Explanation

In thermodynamics, the part of the universe under study is referred to as the system.

Everything outside of this defined system is referred to as the surroundings or environment.

The system and its surroundings are separated by a boundary. 

Explanation

Thermal decomposition reactions are generally Endothermic.

They require a continuous input of heat energy to break the chemical bonds within a compound and separate it into two or more simpler substances. 

Energy input: The "thermal" part of the name refers to heat, which must be supplied to the reaction.

Breaking bonds: For a substance to decompose, its chemical bonds must be broken, a process that absorbs energy.

Lower temperature: Since the reaction absorbs energy from the surroundings, it causes the immediate area to become cooler. 

Explanation

In endothermic reactions, energy in the form of heat is taken in from the surroundings.

Examples include photosynthesis and melting of ice, where heat is absorbed to proceed.

In an exothermic reaction, energy (heat) is released/evolved to the surroundings.

Examples include combustion of fuels and respiration.

Explanation

When a substance is cooled slowly, only a limited number of nucleation sites are formed.

As a result, larger crystals are produced.

The better crystals tend to be obtained on slow cooling than on rapid cooling

• because rapid cooling induces the formation of many nucleation sites
• fast cooling yields small crystals.
  

Explanation

- Lead (Pb) is a stable element → its common isotope is not radioactive.

- Radium (Ra), Radon (Rn), and Uranium (U) are radioactive.

- Radioactive elements emit alpha, beta, or gamma radiation.

Explanation

- The symbol ⇌ shows that the reaction can proceed in both forward and reverse directions.

- Example: N₂ + 3H₂ ⇌ 2NH₃

- Such reactions do not go to completion and can reach equilibrium.

Explanation

- Organic chemistry is the branch of chemistry that deals with carbon compounds, especially hydrocarbons (compounds of carbon and hydrogen).

- Examples: Methane, Ethane, Propane.

Explanation

Ethanol has weaker intermolecular hydrogen bonding than water, so its molecules escape more easily.

This makes ethanol’s vapor pressure higher than that of water at the same temperature.

Explanation

A buffer contains a weak acid and its conjugate base; when a strong acid is added, the conjugate base reacts with H⁺ to form a weak acid.

This reaction resists a large change in pH, which is the main function of a buffer.

Explanation

An electrolytic cell uses electrical energy to drive a non-spontaneous chemical reaction, storing it as chemical energy.

In contrast, galvanic/Daniell cells convert chemical energy into electrical energy.