3

+- 0.1cm

Question 4

Vernier calipers resolution

Answer 4

=-0.01mm

Question 5

Balance resultion

Answer 5

0.1g

Question 6

Density equation

Answer 6

P = m
—
V

Question 7

How do we know what the absolute uncertainty is?

Answer 7

The smallest measurement the measurer does

Question 8

What do we call the uncertainties involved in this experiment?

Answer 8

Absolute uncertainties

Question 9

How do we calculate % uncertainty?

Answer 9

Absolute uncertainty
—————————- X100
Measurement

Question 10

Parallax uncertainty

Answer 10

Looks like a different number when lined up in different places

Question 11

What’s the phrase for a number looking different when lined up in different places?

Answer 11

Parallax uncertainty

Question 12

What % uncertainty do we want to be below and why?

Answer 12

5%, for reliability

Question 13

How could you describe a % uncertainty that’s incredibly small?

Answer 13

Almost negligible - insignificant and not even worth considering

Question 14

Negligible

Answer 14

Not even worth considering; insignificant

Question 15

What do we do to calculate the % uncertainty in density?

Answer 15

Add up the % uncertainties (always add!)

Question 16

What might we have to do to some of the % uncertainties when adding them together?

Answer 16

For example, the radius is squared in the volume formula, therefore we have to multiply it by 2

Question 17

Method of calculating % uncertainty in density

Answer 17

1. Add up the % uncertainties (length, mass and radius, remembering to multiply the radius by 2 as it was squared in the volume formula!)
2. Answer divided by 100, multiplied by the density itself, giving us the answer to one significant figure

Question 18

Do we involve the % uncertainties when working out the density?

Answer 18

No, just the figures as usual

Question 19

To how many significant figures do we want the % uncertainty for the density?

Answer 19

1

Question 20

How can the radius of a sphere be accurately calculated?

Answer 20

Using vernier calipers

Question 21

How do we calculate the absolute uncertainty from the percentage uncertainty?

Answer 21

Percentage uncertainty of answer