Energy Transfer in Chemistry and Physics: Heat, Reactions, and States

What is heat?

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

What is heat transfer?

The movement of energy from a warmer object or substance to a colder one.

What is energy transfer?

The overall movement of energy between systems.

What is an exothermic reaction?

A process or reaction that releases energy into its surroundings, usually in the form of heat.

What is an endothermic reaction?

A process which absorbs energy from its surroundings, usually in the form of heat.

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 all the particles within a substance or system.

What is radiation?

The transfer of energy through space or a material medium in the form of electromagnetic waves.

What is convection?

The transfer of heat in a liquid or gas caused by differences in temperature and density.

What is conduction?

The transfer of heat between substances that are in direct contact.

Which way does energy/heat always flow?

It always moves from hot (more energy) to cold (less energy).

What are the three types of heat transfer?

1. Radiation: Sunlight heating the Earth. 2. Conduction: A metal spoon heating up in a hot pot of soup. 3. Convection: A home heating system circulating warm air.

How do flameless heaters and hand warmers transfer energy?

Both use exothermic reactions to create heat.

How does energy transfer from one substance to another?

Energy transfers when particles collide or touch, moving from the warmer object to the colder one until thermal equilibrium is reached.

What is Energy Transfer BIG Idea #1?

The greater the kinetic energy of the particles in a sample of matter, the hotter it is.

What is Energy Transfer BIG Idea #2?

Energy transfers between particles when they collide.

What is Energy Transfer BIG Idea #3?

Heat is energy transfer; heating a substance increases its kinetic energy.

What is Energy Transfer BIG Idea #4?

Energy always moves from higher energy (hot) to lower energy (cold).

Which bottle has a smaller average molecular kinetic energy and slower average speed?

Bottle 1

Why is there no change in temperature at thermal equilibrium?

Heat does not flow between objects in contact at the same temperature.

Which requires less heat to change temperature 1°C, silver or iron?

A given mass of silver requires less heat than an equal mass of iron.

What accounts for the different temperature increases in aluminum and iron when heated by 100 joules?

The specific heat of iron is less than that of aluminum.

What action will slow down the rate of temperature increase of water in a flask?

Adding more water at room temperature.

What explains the pressure increase in a gas as thermal energy increases?

The gas molecules move faster and strike the container walls more frequently.

What happens when a heated rock is placed in cooler water?

The heated rock loses heat to the container of water until they all reach the same final temperature.

Why does the smell of ammonia reach faster on a hot day?

Molecules move more rapidly at higher temperatures.

How should samples be selected to test if mass affects temperature change when heated?

Obtain samples of one substance, each with a different mass.

What increases in each sample of water when thermal energy is added?

Average speed of a molecule.

What does a rise in temperature inside a kitchen indicate?

An increase in the average kinetic energy of the air molecules.

What happens to food coloring in hot water compared to cold water?

The food coloring will spread out faster in the 85°C water than in the 15°C water.

Which scenario requires the greatest amount of heat?

Increasing the temperature of 10 kg of water from 10°C to 20°C.

What occurs when heat is added to a liquid?

The molecular motion in the liquid increases.

What makes nitrogen gas molecules move faster in a sealed container?

Transferring heat to the molecules.

What results from a temperature increase in a copper wire?

An increase in the motion of the copper particles.

Which temperature allows perfume to spread more easily?

25°C

What happens to perfume molecules at 25°C compared to 15°C?

At 25°C, they are moving faster.

Which substance's temperature will rise most with 1000 J of heat added?

Cooking oil.

What happens to the average molecular speed of a solid as it is heated?

The average molecular speed in the solid increases.

What type of block raises the temperature of water the most when heated?

The block with the greatest specific heat.

What describes the nitrogen gas in box A if it has twice the average speed of box B?

The nitrogen gas in box A has a greater temperature than the nitrogen gas in box B.

What must accompany an increase in average kinetic energy in a solid?

An increase in temperature.

What happens to the temperature of liquid 1 and liquid 2 when mixed?

After 5 minutes, liquid 2 will be on top; after 2 hours, they reach thermal equilibrium.

How does heat transfer occur between two liquids in a beaker?

Heat transfers by conduction and convection.

What is the effect of bond-breaking and bond-making on a reaction's energy?

Breaking bonds requires energy; forming bonds releases energy.

What causes a convection current to form in a fluid?

Heating causes expansion and less density, making it rise.

How does radiation differ from conduction and convection?

Radiation does not require a medium and can travel through a vacuum.

What happens to energy flow when two substances reach thermal equilibrium?

Heat stops flowing because there is no temperature difference.

What does high specific heat capacity mean for water?

Water requires more energy to change its temperature by 1°C.

What is the scientific difference between heat and temperature?

Heat is the transfer of thermal energy; temperature measures average kinetic energy.

Why are metal cooking pans paired with wooden or plastic handles?

Wood and plastic resist heat transfer, keeping handles cool.

How does the Greenhouse Effect warm a planet?

Greenhouse gases trap infrared radiation, preventing energy escape.

Why is boiling water considered an endothermic process?

Boiling requires heat absorption to break bonds between liquid particles.

What hazard is associated with activated MRE flameless heaters?

They produce flammable hydrogen gas in confined spaces.

What characterizes an exothermic reaction in terms of enthalpy?

An exothermic reaction has a negative enthalpy change (-ΔH).

What role do iron and salt play in a magnesium-based flameless heater?

They act as catalysts to accelerate the reaction.

How does the mass of a substance affect its total thermal energy?

Thermal energy depends on the amount of matter present.