2. PRO Physical Changes: empirical premiseο
Why does ice melt when it is heated?
Premise (P): When a solid is heated, the particles gain kinetic energy.
Reasoning (R): As a result, the particles vibrate more strongly and eventually overcome the forces holding them in fixed positions.
Outcome (O): Therefore, the ice changes state into a liquid.
Why does a metal rod become longer when heated?
Premise (P): When a material is heated, its particles gain kinetic energy and move further apart.
Reasoning (R): As a result, the particles vibrate more and push against each other with greater force, increasing the spacing between them.
Outcome (O): Therefore, the metal rod expands and becomes longer.
Why does modelling clay change shape when it is pressed?
Premise (P): When modelling clay is pressed, its particles can slide past one another due to its soft, malleable structure.
Reasoning (R): As a result, the applied force rearranges the particles into new positions without disrupting the substanceβs composition.
Outcome (O): Therefore, the clay changes shape but remains the same substance.
Water boiling
Complete the Outcome (O).
Why does water turn into water vapour when it is boiled?
Premise (P): When water is boiled, the heat energy allows the liquid particles to move rapidly and break free from the forces holding them together.
Reasoning (R): As a result, the particles move farther apart and escape from the surface of the liquid.
Outcome (O): __________________, the liquid changes __________________ into a gas.
Reveal Answer Key
Premise (P): When water is boiled, the heat energy allows the liquid particles to move rapidly and break free from the forces holding them together.
Reasoning (R): As a result, the particles move farther apart and escape from the surface of the liquid.
Outcome (O): Therefore, the liquid changes state into a gas.
Stretching a rubber band
Complete the Reasoning (R).
Why does a rubber band stretch when pulled?
Premise (P): When a rubber band is pulled, its long, coiled polymer chains can uncoil.
Reasoning (R): __________________, the force straightens and extends these __________________ without breaking them.
Outcome (O): Therefore, the rubber band becomes longer but remains the same material.
Reveal Answer Key
Premise (P): When a rubber band is pulled, its long, coiled polymer chains can uncoil.
Reasoning (R): As a result, the force straightens and extends these chains without breaking them.
Outcome (O): Therefore, the rubber band becomes longer but remains the same material.
Snapping chalk
Complete the Premise (P).
Why does a piece of chalk break when you bend it?
Premise (P): _______________ a bending force is applied to __________________, its rigid structure does not allow the __________________ to move.
Reasoning (R): As a result, the particles separate instead of shifting.
Outcome (O): Therefore, the chalk breaks into smaller pieces without changing its substance.
Reveal Answer Key
Premise (P): When a bending force is applied to chalk, its rigid structure does not allow the particles to move.
Reasoning (R): As a result, the particles separate instead of shifting.
Outcome (O): Therefore, the chalk breaks into smaller pieces without changing its substance.
Fill in the Gaps β Fixed shape
Complete the Explanation by filling in the missing words (processes).
Word list (A β Z): deform, flow, move, spread
Why does a solid keep its shape?
Premise (P): When a material is a solid, its particles are tightly packed and held in fixed positions.
Reasoning (R): As a result, the particles cannot __________________ freely, so the solid cannot __________________ or spread out like a liquid or gas.
Outcome (O): Therefore, a solid keeps its shape unless a force strong enough to __________________ it is applied.
Reveal Answer Key
Premise (P): When a material is a solid, its particles are tightly packed and held in fixed positions.
Reasoning (R): As a result, the particles cannot move freely, so the solid cannot flow or spread out like a liquid or gas.
Outcome (O): Therefore, a solid keeps its shape unless a force strong enough to deform it is applied.
Fill in the Gaps β Melting butter
Complete the Explanation by filling in the missing nouns.
Word list (A β Z): energy β’ liquid β’ particles β’ positions β’ solid β’ state
Why does butter melt when it is heated?
Premise (P): When a solid is heated, its __________________ gain kinetic __________________.
Reasoning (R): As a result, the particles vibrate more strongly and begin to loosen from their fixed __________________.
Outcome (O): Therefore, the __________________ changes __________________ into a __________________.
Reveal Answer Key
Premise (P): When a solid is heated, its particles gain kinetic energy.
Reasoning (R): As a result, the particles vibrate more strongly and begin to loosen from their fixed positions.
Outcome (O): Therefore, the solid changes state into a liquid.
Fill in the Gaps β Squashing a sponge
Complete the Explanation by filling in the missing adjectives or adverbs (modifiers).
Word list (A β Z): flexible β’ high β’ rigid β’ soft β’ strong β’ tightly
Why does a sponge compress when you squeeze it?
Premise (P): When a sponge is pressed, its particles, which are not __________________ packed, can move easily.
Reasoning (R): As a result, the particles shift, and the sponge bends because it is __________________.
