Contents
Key Stage 2
Meaning
Gas is a state of matter that can change size and shape to fit any container.
About Gases
- Most gases are invisible but we can feel them.
- When the air moves we call it the wind.
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Gases can be squashed into a smaller size. |
Examples of gas materials:
- Air (A mixture of gases, mostly nitrogen and oxygen)
- Steam
Key Stage 3
Meaning
Gas is a State of Matter in which the particles are separated by large distances and can move freely.
About Gases
Gas can be squashed into a smaller size because the particles are spread apart. |
Key Stage 4
Meaning
Gas is a State of Matter in which the particles are separated by large distances and can move freely.
About Gases
- When a substance is in its gaseous state it is always less dense than in its liquid or solid state due to the particles in a gas being spread far apart from each other.
- A substance which is gaseous at room temperature has a smaller force of attraction between particles than a substance which is liquid or solid at room temperature.
Particle Diagram | Particle Arrangement | Property |
Particles are free to move in all directions. | Gases fit the size of their container. | |
Gases fit the shape of their container. | ||
Convection happens most easily in gases. | ||
Particles are spread apart. | Gases can be compressed into a smaller volume. | |
Sound passes through gases slower than liquids and solids. | ||
Thermal Conduction is very poor in a gases. |
Gas Volume and Mass
- At Standard Temperature and Pressure (20°C and 101,000Pa) the volume of one mole of gas is 24 dm3.
- The volume of gas required or produced in a chemical reaction can be calculated from the mass of the gas and its Relative Formula Mass.
Example Calculations
Calculate the volume of 4g of Hydrogen gas. | Calculate the volume of 8g of Oxygen gas. | Calculate the volume of 20g of Methane gas. |
1.Find the Relative Formula Mass of the gas.
Chemical Formula of Hydrogen = H2 Relative Atomic Mass of Hydrogen = 1g Relative Formula Mass of H2 = 2g |
1.Find the Relative Formula Mass of the gas.
Chemical Formula of Oxygen = O2 Relative Atomic Mass of Oxygen = 16g Relative Formula Mass of O2 = 32g |
1.Find the Relative Formula Mass of the gas.
Chemical Formula of Methane = CH4 Relative Atomic Mass of Hydrogen = 1g
Relative Formula Mass of CH4 = 16g |
2. Calculate the number of moles of gas.
1 mole = 2g No. Moles = \(\frac{Mass}{M_r}\) No. Moles = \(\frac{4}{2}\) No. Moles = 2mol |
2. Calculate the number of moles of gas.
1 mole = 32g No. Moles = \(\frac{Mass}{M_r}\) No. Moles = \(\frac{8}{32}\) No. Moles = 0.25 mol |
2. Calculate the number of moles of gas.
1 mole = 16g No. Moles = \(\frac{Mass}{M_r}\) No. Moles = \(\frac{20}{16}\) No. Moles = 1.25 mol |
3. Find the volume in dm3.
Volume = 24 x (number of moles) Volume = 24 x (2) Volume = 48dm3 |
3. Find the volume in dm3.
Volume = 24 x (number of moles) Volume = 24 x (0.25) Volume = 6dm3 |
3. Find the volume in dm3.
Volume = 24 x (number of moles) Volume = 24 x (1.25) Volume = 30dm3 |
Calculate the mass of 12dm3 of Hydrogen gas. | Calculate the mass of 36dm3 of Nitrogen gas. | Calculate the mass of 18dm3 of Ethane gas. |
1.Find the Relative Formula Mass of the gas.
Chemical Formula of Hydrogen = H2 Relative Atomic Mass of Hydrogen = 1g Relative Formula Mass of H2 = 2g |
1.Find the Relative Formula Mass of the gas.
Chemical Formula of Nitrogen = N2 Relative Atomic Mass of Nitrogen = 14g Relative Formula Mass of N2 = 28g |
1.Find the Relative Formula Mass of the gas.
Chemical Formula of Ethane = C2H6 Relative Atomic Mass of Hydrogen = 1g Relative Atomic Mass of Carbon = 12g Relative Formula Mass of C2H6 = 30g |
2. Calculate the number of moles of gas.
Volume = 24 x (number of moles) 12 = 24 x (number of moles) Number of moles = 12/24 Number of moles = 0.5 |
2. Calculate the number of moles of gas.
Volume = 24 x (number of moles) 36 = 24 x (number of moles) Number of moles = 36/24 Number of moles = 1.5 |
2. Calculate the number of moles of gas.
Volume = 24 x (number of moles) 12 = 24 x (number of moles) Number of moles = 18/24 Number of moles = 0.75 |
3. Find the mass of gas from the number of moles.
No. Moles = \(\frac{Mass}{M_r}\) 0.5 = \(\frac{Mass}{2}\) Mass = \(0.5\times2\) Mass = 1g Volume = 48dm3 |
3. Find the mass of gas from the number of moles.
No. Moles = \(\frac{Mass}{M_r}\) 1.5 = \(\frac{Mass}{28}\) Mass = \(1.5\times28\) Mass = 42g |
3. Find the mass of gas from the number of moles.
No. Moles = \(\frac{Mass}{M_r}\) 0.75 = \(\frac{Mass}{30}\) Mass = \(0.75\times30\) Mass = 22.5g |