Must Know Units and Conversions for GCSE Chemistry!

Understanding units is a fundamental aspect of mastering GCSE Chemistry. Accurate measurement and conversion of units are crucial for conducting experiments, analysing data, and understanding scientific concepts. However, many students find units challenging due to the variety of measurements and the need to convert between them. But—DO NOT FEAR! This cheat sheet is designed to simplify the process and help you remember key conversions easily.

Volume is measured in cm³, dm³ or m³

Volume is a crucial measurement in chemistry, frequently used when dealing with gases, liquids, and solutions. Accurate volume measurements are needed for preparing solutions, determining reactant quantities, and conducting experiments involving gases under varying conditions. Volume is measured in cubic centimetres (cm³), cubic decimetres (dm³), and cubic metres (m³).

Historical Context:

The concept of volume dates back to ancient civilisations that needed to measure quantities of agricultural produce, liquids, and building materials. With the advent of modern science, precise volume measurement became very extremely important for conducting experiments.

1 m³ = 1000 dm³ = 1,000,000 cm³

Tip: If you find it hard to remember, try to remember “MDC, 036”. The numbers 036 stand for the number of zero’s there are for each unit!

Example 1: convert cm³ to m³

How do you convert 500,000 cubic centimetres (cm³) to cubic meters (m³)?

500,000 cm³ = Y m³

If we know that 1,000,000 cm³=1 m³, we can write:

• 500,000 cm³ = Y m³
• 1,000,000 cm³ = 1 m³

Dividing the top equation by the bottom, we get:

Then:

So:

Example 2: convert cm³ to dm³

How do you convert 500,000 cubic centimetres (cm³) to cubic decimeters (dm³)?

500,000 cm³ = Z dm³

So again, if we know that 1,000,000 cm³=1000 dm³, we can write:

• 500,000 cm³ = Z m³
• 1,000,000 cm³ = 1000 dm³

Dividing the top equation by the bottom, we get:

Then:

So:

Note: When constructing the equations, you can only divide numbers with the same units. In the examples above, cm³ is divided by cm³, and dm³ is divided by dm³. This means that you can cancel the units and come out with the correct numbers.

Temperature is measured in kelvin (K) and ⁰C. 

Temperature is another critical measurement in chemistry, influencing reaction rates and states of matter. It is measured in kelvin (K) and degrees Celsius (°C). Understanding temperature scales is essential for interpreting experimental data and predicting the behaviour of substances under different conditions.

Historical Context:

The Kelvin scale, named after Lord Kelvin, is an absolute temperature scale used predominantly in scientific settings. It starts at absolute zero. The Celsius scale, created by Anders Celsius, is widely used in everyday applications and is based on the freezing and boiling points of water.

273K = 0⁰C

Let’s try an example!

What is 258 Kelvin in degrees Celcius?

258K = ? ⁰C

If we know that 273K = 0⁰C, 

Then 258K - 273K = -15⁰C

Note: one way of thinking about this is that 258 is 15 less than 273, so it must also be 15 less than 0⁰C, making it -15⁰C.

Mass is measured in milligrams (mg), grams (g), kilograms (kg) and in tonnes

Mass is measured in milligrams (mg), grams (g), kilograms (kg), and tonnes. It quantifies the amount of substance involved in chemical reactions, impacting reaction yields and concentrations. Accurate mass measurements are fundamental for preparing reactants, and ensuring reproducibility in experiments.

Historical Context:

The gram was originally defined as the mass of one cubic centimeter of water at 4°C. Today, it remains the base unit of mass in the metric system, essential for scientific accuracy. The kilogram and tonne are larger units used for more substantial quantities, reflecting the mass of objects from small samples to industrial quantities.

1 tonne = 1,000 kg 

1 kg = 1,000 g 

1g = 1,000 mg 

Pressure is measured in pascals (Pa) and kilopascals (kPa) 

1 kPa = 1000 Pa

Pressure is measured in pascals (Pa) and kilopascals (kPa). These units are important for measuring gas behaviour, described by the laws of Boyle, Charles, and Avogadro (not Avocado!). Accurate pressure measurements are crucial for understanding gas reactions, behavior under varying conditions, and applications such as chemical engineering and meteorology.

Historical Context:

The pascal, named after Blaise Pascal, a pioneer in fluid mechanics, is the SI unit of pressure. It reflects the force applied per unit area and is used universally in scientific research and applications. The kilopascal, a larger unit, is often used in practical scenarios to simplify measurements.

Now put yourself to the test!

Here are 10 practice questions so you can master your new unit conversion skills:

1. 25 cm³ into dm³
2. 0.05 m³ into cm³
3. 26 ⁰C into K
4. 240 K into ⁰C
5. 310 mg into kg
6. 200 g into kg
7. 250 g into tonnes
8. 1500 Pa into kPa
9. 60 kPa into Pa
10. 70 dm³ into m³

Answers: