Certainly! Here is a step-by-step explanation for how to draw the necessary markings on glassware to measure the specified volumes of water.
### 128.7 mL
For measuring 128.7 mL, you will typically use a graduated cylinder which is designed to measure liquid volumes with reasonable accuracy.
1. Choose the appropriate graduated cylinder: Since 128.7 mL is a relatively large volume, a graduated cylinder with a total capacity of at least 150 mL would be suitable.
2. Marking Intervals:
- Graduated cylinders commonly have markings at every 1 mL for volumes above 10 mL.
- The markings should be labeled at every 10 mL for easy reading.
3. Identifying the specific volume:
- Locate the marking for 120 mL.
- Locate the marking for 130 mL.
- Between these two markings, the cylinder should have 1 mL interval markings.
- Count up by ones from 120 mL, passing 125 mL and 128 mL.
- Between 128 mL and 129 mL, estimate the 0.7 mL marking by visually dividing the distance into ten equal parts and going 7 parts beyond the 128 mL mark.
### 18 mL
For measuring 18 mL of water, a smaller graduated cylinder or measuring pipette would be more appropriate due to the smaller volume.
1. Choose the appropriate graduated cylinder or pipette: For 18 mL, a 20 mL cylinder is typically useful, as it allows for accurate measurement from smaller markings.
2. Marking Intervals:
- Such glassware usually has markings at each 0.1 mL for high precision.
- More commonly, markings may be at every 0.5 mL or at every 1 mL.
3. Identifying the specific volume:
- Locate the marking for 10 mL.
- Locate the marking for 20 mL.
- Find the 18 mL marking directly labeled at two intervals below the 20 mL marking.
- If marked at every 0.5 mL, count from 16 mL through 16.5 mL, 17 mL, 17.5 mL, and then to 18 mL.
### Illustrations:
While I cannot physically draw a picture, here’s how you would conceptually visualize it:
For 128.7 mL:
```
| | | |
0 10 20 30
| | | |
120 125 130 135
^
|
Somewhere between these two lines is the 128.7 mL mark.
```
For 18 mL:
```
| |
0 5
| |
10 15
| | |
16.5 17 | 17.5
| | |
18......20.....
```
By following these markings, you can accurately measure out the desired volumes of water using the appropriate glassware.
