Identify whether the following processes are exothermic or...

Identify whether the following processes are exothermic or endothermic. Is the sign on $q_{\text {sys }}$ positive or negative? (a) combustion of methane (b) melting of ice (c) raising the temperature of water from $25^{\circ} \mathrm{C}$ to $100^{\circ} \mathrm{C}$ (d) heating $\mathrm{CaCO}_{3}(\mathrm{s})$ to form $\mathrm{CaO}(\mathrm{s})$ and $\mathrm{CO}_{2}(\mathrm{g})$

Identify whether the following processes are exothermic or endothermic. Is the sign on $q_{\text {sys }}$ positive or negative?
(a) combustion of methane
(b) melting of ice
(c) raising the temperature of water from $25^{\circ} \mathrm{C}$
to $100^{\circ} \mathrm{C}$
(d) heating $\mathrm{CaCO}_{3}(\mathrm{s})$ to form $\mathrm{CaO}(\mathrm{s})$ and $\mathrm{CO}_{2}(\mathrm{g})$

Key Concepts

Exothermic Process

An exothermic process releases heat energy to its surroundings, which results in a decrease in the system’s internal energy. In such processes, the sign on q for the system is negative because energy is being lost as heat.

Endothermic Process

An endothermic process absorbs heat energy from its surroundings, causing an increase in the system’s internal energy. In these processes, the sign on q for the system is positive as it gains energy.

Sign Conventions in Thermochemistry

The sign convention for heat (q) in thermochemistry is crucial for understanding energy flow. A positive q indicates heat absorbed by the system, while a negative q indicates heat released by the system. This provides a standardized way to analyze and compare thermal changes during physical and chemical processes.

Phase Changes and Temperature Variations

Phase changes and temperature variations involve energy exchange with the surroundings. Processes that involve breaking intermolecular bonds, such as melting, are usually endothermic (heat absorbed), whereas processes that form new bonds or release energy, like combustion, are exothermic (heat released).

Transcript

00:01 Hey guys, so this question we first need to know what an exothermic and what an endothermic reaction are.

00:06 So an exothermic reaction is energy transfer from the system to surroundings, and the q system is less than zero.

00:14 In an endothermic reaction, the energy is transferred from the surroundings to the system, and the q system is greater than zero.

00:24 So for the first part of the question, we're going to be discussing the combustion of methane, and then we'll be looking at ice melting, temperature of water raising, and heating, c -a -c -o -3.

00:45 So if we just look at all of these before we try to come up with an answer, we can kind of determine a pattern, which will help us answer the question a little bit better.

00:55 So i'm going to start with b because it's a little more straightforward.

01:01 This is just melting up ice.

01:04 So when ice melts, it's melting because it's getting warmer.

01:09 So it's being raised above that freezing temperature.

01:14 So basically, it's just water getting warmer.

01:22 And then for the second part of the question, or for the third part of the question, sorry, it's literally just talking about the temperature of water raising.

01:35 So it's essentially the same thing, water getting warmer.

01:41 So right there, we know that b and c are going to have the same answer because it's essentially describing the same thing.

01:48 And then for d, we're talking about heating a compound to form a solid and a gas...

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