New
New
Year 10
OCR
Higher

Representations of a mole (RAM 1 d.p.)

I can accurately represent a set number of moles of various substances.

New
New
Year 10
OCR
Higher

Representations of a mole (RAM 1 d.p.)

I can accurately represent a set number of moles of various substances.

Lesson details

Key learning points

  1. Manipulating apparatus correctly ensures both accurate results and safety in the lab.
  2. Interconversion between units like grams, moles, volume, density & particles is fundamental in chemical calculations.
  3. Successful interconversion is only possible if the units match.
  4. Using the appropriate apparatus for a required measurement can help to reduce uncertainty.

Keywords

  • Mole - something is 6.02 × 10²³ of it. The mass of a mole of a substance is its relative mass expressed in grams.

  • Apparatus - is a piece of equipment that is designed for a particular use.

  • Interconversion - is the ability to change between two units of measurement

  • Accuracy - refers to how close a measured value is to the true or standard value.

  • Uncertainty - is the range of measurements within which the true value can be expected to be found. On apparatus, it is half the value of one resolution marking.

Common misconception

Pupils mistake that the same mass of different substances = the same number of particles.

This activity reinforces the mathematical relationship between relative formula mass of a substance, the number of particles present and the mass measured in the lab.

Consider extending the lesson with added challenge - include gases in the presentation. Challenge pupils to justify their equipment choice and relate it to accuracy of their 'show'.
Teacher tip

Equipment

balance, weigh boat or equivalent, spatula, measuring cylinders, dropping pipettes, syringes, water, ethanol, sodium chloride, zinc, sodium hydrogencarbonate, sulfur, beakers, boiling/test tubes

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
Which of the following is a pure substance made of two or more elements chemically combined?
Mixture
Correct answer: Compound
Solution
Element
Q2.
If an oxygen molecule consists of two oxygen atoms, what is its relative formula mass (Mr)?
16.0
8.0
Correct answer: 32.0
240
Q3.
Which of the following best describes a mole?
A unit measuring the purity of a substance.
Correct answer: A unit representing a certain number of particles.
A unit measuring the volume of a gas.
A unit representing the density of a substance.
Q4.
To convert 50 grams of water to moles of water (Mr of 18.0), you would:
Multiply 50 by 18.0.
Correct answer: Divide 50 by 18.0.
Divide 18.0 by 50.
Divide 18.0 by Avogadro's number.
Divide 50 by Avogadro's number.
Q5.
What does the term "percent composition" refer to in chemistry?
The percentage of a sample that is water.
Correct answer: The relative amounts of each element in a compound.
The concentration of a solution.
The ratio of solute to solvent in a mixture.
Q6.
Calculate the moles of methane (CH₄) in a sample of 55.2 grams. Give your answer to 2 significant figures.
Correct Answer: 3.5

6 Questions

Q1.
What does one mole of any substance contain?
Correct answer: 6.02 × 10²³ particles
6.02 × 10²⁰ things
1,000 particles
The mass of the substance in grams
Q2.
Order the following steps in the process of converting grams to moles.
1 - Measure the mass of the substance.
2 - Calculate the substance's relative formula mass.
3 - Divide the mass of the substance by its relative formula mass.
Q3.
Why is it important to choose the appropriate apparatus for measurements in chemistry?
To complete experiments faster.
Correct answer: To reduce measurement uncertainty.
To use fewer chemicals.
To make cleaning up easier.
Q4.
Which of the following best describes the term "accuracy"?
The precision of the measurement tools.
The repeatability of measurements.
Correct answer: How close a measured value is to the true value.
The number of significant figures in a measurement.
Q5.
If the relative formula mass of sodium chloride (NaCl) is 58.5, what is the mass of 2 moles of NaCl? Give the answer to 3 significant figures.
Correct Answer: 117 g, 117 grams, 117
Q6.
Calculate the number of SO₄²⁻ ions in 34 g of Al₂(SO₄)₃. The answer is × 10²³. Give your answer to 3 significant figures.
Correct Answer: 1.79