3.1.1 Physical and Chemical Change Flashcards
(22 cards)
What is a chemical change?
A process in which one or more substances are transformed into new substances with different chemical properties.
What is a physical change?
An alteration in the particle structure of a substance that does not change its chemical composition.
What happens to the composition of a substance during a physical change?
No new substances are formed; the composition remains the same.
Are most physical changes reversible?
Yes, most physical changes can be reversed.
List three examples of physical changes.
- Melting ice to water
- Boiling water to steam
- Freezing water to ice
What is an example of a physical change involving water?
The boiling or evaporation of water.
What is the equation representing the evaporation of water?
H₂O(l) ⇌ H₂O(g)
What occurs during the freezing of water?
The average distance between molecules decreases, resulting in stronger intermolecular forces.
What is the definition of a chemical reaction?
A process in which original substances are converted into one or more new substances.
What is a key characteristic of chemical changes?
They often involve the formation of new substances.
Are chemical changes usually reversible?
No, many chemical changes are essentially irreversible.
What are exothermic reactions?
Chemical reactions that release energy in the form of heat.
What is an indicator of a chemical reaction?
Change in color, gas production, formation of a precipitate, change in temperature, odour production.
Fill in the blank: In a chemical change, the bonds between atoms in molecules are ______.
broken and new ones are formed.
What is one example of a chemical change?
The oxidation of iron to form rust.
What is the equation representing the formation of rust?
4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)
What should you consider when evaluating if a change is chemical or physical?
Whether the substance itself has transformed into something new.
What are the energy changes during chemical changes characterized by?
Endothermic or exothermic reactions.
What happens during endothermic reactions?
They absorb heat from their surroundings.
What is a key difference between physical and chemical changes?
Chemical changes alter the chemical composition, while physical changes do not.
What happens to energy during physical changes?
Energy is either absorbed or released depending on the state change.
True or False: The amount of energy change during chemical reactions is generally less than during physical changes.
False.
