Heat Transfer & Energy Concepts in Physics: Types, Reactions, and Applications

What is heat?

The transfer of energy between objects that are at different temperatures.

What is heat transfer?

The movement of energy from a warmer object to a cooler object.

What is energy transfer?

The process by which energy moves between systems or substances, such as through particle collisions.

How does energy transfer from one substance to another?

Primarily through conduction when particles collide or are touching.

What is an exothermic reaction?

A process or reaction that releases energy (usually heat or light) into its surroundings.

Why does an exothermic reaction feel hot?

More energy is released when forming product bonds than it took to break reactant bonds.

What is an endothermic reaction?

A process or reaction that absorbs energy from its surroundings.

Why does an endothermic reaction feel cold?

It takes more energy to break reactant bonds than is released when forming product bonds.

What is temperature?

A measure of the average kinetic energy of the particles within a substance.

What is thermal energy?

The total kinetic energy of the random motion of atoms and molecules within a substance or system.

If a cup and a bucket of water are at the same temperature, which has more thermal energy?

The bucket.

What is radiation?

The transfer of energy through space or a material medium in the form of electromagnetic waves without the need for direct contact.

Give an example of radiation.

Feeling the heat from an open fire or sunlight warming the Earth.

Does radiation require matter to transfer heat?

No.

What is convection?

The transfer of heat within liquids or gases caused by differences in temperature and density.

Give an example of convection.

A household heating system or a hot air balloon rising.

What causes the circular 'current' in convection?

Heated fluid expands and becomes less dense, causing it to rise.

What is conduction?

The transfer of heat through direct contact when particles of matter collide.

Give an example of conduction.

A metal spoon heating up in a hot pot of soup.

In which state of matter does conduction work most effectively?

Solids.

Which way does energy/heat always flow?

From higher to lower temperature.

What are the three types of heat transfer?

Conduction, convection, radiation.

How do flameless heaters transfer energy to warm up substances?

Exothermic chemical reactions.

What happens to the speed of two particles when a fast one collides with a slow one?

The fast one slows down, and the slow one speeds up.

What is thermal equilibrium?

A state where two objects in contact reach the same temperature with no net change in thermal energy.

What is a thermal conductor?

A material that transfers thermal energy very well.

What is a thermal insulator?

A material that resists the flow of heat.

Why is boiling considered an endothermic physical process?

Energy must be absorbed to break the bonds between liquid particles to turn them into a gas.

What does a negative enthalpy change (-ΔH) mean?

The system has released heat energy to the surroundings (exothermic reaction).

In engineering, what are 'criteria'?

The requirements or goals that a design must meet to be successful.

In engineering, what are 'constraints'?

The limitations placed on a design.

What is specific heat capacity?

The energy needed to change the temperature of 1 kg of a substance by 1°C.

Where is chemical energy stored?

In the bonds that hold atoms together in chemical substances.

Why is the burning of fuel (combustion) exothermic?

It converts stored chemical energy into heat and light that is released into the environment.

What type of reaction is a MRE?

Exothermic reaction.

In a MRE, what does the pad in the bag contain?

Magnesium powder, iron powder, and table salt.

What happens in the MRE's exothermic reaction?

The water dissolves into the water and the powders burn out instantly and release heat.

What happens once the heater gets hot in a MRE?

The heater transfers heat to the food.

What kind of transfer of energy is the MRE?

Conduction.

What happens at particle level in an MRE?

Fast particles hit the slow ones.

What happens to the particles in an MRE?

The fast ones slow down and the slow ones speed up.