Here's how to solve this problem. We need to use stoichiometry, which involves converting between masses and moles of substances using balanced chemical equations.

1. Write the balanced chemical equation:

Li₂CO₃ (s) → Li₂O (s) + CO₂ (g)

2. Calculate the molar mass of Li₂CO₃ and Li₂O:

* Li₂CO₃: (2 * 6.94 g/mol Li) + (12.01 g/mol C) + (3 * 16.00 g/mol O) = 73.89 g/mol

* Li₂O: (2 * 6.94 g/mol Li) + (16.00 g/mol O) = 29.88 g/mol

3. Convert the mass of Li₂CO₃ to moles:

20 g Li₂CO₃ * (1 mol Li₂CO₃ / 73.89 g Li₂CO₃) = 0.271 mol Li₂CO₃

4. Use the mole ratio from the balanced equation to find moles of Li₂O:

From the balanced equation, 1 mole of Li₂CO₃ produces 1 mole of Li₂O. Therefore, we have 0.271 mol of Li₂O.

5. Convert moles of Li₂O to grams:

0.271 mol Li₂O * (29.88 g Li₂O / 1 mol Li₂O) = 8.11 g Li₂O

Therefore, the mass of lithium oxide made from 20g of lithium carbonate is approximately 8.11 grams.