What gets through the filter? — answer key

1. Q07 · Practice

Model answer. The residue is sand because it remains on the paper after the liquid passes. Residue means material left after the separation process.

A full answer includes

• Sand is the retained material.
• Residue means material remaining after the process; here on the filter paper.

Also accept

• Sand left on the filter is the residue.

Watch for

• “Residue is the liquid in the receiver.” — The retained material is the residue. The liquid that passed is the filtrate.

2. Q08 · Practice

Model answer. The filtrate is the solution that has passed through the paper. It contains water and dissolved salt.

A full answer includes

• Filtrate is liquid or solution that passed through the filter.
• Contains water and dissolved salt.

Also accept

• Salt solution collected after passing through the filter.

Watch for

• “Filtrate is pure water.” — The ordinary paper retained sand, not dissolved salt. Both water and salt passed.

3. Q09 · Practice

Model answer. Chalk is the residue on the paper. It is an undissolved solid whose grains are retained while water passes.

A full answer includes

• Residue is chalk on the paper.
• Chalk remains undissolved and its grains are retained by the stated paper.

Also accept

• Retained insoluble chalk is the filtration residue.

Watch for

• “There cannot be a residue because there is no sand.” — Residue describes a product of the process, not a particular substance.

4. Q10 · Practice

Model answer. The filtrate is copper(II) sulfate solution: water and dissolved copper(II) sulfate pass through together. The retained chalk is not a dissolved component of that filtrate.

A full answer includes

• Filtrate is copper(II) sulfate solution.
• I named water and dissolved copper(II) sulfate.
• Both pass through ordinary paper while chalk grains are retained.

Also accept

• The collected solution contains solvent and solute, with the stated chalk removed.

Watch for

• “The filter removes the blue dissolved substance because it used to be solid.” — Its original physical state doesn’t make it an undissolved grain now. It is fully dissolved in the stated case.

5. Q11 · Practice

Model answer. Sand is retained; water and dissolved salt pass together. Filtration separates sand from salt solution, but doesn’t separate dissolved salt from water.

A full answer includes

• Sand retained; water and dissolved salt pass.
• Separates sand from salt solution, not salt from water.

Also accept

• Ordinary paper separates the stated insoluble solid from the solution.

Watch for

• “Filtration separates salt from water.” — The given dissolved salt passes with water; an additional method is needed to recover it.

6. Q12 · Practice

Options as numbered on the pupil sheet: 1 — Feed liquid still waiting to pass; 2 — Filtration residue; 3 — Collected filtrate.

Model answer. B is the residue and C is the collected filtrate. A is still feed liquid waiting above the paper, so it has not yet undergone the passage that defines collected filtrate.

A full answer includes

• B is residue; C is collected filtrate.
• A has not yet passed through the paper into the receiver.

Also accept

• The paper retains B; C has crossed the paper.

Watch for

• “Any liquid in a funnel is filtrate.” — Filtrate has passed through the filter; position alone doesn’t establish that.

7. Q13 · Practice

Model answer. Salt solution passes through. There are no undissolved salt grains for this ordinary paper to retain, so the plan doesn’t recover salt on the paper.

A full answer includes

• Water and dissolved sodium chloride pass into the filtrate.
• No salt is recovered as a retained solid by this filtration.
• Ordinary paper does not separate dissolved ions from the water in this case.

Also accept

• The collected filtrate is still salt solution; ordinary filtration does not achieve the intended separation.

Watch for

• “Filtering enough times will catch all the dissolved salt.” — Repeating the same unsuitable process doesn’t turn the dissolved ions into filterable crystals.

8. Q14 · Practice

Model answer. Pour smaller portions more slowly, keeping the liquid below the rim of correctly seated intact paper. The observed flow bypasses the paper and can carry unretained particles into the receiver, so the separation can’t be assumed successful.

A full answer includes

• I suggested slower/smaller pours, keeping liquid below the paper rim with properly seated intact paper.
• I explained bypass could carry unfiltered mixture into the receiver.

Also accept

• Stop, check the setup and repeat under the teacher's procedure so all collected liquid passes through the paper.

Watch for

• “Being in the receiver proves that all liquid crossed the paper.” — The question provides a bypass path. A vessel's position is not evidence of successful filtration.