Comparing Kinds of Matter Chapter 5

Lesson 3: Changes of State

Physical Change• Physical change: a change that occurs

that does not change the identity of the substance

• alters the form of an object without changing what type of matter it is

• the three states of matter solids, liquids, and gases are physical properties

•

Physical changes are those changes that do not result in the

production of a new substance.  If you melt a block of ice, you still

have H2O at the end of the

change.   

Examples of Physical Changes

• If you break a bottle, you still have glass.

• Painting your nails will not stop them from being fingernails. 

• Some common examples of physical changes are: melting, freezing, condensing, breaking, crushing, cutting, and bending.

Some, but not all physical changes can be reversed. You could

refreeze the water into ice, but you cannot put your hair back together

if you don’t like your haircut!

Special types of physical changes where any object changes state, such as when water freezes or

evaporates, are sometimes called change of state operations.

Changes in State

• If a solid gains enough heat it turns into a liquid. Example: ice to water

• Add more heat and the liquid changes into a gas. Example: water to steam

• When a solid changes into a gas and skips the liquid state it sublimates

example: dry ice to carbon dioxide gas

When does matter change state?• When a substance melts or boils, it absorbs heat

energy

• The temperature at which a substance changes from a solid to a liquid is its melting point.

• The temperature at which a substance changes from a liquid to a gas is its boiling point.

• The temperature at which a substance changes from a liquid to a solid is its freezing point.

What are expansion and contraction?

• An increase in an object’s volume when it is heated is called thermal expansion.

• A decrease in its volume when it is cooled is called thermal contraction

Lesson 4: Mixtures

• a physical combination of substances

• You can separate mixtures back into their original substances

• Example: Trail Mix

•

Types of Mixtures• Mixtures that have parts that you can clearly see are

called heterogeneous mixtures.

• Heterogeneous Mixtures that are smooth and creamy and separate and settle are called suspension mixtures. Example: Orange Juice

• Colloid is a mixture like a suspension, except that its parts do not settle. A mixture that looks cloudy or creamy.

• Examples: mayonnaise, smoke, and foam

•

Solutions

• A solution is a mixture with parts that blend so that it looks the same everywhere, even under a microscope.

• Solutions are homogeneous mixtures

• Example: Sugar and water

What are the parts of a solution?• Solute – part of the solution in the larger

amount that dissolves. The sugar in the sugar water

• Solvent – the other substance. The water.

• Solutions can be made with solids, liquids, and gases

• Alloy – a solution of a metal and another solid (often another metal)

Examples of Solutions

• window cleaner, bleach, vinegar, and beverages

• Some when mixed are dangerous.

•

Solution Limits

• Solidity – the maximum amount of a solute that can dissolve in a solvent

• Water is often called the universal solvent because it can dissolve many things

How can you take mixtures apart?

• To separate one part of a mixture from another, you can use a physical property

• Distillation is the process of separating liquids by using evaporation and condensation. When two liquids in a mixture have different boiling points, they can be separated by distillation

• Chromatography – in this process a liquid travels up small paper and carries small substances. The substances in the liquid travel at different speeds

How are mixtures used?

• Colloids - cheese, low-fat milk, whipped cream, gelatin, marshmallows, and paint

• Copper is alloyed with zinc to make brass