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๐ฌ Think about it
Blood can be spun apart like a suspension, yet its cells are too small to see, like a solution. So which is it? Neither — it is something in between, called a colloid. Let us understand colloids.
What is a colloid?
Colloid
1–1000 nm
bigger than a solution, smaller than a suspension
Never settles
stays evenly spread
↓
Colloid
= particles too small to see, but big enough to
scatter light
. Blood, milk, ice cream.
- It is a mixture that is neither a true solution nor a true suspension.
- Its particles are bigger than in a solution but smaller than in a suspension.
- The particles do not settle over time.
- They stay uniformly spread, as in a solution.
Example:
Blood, milk, tomato sauce and ice cream are colloids.
How do solutions, colloids and suspensions differ in particle size?
How do the three types of mixture differ?
Mixtures
Grouped by particle size
1. Solution
Under 1 nm
No Tyndall effect
No Tyndall effect
Example:
Salt solution
Sugar water
2. Colloid
1 to 1000 nm
Shows Tyndall
Shows Tyndall
Example:
Milk
Blood
Ice cream
3. Suspension
Over 1000 nm
Settles out
Settles out
Example:
Chalk in water
Muddy water
| Mixture | Particle size | Do particles settle? |
|---|---|---|
| Solution | Less than 1 nm | No |
| Colloid | 1–1000 nm | No |
| Suspension | More than 1000 nm | Yes |
- A solution has the smallest particles (less than 1 nm).
- A colloid has medium particles (1–1000 nm).
- A suspension has the largest particles (more than 1000 nm).
Important Points
- A colloid sits between a solution and a suspension.
- Its particles do not settle and stay evenly spread.
- Particle size: solution < colloid < suspension.
๐ Bridging Science and Society
- Donating blood saves lives in emergencies and surgeries.
- Donated blood is tested and separated into components like plasma and cells.
- These are stored in blood banks and supplied when needed.
- The body naturally replaces donated blood within a few weeks.
โ Test Yourself
-
Is blood a solution, suspension or colloid?
View Answer
A colloid. -
Which mixture has the largest particles?
View Answer
A suspension (more than 1000 nm). -
Do colloid particles settle over time?
View Answer
No — they stay evenly spread out.
Important Definitions
- Colloid — a mixture whose particle size is between that of a solution and a suspension, and whose particles do not settle.
๐ NCERT Question 10 — Blood is an example of
Blood is an example of a colloidal mixture. (i) What would happen if blood behaved like a true suspension inside the body? (ii) In a blood sample, identify the dispersed phase and the dispersion medium.
View Answer →
๐ NCERT Question 3 — A mixture can be categorised
A mixture can be categorised as a solution, a suspension, or a colloid, each possessing distinct properties. Utilise the words or phrases provided in the box to fill in the Table 5.2. Words and phrases may be used more than once.
Words and Phrases
Large-sized particles; Particles remain evenly distributed; Small-sized particles (less than 1 nm diameter); Moderate-sized particles (1 – 1000 nm); Settles down when left undisturbed (more than 1000 nm in diameter); Does not settle down; Scatters light; Separates by filtration; Transparent; Salt solution; Milk; Sand in water; Smoke; Heterogeneous mixture; Cannot be separated by filtration; Mud; Butter; Brass.
Complete the Table 5.2.
View Answer →
Words and Phrases
Large-sized particles; Particles remain evenly distributed; Small-sized particles (less than 1 nm diameter); Moderate-sized particles (1 – 1000 nm); Settles down when left undisturbed (more than 1000 nm in diameter); Does not settle down; Scatters light; Separates by filtration; Transparent; Salt solution; Milk; Sand in water; Smoke; Heterogeneous mixture; Cannot be separated by filtration; Mud; Butter; Brass.
Complete the Table 5.2.
