3 (a) Carbon dioxide is one of the gases in the Earth's atmosphere - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2019 - Paper 1

Factor 1: Human Activity - The burning of fossil fuels, deforestation, and industrial processes release significant amounts of carbon dioxide into the atmosphere, contributing to higher concentrations.

Factor 2: Natural Processes - Natural activities such as volcanic eruptions and oceanic absorption of CO₂ can influence the levels of carbon dioxide, leading to variations.

Carbon dioxide has a low boiling point primarily due to the weak intermolecular forces (Van der Waals forces) present between its molecules. These forces require less energy to overcome, allowing CO₂ to change from liquid to gas at low temperatures.

To find the number of molecules in 0.11 g of carbon dioxide, use the following steps:

1. Calculate the number of moles:

   $\text{Number of moles} = \frac{\text{mass}}{\text{molar mass}} = \frac{0.11 \text{ g}}{44 \text{ g/mol}} = 0.0025 \text{ mol}$

2. Use Avogadro's number to find the number of molecules:

   $\text{Number of molecules} = 0.0025 \text{ mol} \times 6.02 \times 10^{23} \text{ molecules/mol} = 1.51 \times 10^{21} \text{ molecules}$

Thus, the answer to two significant figures is approximately $1.5 \times 10^{21}$ molecules.