1. Step 1 in the Road to Understanding Chemistry
Measurements & Ratios
Step 1 in the Road to Understanding Chemistry

2. Measuring with a Metric Ruler1 2 3 4 5 cm 6
3.20
3.30
Length of Bar 3.2 cm + estimate between marks = 3.23 cm
Special notes:
Always start on the zero line, not the end of the ruler
Always write down the last used number on the ruler
Estimate 1 digit between mm lines (if it is exactly on the line then that next digit is 0)

3. Sample Measurements Let’s Practice to check your skillscm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Length of Bar estimate = cm cm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Length of bar cm = cm (right on line)
Let’s Practice to check your skills

4. Using Length to Calculate Volume
The amount of space an object takes up
Volume Units: cm3 (cmcmcm), cubic cm (cc), mL
All of the above units are equal
May also use any distance unit that is cubed
Formulas
Prism Volume = Base Area  prism height*
For a rectangular prism (box) this means lwh*
For a triangular prism this means ½  b  h  h*
For a cylinder this means   r2  h*
Sphere Volume = 4/3radius3 or 4/3circle arear

5. Practice Volume of Rectangular Prism (Box)
Box Dimensions
Calculations
Side measurements
l = 4 m,
w= 2 m,
h = 3 m
V= lwh
V = 4 m  2 m  3 m
V = 24 mmm
V=24 m3
Side A
3 m
2 m
4 m

6. Practice Volume of Rectangular Prism (Box)
Note: All sides must be in the same unit
Box Dimensions
Calculations
Get sides in same unit (convert all to cm)
l = 1 m = 100 cm,
w= 30 cm (keep this one),
h = 400 mm = 40 cm
V= lwh
V = 100 cm  30 cm  40 cm
V = cmcmcm
V= cm3
Side A
400 mm
30 cm
1 m
Let’s Practice

7. Practice Volume of Cylindrical Prism (Box)
Note: All measurements must be in the same unit
Box Dimensions
Calculations
r = 10 cm
h = 5 cm
V= base area · height
V =  · r2 · h
V = 3.14 · (10 cm)2· 15 cm
V= 3.14 · 100 · 15 cm2·cm
V = 4710 cm3
10 cm
15 cm
Let’s Practice

8. Practice Volume of Sphere (Ball)
Note: Moving to circles
Box Dimensions
Calculations
r = 5 cm
V= 4/3 ·  · r3
V = 4/3 · 3.14 · (5 cm)3
V = 4/3 · 3.14· 125 cm3
V = cm3
5 cm
C = 31.4 cm
How would you solve this if all you had was a C = 31.4 cm

9. Practice Volume of Sphere (Ball)
What happens if you can’t measure radius?
Box Dimensions
Calculations
C = 31.4 cm
First find r
r =C/2 = 31.4 cm/6.28 = 5 cm
Plug r into the formula
V = 4/3 · 3.14 · (5 cm)3
V = 4/3 · 3.14· 125 cm3
V = cm3
5 cm
C = 31.4 cm
Let’s Practice

10. Liquid Volume Measuring
always use a graduated cylinder to measure liquid volume
do NOT use a beaker or flask to accurately measure liquid volume (only approximate )
estimate one decimal place beyond what is marked on the graduated cylinder (like ruler)
Watch your scale markings (what is each line worth)
Meniscus: curved surface of a liquid in a tube
Measure the liquid at the bottom center of the lower curve of the meniscus (bdc) at eye level
Note: some plastic cylinders don’t curve the water

11. Check your skills Measure liquid level here Let’s Practice
Activity: Take a graduated cylinder, put some water in it & draw in your notes what the top of the water looks like in the cylinder
Measure liquid level here
Let’s Practice

12. Using Liquids to Measure Volume
Fill
Displacement
If the object is hollow you can fill the object with water and measure the amount of liquid
What do you do about the side thicknesses?
If the object is solid or can’t hold water
Fill a container to the brim with water
Put object in the water
Measure the water that comes out of the container
What do you do about floating objects?