A2 Changes in Mattere

What causes matter to change?

Its response to changes in energy.

How can energy affect matter?

Energy can make matter move or change entirely.

How can energy be changed in relation to matter?

Energy can be added to or taken away from matter.

What is a change of state?

A change that alters the appearance of matter but not its composition.

What happens to water when ice melts and is heated further?

Ice melts into liquid water, and with continued heating the water evaporates.

What is the formula of water in all three states?

H2O.

What is a physical change?

A change, such as a change of state, that does not alter the composition of matter.

What is a chemical change?

A change that alters the composition of matter.

What are examples of chemical changes from the slides?

Iron rusting, decomposition of water, wood burning, baking bread, cooking an egg, and lighting a match.

What does the Law of Conservation of Mass state?

In any chemical reaction, the mass of the products is equal to the mass of the reactants.

Can matter be created or destroyed in a chemical reaction?

No. Matter cannot be created or destroyed.

What happens to energy in chemical reactions?

All chemical reactions involve the release or absorption of energy.

What forms can released energy take?

Light, electricity, or sound.

How can physical properties be determined?

They can be determined without altering the identity of the sample.

What do chemical properties involve?

A chemical change.

What happens when a substance breaks down or reacts with another substance?

A new substance is produced, so the original sample is no longer present in its original form.

What observations suggest that a chemical change has probably occurred?

Two or more signs such as heat produced or absorbed, starting material used up, a new colour appearing, a starting colour disappearing, a material with new properties forming, gas bubbles forming in a liquid, or solid precipitate grains forming in a liquid.

What does exothermic mean in the slides?

Heat is produced.

What does endothermic mean in the slides?

Heat is absorbed.

What is a precipitate?

An insoluble solid formed in a chemical reaction between aqueous solutions.

What does aqueous mean?

A term for solutions in which water is the solvent.

What are examples of reactions that indicate a chemical property?

Reacting with water, air, pure oxygen, acids, or pure substances.

What other chemical properties are listed in the slides?

Toxicity, stability, and combustibility.

What is the difference between a physical and chemical change?

A physical change does not alter the composition of matter; a chemical change alters its composition and produces a new substance.

Is melting ice a physical or chemical change?

A physical change.

Is rusting iron a physical or chemical change?

A chemical change.

Is cutting an apple a physical or chemical change?

A physical change.

Is cooking an egg a physical or chemical change?

A chemical change.

Is dissolving sugar in water a physical or chemical change according to the practice answers?

A physical change.

Is a marshmallow being toasted a physical or chemical change according to the practice answers?

A chemical change.