Liquids are heated by conduction and radiation.

Answer

### Step-by-Step Solution:

1. **Understanding Heat Transfer Modes**:
- Heat transfer occurs through three main modes: conduction, convection, and radiation.
- Conduction occurs in solids, convection occurs in liquids and gases, and radiation can occur in a vacuum.

2. **Conduction**:
- Conduction is the process where heat is transferred through molecular movement in solids.
- Example: When one end of a metal rod is heated, the heat travels along the rod, causing the other end to become warm due to the movement of molecules.

3. **Convection**:
- Convection is the process of heat transfer in fluids (liquids and gases) where warmer parts of the fluid rise and cooler parts sink.
- Example: In a cup of tea, the heat from the tea transfers to the surrounding air, causing the tea to cool down. This is a natural process where the heat moves from a higher temperature (the tea) to a lower temperature (the surrounding air).

4. **Radiation**:
- Radiation is the transfer of heat in the form of electromagnetic waves and does not require a medium.
- Example: The sun emits rays that travel through space and warm the Earth. This process does not involve any physical medium.

5. **Conclusion**:
- In liquids, the primary mode of heat transfer is convection. Conduction and radiation do not effectively occur in liquids.
- Therefore, the statement "Liquids are heated by conduction and radiation" is **false**.