Diffusion & Osmosis worksheet ANSWERS | Exams Biological Sciences ... - Free Printable

You’ve uploaded a completed “Diffusion and Osmosis Worksheet” with answers filled in. I’ll explain each section thoroughly so you understand *why* the answers are correct.

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## 1. How are the molecules moving? Write OSOMOSIS or DIFFUSION

> Key Definitions:
> - Diffusion: Movement of particles (molecules, ions, gases) from an area of high concentration to low concentration — can happen in air, water, or across membranes. No membrane needed.
> - Osmosis: A special type of diffusion — movement of water across a semi-permeable membrane from low solute concentration to high solute concentration (or high water concentration to low water concentration).

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a) Student smells gym sweat → DIFFUSION

- Smell molecules (odorants) move through the air from high concentration (near student) to low concentration (your nose).
- No membrane involved — just gas particles spreading out.
✔ Correct answer: D

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b) Fingers prune in bathtub → OSMOSIS

- Water enters skin cells because the bathwater is hypotonic (low solute) compared to inside cells.
- Water moves *into* cells → causes swelling → skin wrinkles.
✔ Correct answer: O

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c) Girl’s perfume fills the room → DIFFUSION

- Perfume molecules spread through air from high concentration (her clothes) to low concentration (air around you).
✔ Correct answer: D

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d) Salt kills slugs → OSMOSIS

- Salt creates a hypertonic environment outside slug’s body → water leaves slug cells via osmosis → dehydration → shriveling.
✔ Correct answer: O *(Note: The worksheet says “D” here — this is likely a mistake!)*

⚠️ Correction Needed: This should be OSMOSIS, not diffusion. Salt doesn’t diffuse into the slug — water diffuses *out* of the slug due to osmosis.

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e) Smell of neighbors’ grill → DIFFUSION

- Food odor molecules travel through air from grill (high conc.) to your nose (low conc.).
✔ Correct answer: D

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f) Gargling salt water for sore throat → OSMOSIS

- Salt water is hypertonic → draws water out of swollen throat cells via osmosis → reduces swelling → feels better.
✔ Correct answer: O

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g) Oxygen moves from lungs to blood → DIFFUSION

- Oxygen diffuses from alveoli (high O₂) into capillaries (low O₂) across thin membranes — still considered diffusion (passive transport of gas).
✔ Correct answer: D

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## 2. Use arrows to indicate direction of diffusion

> Diffusion = particles move from high concentration → low concentration

A) Box with many circles inside, few outside → Arrows point OUT of box

- More particles inside → net movement outward until equilibrium.
✔ Arrow drawn correctly.

B) Box with few circles inside, many outside → Arrows point IN to box

- More particles outside → net movement inward.
✔ Arrow drawn correctly.

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## 3. Net movement of sugar into/out of cell

> Sugar moves by diffusion — from high to low concentration.

Left cell: 1% sugar inside, 5% sugar outside → Sugar moves IN

- Higher concentration outside → sugar diffuses into cell.
✔ Arrow points up (into cell).

Middle cell: 3% sugar inside, 1% outside → Sugar moves OUT

- Higher concentration inside → sugar diffuses out.
✔ Arrow points down (out of cell).

Right cell: 1% inside, 1% outside → NO NET MOVEMENT

- Equal concentrations → no net diffusion.
✔ Correctly labeled “No Net”.

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## 4. Diffusion always causes particles to move from...

> From HIGH concentration → LOW concentration.

✔ Correctly filled: HIGH → LOW

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## 5. Does a cell use energy when molecules diffuse?

> NO — Diffusion is passive transport. It relies on kinetic energy of particles, not cellular energy (ATP).

✔ Correct answer: NO

> Explanation: “Diffusion is the passive movement of particles — energy does not need to be added for it to occur.”

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## ✔ Summary of Corrections & Notes:

| Question | Your Answer | Correct? | Notes |
|----------|-------------|----------|-------|
| 1d | D | ✘ | Should be O — osmosis causes water to leave slug cells |
| All others | As shown | ✔ | Well done! |

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## 💡 Key Takeaway:
- Diffusion = any particle moving down its concentration gradient (gas, liquid, solid).
- Osmosis = only water moving across a membrane toward higher solute concentration.

Let me know if you’d like diagrams or real-life analogies to reinforce these concepts!