Starter quiz
- Which of the following is a pure substance made of two or more elements chemically combined?
- Mixture
- Compound ✓
- Solution
- Element
-
- If an oxygen molecule consists of two oxygen atoms, what is its relative formula mass (Mr)?
- 16.0
- 8.0
- 32.0 ✓
- 240
-
- Which of the following best describes a mole?
- A unit measuring the purity of a substance.
- A unit representing a certain number of particles. ✓
- A unit measuring the volume of a gas.
- A unit representing the density of a substance.
-
- To convert 50 grams of water to moles of water (Mr of 18.0), you would:
- Multiply 50 by 18.0.
- Divide 50 by 18.0. ✓
- Divide 18.0 by 50.
- Divide 18.0 by Avogadro's number.
- Divide 50 by Avogadro's number.
-
- What does the term "percent composition" refer to in chemistry?
- The percentage of a sample that is water.
- The relative amounts of each element in a compound. ✓
- The concentration of a solution.
- The ratio of solute to solvent in a mixture.
-
- Calculate the moles of methane (CH₄) in a sample of 55.2 grams. Give your answer to 2 significant figures.
- '3.5' ✓
Exit quiz
- What does one mole of any substance contain?
- 6.02 × 10²³ particles ✓
- 6.02 × 10²⁰ things
- 1,000 particles
- The mass of the substance in grams
-
- 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.
- Why is it important to choose the appropriate apparatus for measurements in chemistry?
- To complete experiments faster.
- To reduce measurement uncertainty. ✓
- To use fewer chemicals.
- To make cleaning up easier.
-
- Which of the following best describes the term "accuracy"?
- The precision of the measurement tools.
- The repeatability of measurements.
- How close a measured value is to the true value. ✓
- The number of significant figures in a measurement.
-
- 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.
- '117 g' ✓
- Calculate the number of SO₄²⁻ ions in 34 g of Al₂(SO₄)₃. The answer is ______ × 10²³. Give your answer to 3 significant figures.
- '1.79' ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- Manipulating apparatus correctly ensures both accurate results and safety in the lab.
- Interconversion between units like grams, moles, volume, density & particles is fundamental in chemical calculations.
- Successful interconversion is only possible if the units match.
- Using the appropriate apparatus for a required measurement can help to reduce uncertainty.
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.
Keywords
Mole - A mole of 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.