UNIT: PHYSICAL SCIENCE
Chapter 9: Properties and Changes of Matter
PHYSICAL PROPERTIES OF
MATTER
WHAT IS MATTER?
• Matter- included solids, liquids, and gases.
• Examples: mountains, footballs, lakes, clouds, and air.
• Mass- amount of matter in an object.
• Measured in units of grams (g) or kilograms (kg).
• Weight- the amount of the pull of gravity between the object and Earth
• An object with a large mass normally has a large weight.
A balance is used to measure mass.
DENSITY
• Why does oil float on water?
• Density- the amount of mass in a given
space.
• You can find the density by
• Finding the mass
• Finding the volume
• Dividing the
mass𝑚𝑎𝑠𝑠
by the
volume
𝑔
(𝑔)
𝑑𝑒𝑛𝑠𝑖𝑡𝑦 𝑐𝑚3 = 𝑣𝑜𝑙𝑢𝑚𝑒 (𝑐𝑚3 )
• When an object is placed in a less dense
liquid or gas, the object will sink to the
bottom.
• When an object is placed in a more dense
liquid or gas, the object will float to the top.
• If the object has the same density as the
liquid or gas, it will “hover” in place.
WHAT ARE PHYSICAL PROPERTIES?
• Properties- things you can observe with
your senses.
• Odor, hardness, color, shine, mass,
density
• Physical Properties- can be observed
without changing the identity of the
substance.
• When you describe a rock, the rock is
not changing into something else- it
stays the same.
• Examples: density, the substance’s
ability to conduct electricity,
magnetism
• A substance’s state, whether it is a solid,
liquid, or gas, is another important
physical property.
WHAT IS A PHYSICAL CHANGE?
• When heat turns a solid into a liquid or a liquid into a gas, the identity of the
substance is unchanged.
• Physical Change- a change in size, shape, or state without forming a new
substance.
• Example- an ice cube melting to liquid water.
• Different substances are in different states at room temperature. These substances
also change state at different temperatures.
• Melting Point- temperature at which a substance changes from a solid to a liquid.
• Boiling Point- the temperature at which a substance changes from a liquid to a gas.
• Freezing Point- the temperature at which a substance changes from a liquid to a solid.
• All of these temperatures vary from substance to substance.
WHAT ARE MIXTURES?
• Mixture- any combination of two or
more substances keep their own
properties.
• Examples: tossed salad, chocolate
milk
• Even though the substances in a
mixture keep their own properties,
you may not always recognize
these properties
• Example: Milk is a mixture. If you
add vinegar to milk it will separate
the substances making up the milk.
TYPES OF MIXTURES
• Suspension- a mixture made of parts that separate upon standing.
• Example: Oil and water
• Can sometimes be separated using a strainer
• Emulsion- a suspension of two liquids that usually do not mix together.
• Example: the few seconds after you shake up oil and water
• Colloids- contains undissolved particles or droplets that stay mixed in another substance.
• Examples: Fog is a liquid-in-gas colloid, Smoke is a solid-in-gas colloid
• Solution- a mixture of one substance dissolved in another so that the properties are the
same throughout.
• Example: Kool Aid mixed in water.
• The Kool Aid particles are soluble- they can be dissolved in water. When it is poured into the water
it is a solute- substances that can be dissolved.
• The water is the solvent- part of the solution that dissolves the solvent.
• Alloy- solutions of one or more metals and other solids.
• 14-carat gold- an alloy of gold, copper, and silver
• Sterling silver – an alloy of silver and copper.
• Pennies are made of an alloy of copper and zinc
WHY DO THINGS FLOAT?
• Pressure- the weight or force on a given area.
• When an object is submerged in a fluid, the fluid “pushes” in on the object.
• The push is greater at the bottom than on the top, so the fluid pushes the object
toward the surface.
• This push is called buoyant force.
• The amount of buoyant force equals the weight of the water that is
displaced.
• Example: water rising when you get in a bathtub
• Buoyant force varies on the weight and density of the object.