Outcome (O): Therefore, the sponge becomes smaller under __________________ pressure.
Reveal Answer Key
Premise (P): When a sponge is pressed, its particles, which are not tightly packed, can move easily.
Reasoning (R): As a result, the particles shift, and the sponge bends because it is flexible.
Outcome (O): Therefore, the sponge becomes smaller under high pressure.
Fill in the Gaps β Wet mirror
Complete the Explanation by filling in the missing text connectives.
Word list (A β Z): As a result β’ Therefore β’ When
Why does water form on a bathroom mirror?
Premise (P): __________________ water vapour in the air touches a cooler surface, it loses energy.
Reasoning (R): __________________, the particles slow down and change state from gas to liquid.
Outcome (O): __________________, tiny droplets form on the mirror.
Reveal Answer Key
Premise (P): When water vapour in the air touches a cooler surface, it loses energy.
Reasoning (R): As a result, the particles slow down and change state from gas to liquid.
Outcome (O): Therefore, tiny droplets form on the mirror.
Fill in the Gaps β Overnight frost
Complete the Explanation by filling in the missing text connectives.
Word list (A β Z): As a result β’ Therefore β’ When
Why does frost form on grass overnight?
Premise (P): __________________ the air temperature drops below freezing, water vapour in the air is ready to change state.
Reasoning (R): __________________, the particles lose energy and change directly into ice crystals.
Outcome (O): __________________, frost forms on the grass.
Reveal Answer Key
Premise (P): When the air temperature drops below freezing, water vapour in the air is ready to change state.
Reasoning (R): As a result, the particles lose energy and change directly into ice crystals.
Outcome (O): Therefore, frost forms on the grass.
Fill in the Gaps β Cold to touch
Complete the Explanation by filling in the missing verbs (material processes).
Word list (A β Z): conducts β’ feels β’ loses β’ move β’ transfers
Why does a metal spoon feel cold in winter?
Premise (P): When you touch a metal spoon, it __________________ heat quickly, allowing energy to __________________ from your hand into the spoon.
Reasoning (R): As a result, your hand __________________ warmth as heat __________________ away into the metal.
Outcome (O): Therefore, the spoon __________________ cold to touch.
Reveal Answer Key
Premise (P): When you touch a metal spoon, it conducts heat quickly, allowing energy to move from your hand into the spoon.
Reasoning (R): As a result, your hand loses warmth as heat transfers away into the metal.
Outcome (O): Therefore, the spoon feels cold to touch.
Fill in the Gaps β Clothing in wind
Complete the Explanation by filling in the missing describers (adjectives/adverbs).
Word list (A β Z): faster β’ moving β’ moist β’ more
Why does wet clothing dry on a windy day?
Premise (P): When water is exposed to __________________ air, the water vapour is carried away from the surface.
Reasoning (R): As a result, __________________ liquid water can evaporate because the __________________ air above is removed.
Outcome (O): Therefore, the clothing dries __________________.
Reveal Answer Key
Premise (P): When water is exposed to moving air, the water vapour is carried away from the surface.
Reasoning (R): As a result, more liquid water can evaporate because the moist air above is removed.
Outcome (O): Therefore, the clothing dries faster.
Fill in the Gaps β Disappearing puddle
Complete the Explanation by filling in the missing verbs (material processes).
Word list (A β Z): absorbs β’ changes β’ evaporate β’ gain β’ rise
Why does a puddle disappear on a sunny day?
Premise (P): When a puddle __________________ heat energy from the Sun, its water particles __________________ energy.
Reasoning (R): As a result, the particles move faster, break free from the liquid, and __________________ into water vapour.
Outcome (O): Therefore, the puddle disappears as the liquid __________________ into a gas.
Reveal Answer Key
Premise (P): When a puddle absorbs heat energy from the Sun, its water particles gain energy.
Reasoning (R): As a result, the particles move faster, break free from the liquid, and evaporate into water vapour.
Outcome (O): Therefore, the puddle disappears as the liquid changes into a gas.
Shrinking a balloon
Explain the following phenomenon using the PRO structure.
Why does a balloon shrink when placed in the freezer?
Reveal Answer Key
Premise (P): When a balloon is placed in a freezer, the air particles inside lose energy due to the cold temperature.
Reasoning (R): As a result, the particles move more slowly and take up less space.
Outcome (O): Therefore, the balloon becomes smaller in the freezer.
Sun dried towel
Explain the following phenomenon using the PRO structure.
Why does a wet towel dry when left in the sun?
Reveal Answer Key
Premise (P): When a wet towel is left in the Sun, the water particles gain energy from the heat.
Reasoning (R): As a result, the particles move faster and escape into the air as water vapour.
Outcome (O): Therefore, the towel becomes dry.