SME
Grade 6 Science · Problem type
Why cells stay small
Use this to see how a cube’s surface compares with its volume as it grows.
Table
Side
(cm)
Surface in cm² for each cm³
Surface area: 24 cm²
Volume: 8 cm³
This is an example. Type your own values to start a new problem.
Side
example · cm
Surface area
worked out (not typed) · cm²
Volume
worked out (not typed) · cm³
Surface in cm² for each cm³
worked out (not typed)
Formulas
6 × 2 × 2 = 24
6 faces × side × side = surface area
2 × 2 × 2 = 8
Side × side × side = volume
24 ÷ 8 = 3
Surface area ÷ volume = surface in cm² for each cm³
Assumptions
•
Food and oxygen enter a cell through its surface, and the whole inside uses them.
•
As a cube grows, its volume grows faster than its surface, so each cm³ gets less surface.
•
So living things grow by making more cells, not bigger ones.
Step-by-step
WE KNOW
Side: 2 cm
FIND
surface area, volume, surface in cm² for each cm³
Step 1 · Find surface area
6 × 2 × 2 = ?
6 faces × side × side = surface area
A cube has 6 square faces, each side × side.
Surface area = 24 cm²
Step 2 · Find volume
2 × 2 × 2 = ?
Side × side × side = volume
Side × side cubes fill one layer, and there are as many layers as the side.
Volume = 8 cm³
Step 3 · Find surface in cm² for each cm³
24 ÷ 8 = ?
Surface area ÷ volume = surface in cm² for each cm³
Share the surface among the cubic centimeters inside.
Surface in cm² for each cm³ = 3 (each cm³ gets 3 cm² of surface)
Check
Put the numbers back in. Both sides should match.
6 × 2 × 2 = 24 ✓
2 × 2 × 2 = 8 ✓
3 × 8 = 24 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
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