UNIT: PHYSICAL SCIENCEChapter 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 mass by the volume

• 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.