<u>Answer:</u> The average of the densities of the given measurements is 1.363 g/mL
<u>Explanation:</u>
The equation used to calculate density of a substance is given by:

We are given:
First measured value of density,
= 1.019 g/mL
Second measured value of density,
= 1.498 g/mL
Third measured value of density,
= 1.572 g/mL
Putting values in above equation, we get:


Hence, the average of the densities of the given measurements is 1.363 g/mL
Answer:
±0.005 g
Explanation:
The uncertainty depends on whether the measurement was obtained manually or digitally.
1. Manual
The minimum uncertainty is ±0.01 g.
It may be greater, depending on random or personal errors
2. Digital
Most measurements of mass are now made on digital scales.
A digital device must always round off the measurement it displays.
For example, if the display reads 20.00, the measurement must be between 20.005 and 19.995 (±0.005).
If the measured value were 20.006, the display would round up to 20.01.
If the measured value were 19.994, the display would round down to 19.99.
The uncertainty is ±0.005 g.
The scale shown below would display a mass of 20.00 g
6.02214086 x 10^23 mol^-1
It's because they add to its hardness . Calcium is naturally dissolved in water