Physical and Chemical Changes Review

Physical and Chemical Changes Review

By Denice Manning

During a physical change, substances are NOT altered chemically.

​They change from one state of matter to another.

Or, they separate or combine without breaking or making bonds. ​

Mixtures can be separated based on the physical properties of their components.

Making and separating mixtures are examples of a physical change.

What is a physical change?

The substance can change between the states of matter. For example, changing from a liquid to a solid or gas.

Change in state of matter

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The size the substance is altered to make it bigger or smaller. The shape can also be altered. For example, cutting wood, ripping paper, squeezing a sponge.

Change in size or shape

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Any change made can be easily undone allowing the substance to return to its original form. For example, an ice cube that melts can be refrozen.

Change is reversible

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During a chemical change, a substance combines in a chemical reaction to form one or more new substances with different chemical and physical properties.

A chemical reaction is a process by which the atoms of one or more substances are rearranged to form different substances​

The rate of the chemical reaction ​is affected by temperature, pressure, the concentration of the reactants, and the state of matter.

What is a chemical change?

​Reactions may either produce or absorb heat.

If heat is absorbed this is an endothermic reaction.

If heat is released this is an exothermic reaction. ​

Change in energy

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​A reaction may produce a solid substance called a precipitate or release gas.

If gas is produced it can be seen as bubbles or effervescence (fizzing).​

Production of a new substance

​During a reaction, light is sometimes produced.

It can be released in a flash or slowly. For example the chemicals in a glow stick. ​

Production of light

Multiple Choice

Which is an example of a chemical change?

• A chemical from skunks is added to odorless natural gas so that people can smell gas leaks.

• If a scuba diver surfaces too quickly, the change in pressure causes dissolved nitrogen to form bubbles in the blood.

• Over time, sand carried by the wind can grind rocks into natural arches and towers.

• Bending a glow stick breaks a divider so that two chemicals can mix and produce light.

Multiple Choice

Which is an example of a chemical change?

• When water is boiled, bubbles of gas appear, rise to the surface, and escape

• A small amount of red paint is mixed with yellow paint, creating orange paint

• When hydrogen peroxide is put on a cut, oxygen bubbles away, leaving water behind

• As water freezes, its molecules slow down and form ice crystals

Multiple Choice

Which action causes a chemical change?

• boiling water

• crushing sugar cubes

• sifting flour

• cooking eggs

Multiple Choice

Texture, color, states of matter, flexibility, freezing & melting points

• Chemical Property

• Physical Property

• Chemical Change

• Physical Change

Multiple Choice

Which of the following is an example of a chemical property?

• Melting

• Bending a paper clip

• Rusting

• Boiling water

Multiple Choice

A physical change is .....

• A change that doesn't change the identity of the substance

• a change that makes something new

• A chemical reaction

• A change that is irreversible

Multiple Choice

What is a precipitate?

• An insoluble reactant formed during a chemical reaction

• An insoluble product formed during a chemical reaction

• A soluble solvent in a saturated solution

• A soluble solute in a saturated solution

Multiple Choice

A measure of how much mass is in a volume of matter

• matter

• density

• weight

• compund

Multiple Choice

What is an example of a physical change?

• combustion

• corrosion

• recycling

• reactivity

Multiple Choice

Changing the size and shapes of pieces of wood would be a chemical change

• True

• False

Multiple Choice

In a physical change, the makeup o matter is changed.

• True

• False

Multiple Choice

Breaking up concrete is a physical change

• True

• False

Multiple Choice

Combining hydrogen and oxygen to make water is a physical change.

• True

• False

Multiple Choice

Which best describes a chemical change?

• A chemical change requires no change in energy

• A chemical change is easily reversed

• In a chemical change, there is only a change in the state

• In a chemical change, a new substance with different properties forms

Fill in the Blank

Chewing food to break it down into smaller particles represents a ______________ change.

Fill in the Blank

The changing of starch into sugars by enzymes in the digestive system represents a ___________ change.

Multiple Choice

Which best explains why blow drying your hair is a physical change?

• No change in substance

• No unexpected color change

• No gas was given off

• All of the above

Multiple Choice

Which best explains why leaving a piece of bread too long in a toaster leaving it black and the kitchen in smoke is a chemical change?

• A new substance is formed

• The change is reversible

• No change occurs

• The size changes

Multiple Choice

This best explains why a chemical change is observed when silver spoons are very dull and have black spots.

• A change of state occurs

• Silver oxide is produced

• This is a reversible change

• Energy is absorbed

Multiple Choice

This best describes why a straight piece of wire is coiled to form a spring is a physical change.

• No energy change occurs

• A new substance is formed

• The change is irreversible

• An unexpected color change occurs