Properties & Definitions
Describe the difference between a physical change and a chemical change in one sentence.
Chemical change produces one or more new substances with different properties; physical change alters form or appearance but not composition.
List three signs that a chemical change has taken place
Color change, gas production (bubbles/fizz), temperature change, formation of a precipitate, light or sound produced.
The process of liquid to gas is called......
Evaporation
Fill in the blanks: Endothermic reactions _____________ energy, so the temperature of the surroundings ______________. (Use word bank: increases, decreases, absorb, release)
Endothermic reactions absorb energy, so the temperature of the surroundings decreases
Give two examples from everyday life of a physical change and explain why each is physical.
Examples: Melting ice (physical — same substance H2O), tearing paper (physical — still paper).
List two indicators that a physical change has occurred.
"NO new substance created" and "Bonds don’t change" indicate physical change.
The process of solid to liquid is called ........
Melting (also called fusion)
Fill in the blanks: Exothermic reactions ______________ energy, so the temperature of the surroundings ______________. (Use word bank: increases, decreases, absorb, release)
Exothermic reactions release energy, so the temperature of the surroundings increases.
The study guide says "During a chemical change, chemical bonds are broken and new bonds form." Explain what this means using the example of burning paper.
Burning paper: bonds in cellulose break and new compounds (ash, gases) form — new substances result.
Explain why burning paper is a "chemical change" and shredding paper isa "physical change"
Burning paper: new substances (ash, smoke) → chemical. Shredding: same substance, different shape → physical.
The process of gas to solid is called .......
Deposition (or condensation? careful: gas to solid = deposition)
Label each simple example as Exothermic (EXO) or Endothermic (ENDO): Melting ice; Burning wood.
Melting ice — ENDO; Burning wood — EXO
True or False: "During a chemical change, the number of molecules always remains the same." If false, correct the underlined term to make it true.
False. Replace "molecules" with "atoms" or note that atoms are rearranged; the number of atoms is conserved but molecules may change.
Look at the image of solid ice turning into liquid water. Is this image showing a chemical or physical change? How do you know?
Evidence: new substances labeled, bubbles of a different gas forming that weren’t present before, color change not due to phase change
Define "sublimation"
Sublimation: solid to gas without passing through liquid (example: dry ice turning into CO2 gas).
Explain why an instant ice pack feels cold when activated (is it endothermic or exothermic?) and name which process (absorb/release) happens.
Instant ice pack: usually endothermic — it absorbs heat from surroundings, so it feels cold
Read this statement and rewrite it correctly if needed: "A tree bent by a strong wind & a window shattering are examples of chemical changes." Explain your correction.
False — both are physical changes (bending and shattering change form but do not create new substances).
The study guide lists "Difficult to reverse" and "Can often be reversed" as features. Give one real example of each and explain why one is harder to reverse than the other.
Can often be reversed: freezing/melting water (reversible). Difficult to reverse: burning wood (ash and gases formed, can’t easily reconstruct original wood).
From the word bank (sublimation, condensation, evaporation, melting, deposition, solidification), place each word next to the correct description:
a) Gas becomes liquid
b) Liquid becomes solid
c) Solid becomes gas without becoming liquid
d) Liquid becomes gas
e) Solid becomes liquid
f) Gas becomes solid (synonym)
a) Condensation; b) Solidification (or freezing); c) Sublimation; d) Evaporation; e) Melting; f) Deposition
"When CO2 dissolves in water, carbonic acid is produced. The carbonic acid in a fizzy drink can also turn back into water and CO2 when it's no longer under pressure." Explain whether creating carbonic acid was a chemical or physical change and justify your answer in 2–3 sentences.
When CO2 dissolves in water to form carbonic acid, that is a chemical change because new substance (carbonic acid) form; when pressure is released and it turns back to CO2 and water, that decomposition is also a chemical change (reversible chemical reaction).