Starter quiz
- Which of the following is a 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
- 8
- 32 ✓
- 24
-
- 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), you would ...
- multiply 50 by 18.
- divide 50 by 18. ✓
- divide 18 by 50.
- divide by Avogadro's number.
- multiply 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
- 1000 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 and 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 - 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 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.