Physical Properties & Changes

Physical Changes
Notes

Physical and chemical
properties can be used to
identify substances.

PHYSICAL PROPERTIES
can be observed and
measured without
changing the kind of
matter being studied.

Multiple Choice

When you observe a physical property, the substance __________.

• changes

• does not change

• burns

• melts

Examples of Physical Properties

● Shape
● Density
● Solubility
● Odor
● Melting point
● Boiling point
● Color

Multiple Choice

An example of a physical property is __________.

• flammability

• ability to rust

• acidity

• color

Multiple Choice

Matter has two basic properties: physical properties and chemical properties. Which of these statements best describes physical properties?

• Physical properties can be observed without changing the identity of a substance.

• Physical properties behave identically for all matter under the same conditions.

• Physical properties cause atoms and molecules to change structure when substances are mixed.

• Physical properties are observed by seeing how a substance reacts with other substances.

Melting Point

●The temperature at which a
solid can change to a liquid.

●The temperature at which a
pure substance melts is
unchanging under constant
conditions.

●Therefore, the melting point
of a pure substance can be
used as a physical property
for identification. Ice melts to
form liquid water at 00C
(32oF).

Boiling Point

●The temperature at which a liquid boils.

●During the process of boiling a substance changes from
a liquid to a gas.

●Boiling begins when the liquid starts to form bubbles
throughout, which grow larger, rise to the surface, and
burst.

●As long as the substance is boiling the temperature of
the liquid remains constant (at the boiling point).

●Boiling point is unchanging under constant conditions for
a given substance and therefore can be used as a
physical property for identification of the substance.

●The boiling point for pure water at sea level is 100oC or
212oF.

Multiple Choice

Sal is given a sample of an unknown liquid to test in the laboratory. Sal thinks the liquid might be water. Which of these physical properties would be most helpful for Sal to determine the identity of the liquid?

• mass

• boiling point

• color

• volume

Density

●Density is a property that describes the
relationship between the mass of a material
and its volume.

●Substances that have higher densities
contain more matter in a given volume.

●The density of a substance will stay the
same no matter how large or small the
sample of the substance, and therefore,
density can be used as a physical property
for identification of the substance.

●For example, the density of lead is much
greater than the density of aluminum.

Multiple Choice

Two liquid substances are placed in a container. One liquid sinks to the bottom and the other liquids floats on top. Which liquid has the greater density of the 2 liquids?

• The liquid that floats has the greatest density.

• Both liquids have the same density.

• Both liquids cancel out the density of each other.

• The liquid that sinks has the greatest density.

Color

●Color can be used to help
identify a substance, along
with other properties.

●By itself color is not a
significant identifier of a
substance.

●Absence of color is also a
physical property.

Multiple Choice

All matter has both physical and chemical properties. A physical property is one that does not change the chemical nature of matter. Which of these choices is a physical property?

• solubility

• flammability

• ability to rust

• reaction with water

Physical changes occur
when there is any change
in a physical property of
a substance.

PHYSICAL CHANGES
do not change the
composition of a
substance, only the
physical properties.

Evidence of physical

changes include:

Change in state of matter

&

Change in size or shape

Change in state of matter

●When a substance changes from one state of matter to another
(for example, changing from solid to liquid, from liquid to solid, or
from liquid to gas), the composition of the substance remains the
same.

●Examples of change in state might include: melting of ice cream,
hardening of melted wax, or evaporation of water from wet
clothes.

●When a substance changes directly from a gas to a solid (the
forming of frost from water vapor) or from a solid to a gas (dry ice,
solid air fresheners) that change of state is called sublimation.
This is still a physical change because the composition of the
substance remains the same.

As molecules are heated they being to move faster and more erratic.

As molecules cool (lose heat) they begin to slow down and move closer to each other.​

How do the molecules move???

Multiple Choice

An ice cube is put into a heated pan. What will most likely happen to the molecules in the ice as the ice is heated?

• The molecules will begin to move slower.

• The molecules will begin to move faster.

• The molecules will begin to increase in density.

• The molecules will begin to condense in the air.

Multiple Choice

What happens to water molecules during the boiling process?

• They move faster and move farther apart as they absorb heat.

• They move more slowly but move farther apart as they lose heat.

• They move faster and remain close together as they absorb heat.

• They move faster and move farther apart as they lose heat.

Change in size or shape

●When a substance changes in size or shape (for example, cutting,
tearing, dissolving, stretching, or wrinkling), its composition
remains the same.

●Examples of change in size or shape might include: shredding
paper, dissolving sugar in water, stretching a rubber band,
wadding up a piece of paper, or denting a piece of metal.

Multiple Choice

Which of the following is a physical change?

• baking a cake

• burning wood

• frying an egg

• mixing cookie dough

Multiple Choice

Which of the following is NOT a physical change?

• dying your hair

• cracking an egg

• nailing together boards of wood

• baking a cake

Multiple Choice

When sandpaper smooths a piece of wood, this is an example of a __________.

• chemical change

• physical change

• both physical and chemical change

• neither chemical nor physical change