Chemical Changes and State

Chemical Changes and Physical Properties

• A chemical change represents a change in the substance itself, such as a log burning.
• An example of a chemical change that produces a new substance is combining ingredients and baking a cake.
• Water changing from a solid to a liquid is an example of a change of state.

Phases of Matter

• In a gas, particles of matter have the greatest freedom of movement.
• In a gas, particles move about most easily.
• A substance heated to its melting point will change from a solid to a liquid.

Physical Changes

• The breaking of a window involves a physical change only because no new substances are created.
• An example of a physical change is an ice cube changing from a solid to a liquid.

Measurement and Instruments

• A balance is used to measure the mass of an object.
• The abbreviation for centimeter is cm.

Chemical Properties

• If you describe methane as a gas that easily catches fire, you are describing a chemical property.
• When an acid reacts with zinc, it produces a gas, which is an example of a chemical change.

Chemistry and Energy

• The study of matter and how it changes is called chemistry.
• Chemical change means a chemical reaction.
• Energy is the ability to do work.
• As pressure on a gas increases, its volume decreases.
• As the temperature of a gas increases, its volume increases.
• Different kinds of energy are involved when we ride our bikes down a hill.

Properties of Matter

• A chemical change occurs when one or more substances combine or break apart to form a new substance.
• A pure substance is made up of only one kind of material and has definite properties.
• Hardness is a physical property.
• A corrosive substance eats away another material.
• The temperature at which a liquid boils is called its boiling point.
• The temperature at which a solid melts is called its melting point.