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physical and chemical change (identifying physical change (changes of…
physical and chemical change
identifying physical change
key feature is that no new substance is produced during the change.
changing shape or form
these do not produce new substances.
expantion and contraction
they also occur when the temperature of a substance increases or decreases. expansion occurs, the volume of the new object increases and its density decreases, but no new substance is formed. contraction is when a solid, liquid, or gas is cooled and it contracts-the volume of the substance decreases annd the density increases.
changes of state
if enough heat is applied to a substance, then it will change state with liquids, solids, and gases
melting
when a solid is heated enough, it will melt to form a liquid.
freezing
when a liquid is cooled enough, it will form a solid.
evaporation
evaporation occurs whe a liquid is warmed and becomes a gas
condensation
the opposite of evaporation. its when a gas cools and becomes a liquid.
mixing
dissolving
when a solid is dissolved in a liquid, they form a mixture.
identifying chemical change
a new substance is formed in a chemical change
you can detect the presence of a new substance by:
seeing a change in colour
smelling a gas or seeing bubbles
seeing light or feeling a change in temperature
seeing a new solid forming in a clear solution (called a precipitate)