Worksheet: Physical and Chemical Changes

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Go to the answers for the first seven examples


Example #1: Label each process as a physical or chemical change:

(a) perfume evaporating on your skin
(b) butter melting
(c) wood rotting
(d) charcoal heating a grill
(e) autumn leaves changing color
(f) a hot glass cracking when placed in cold water
(g) melting copper metal
(h) burning sugar
(i) mixing sugar in water
(j) digesting food

Example #2: Which of the following would NOT be a physical change?

(a) freezing water to make ice cubes
(b) melting gold to make jewelry
(c) burning gasoline in a lawnmower
(d) boiling water for soup
(e) tearing a piece of aluminum foil

Example #3: Which of the following is NOT a physical change?

(a) grating cheese
(b) melting cheese
(c) fermenting of cheese
(d) mixing two cheeses in a bowl

Example #4: Which are physical and which are chemical changes?

(a) boil
(b) burn (combustion)
(c) condense
(d) corrode
(e) crumple
(f) ferment
(g) melt
(h) rust
(i) crush
(j) freeze
(k) oxidize
(l) tarnish
(m) explode
(n) grind
(o) rot
(p) vaporize
(q) photosynthesis
(r) sublimation

Example #5: Label each process as a physical or chemical change:

(a) Moth balls gradually vaporize in a closet
(b) hydrofluoric acid attacks glass (used to etch glassware)
(c) A chef making a sauce with brandy is able to burn off the alcohol from the brandy, leaving just the brandy flavoring
(d) Chlorine gas liquefies at −35 °C under normal pressure
(e) hydrogen burns in chlorine gas

Example #6: Label each process as a physical or chemical change:

(a) fogging a mirror with your breath
(b) breaking a bone
(c) mending a broken bone
(d) burning paper
(e) slicing potatoes for fries
(f) mixing sugar with coffee
(g) frying chicken
(h) a nail rusting
(i) paper ripping
(j) wood burning
(k) mixing water and food coloring
(l) food molding (rotting)
(m) writing on paper
(n) dyeing fabric

Example #7: Which of the following statements describe chemical properties? Select all that apply

(a) Iron has a tendency to rust
(b) Rainwater in industrialized regions tends to be acidic
(c) Hemoglobin molecules have a red color
(d) When a glass of water is left out in the sun, the water gradually disappears
(e) Carbon dioxide in air is converted to more complex molecules by plants during photosynthesis
(f) An alloy of gold melts at a lower temperature than pure gold

Go to the answers for the first seven examples


Example #8: How is burning a candle both a physical and chemical change?

Solution:

physical change ---> the wax of the candle melts
chemical change ---> the liquid wax burns, producing CO2 and H2O. A bit of the wick also burns.

By the way, candles are usually made of paraffin wax, which is a mixture of several different solid hydrocarbons. An example of one would be C31O64.


Example #9: Wood undergoes a chemical reacion when it . . .

(a) is split    (b) is painted    (c) is cut    (d) decays

Solution:

Choice (d) is the correct choice. Various species of fungus digest the cellulose that makes up wood, converting it into carbon dioxide and water.

Example #10: Which of the following causes a chemical change?

(a) sugar added to soda
(b) Detergent added to water
(c) lemon juice added to milk
(d) Salt added to water

Solution:

Choice (c) is the correct choice. More specifically, the citric acid denatures the protein in the milk. denaturation involves the breaking and forming of chemical bonds, which is the definition of a chemical change.

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