What Does It Mean If The Change In Mass Is A Positive Number
Transport in cells
Diffusion is the move of particles from a high to lower concentration. Osmosis is the improvidence of h2o beyond a membrane. Active transport moves particles from low to higher concentration. Exam / not-test assessments for students taking qualifications during the pandemic may be subject to alter. Delight check with your teacher.
Maths - Calculating per centum gain and loss of mass in osmosis
Analysing results
The investigation cannot exist based on changes in mass from just i tater cylinder. In scientific tests, we must ensure a number of examples are used to allow for anomalous results and variation.
Percentage changes in mass must be calculated for each cylinder and hateful calculated.
A graph is plotted of alter in mass, in per cent, confronting concentration of sucrose . Concentrations of solutions are shown as percentages. A larger number means a higher concentration.
Where potato cylinders have gained in mass, the modify will be positive. Where white potato cylinders have decreased in mass, the change will be negative.
| Concentration of sucrose % | Boilerplate change in mass (%) |
|---|---|
| 0 | +26.8 |
| xx | +5.0 |
| xl | −7.7 |
| 60 | −17.9 |
| 80 | −26.0 |
| 100 | −31.iv |
Where the plotted line crosses the horizontal axis at 0 per cent alter in mass, the sucrose concentration of the solution is equal to the concentration of the contents of the potato cells.
This tin can be identified on the graph as the point which shows no net movement of water by osmosis , which would be represented by a change in mass.
- Question
-
What is the concentration of solutes in the cells of the tater in this investigation?
-
29%
This value is where the line crosses the 10-axis.
Percentiles
The concentration of dissolved solutes in the cells of dissimilar potatoes will vary slightly from potato to potato. If we take a set of data for a range in concentrations, nosotros tin can look at the range , and the mean - but these exercise not tell us whether data are evenly spread or whether they are amassed together inside a certain range.
Scientists use percentiles to divide a prepare of data into 100, and look to see where the data prevarication within these divisions.
The median is the point in a ready of information where l per cent of the information fall higher up this value, and 50 per cent below it. This is the 50 th percentile.
The 75 thursday percentile is where 75 percent of the data fall beneath this value.
There are several methods of finding a percentile. The simplest is the nearest rank method. As with finding the median of a set of data, brainstorm by putting the data into guild.
For a range of values for the concentration of spud cell sap:
| 0.27 | 0.32 | 0.25 | 0.24 | 0.28 | 0.31 | 0.thirty | 0.26 | 0.29 | 0.29 | 0.31 | 0.35 | 0.21 | 0.28 | 0.28 | 0.26 |
| 0.35 | 0.22 | 0.27 | 0.26 | 0.24 | 0.23 | 0.39 | 0.28 | 0.29 | 0.27 | 0.26 | 0.25 | 0.30 | 0.27 | 0.25 | 0.26 |
Arranged in order:
| 0.21 | 0.22 | 0.23 | 0.24 | 0.24 | 0.25 | 0.25 | 0.25 | 0.26 | 0.26 | 0.26 | 0.26 | 0.26 | 0.27 | 0.27 | 0.27 |
| 0.27 | 0.28 | 0.28 | 0.28 | 0.28 | 0.29 | 0.29 | 0.29 | 0.xxx | 0.thirty | 0.31 | 0.31 | 0.32 | 0.35 | 0.35 | 0.39 |
To find, for case the 50 thursday percentile, commencement find the rank:
\[\text{ordered rank} = \frac{\text{percentile}}{100} \times \text{number of entries in data set}\]
\[\text{ordered rank} = \frac{50}{100} \times 32 = 16\]
And then the l thursday percentile will be the 16 th number in the ordered data ready, starting from the left. The 50 th percentile is 0.27.
| 0.21 | 0.22 | 0.23 | 0.24 | 0.24 | 0.25 | 0.25 | 0.25 | 0.26 | 0.26 | 0.26 | 0.26 | 0.26 | 0.27 | 0.27 | 0.27 |
| 0.27 | 0.28 | 0.28 | 0.28 | 0.28 | 0.29 | 0.29 | 0.29 | 0.thirty | 0.30 | 0.31 | 0.31 | 0.32 | 0.35 | 0.35 | 0.39 |
In instances where the ordered rank is not a whole number, yous should round the number upwardly.
- Question
-
Observe the 90 th percentile for the same set of data.
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0.32 mol dm −three .
\[\text{ordered rank} = \frac{\text{percentile}}{100} \times \text{number in data set}\]
\[\text{ordered rank} = \frac{90}{100} \times 32 = 29\]
This method will only give percentiles as numbers that exist in the information set.
In other methods, percentiles tin can be interpolated for values that don't exist in the data prepare.
Source: https://www.bbc.co.uk/bitesize/guides/z22vw6f/revision/7
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