Heat will always flow from object A to object B if object B has a lower temperature.
Scientists define heat as thermal energy transferred between two systems at different temperatures that come in contact. Heat is written with the symbol q or Q, and it has units of Joules (J).
Heat is sometimes called a process quantity, because it is defined in the context of a process by which energy can be transferred. We don't talk about a cup of coffee containing heat, but we can talk about the heat transferred from the cup of hot coffee to your hand. Heat is also an extensive property, so the change in temperature resulting from heat transferred to a system depends on how many molecules are in the system.
Heat and temperature are two different but closely related concepts. Note that they have different units: temperature typically has units of degrees Celsius(°C) or Kelvin (K), and heat has units of energy, Joules (J). Temperature is a measure of the average kinetic energy of the atoms or molecules in the system. Temperature is also an intensive property, which means that the temperature doesn't change no matter how much of a substance you have (as long as it is all at the same temperature!).
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