6.1 When Substances Change

Question 1

In what type of change does a new substance form in?

Answer 1

Chemical change

Question 2

Is a physical change reversible?

Answer 2

Usually it is

Question 3

What may change in a physical change even though no new substance is formed?

Answer 3

The physical properties

Question 4

What changes occur in physical changes?

Answer 4

Shape or form, expansion and contraction, change of state or mixing substances together.

Question 5

How does an object change shape or form?

Answer 5

When force is applied, breaking, bending, stretching, crushing, twisting or compressing the object

Question 6

When does expansion and contraction occur?

Answer 6

They occur when the temperature of the substance increases or decreases.

Question 7

Does an object take up more or less space when heated?

Answer 7

More space

Question 8

What happens to the volume when an object is expanded?

Answer 8

The volume increases, density decreases and no new substance is formed.

Question 9

How does an object contract?

Answer 9

When it is cooled it contracts

Question 10

What happens to the volume and density when an object is cooled?

Answer 10

The volume increases while the density decreases

Question 11

What do thermometers use to show a temperature change?

Answer 11

The expansion and contraction of mercury and ethanol.

Question 12

What happens to the state of an object if enough heat is applied to it?

Answer 12

It expands and changes state and the other way round if an object is cooled enough it contracts and changes state.

Question 13

What change of state occurs in melting?

Answer 13

Solid to liquid

Question 14

What change of state occurs in evaporation?

Answer 14

Liquid to gas

Question 15

What change of state happens in condensation?

Answer 15

Gas to liquid

Question 16

What change of state occurs in freezing/solidification?

Answer 16

Liquid to solid

Question 17

What change of state occurs in sublimation?

Answer 17

Solid to gas

Question 18

What change of state occurs in deposition?

Answer 18

Gas to solid

Question 19

What are some things that show you a chemical change has occurred?

Answer 19

Seeing a colour change,
Smelling a gas or seeing bubbles,
Seeing a new solid forming a clear solution (precipitate),
Observing an energy change, produced or absorbed.

Question 20

How can we tell a permanent colour change has occurred?

Answer 20

See a new substance has formed,
Has a new colour than the one it started with,
If you burn a match, the piece of paper or piece of toast, it produces carbon,
A physical change can also cause a colour change.

Question 21

What is a way that gas can be observed in a chemical change?

Answer 21

Bubbles, smell a new smell or see smoke

Question 22

How is a precipitate formed?

Answer 22

When two solutions are mixed, they occasionally form a solid. The solid falls out of the solution and sinks to the bottom, it occurs in pipes and drains. It is also formed when a gas is bubbled through a liquid.

Question 23

When a chemical change occurs and energy is produced, what is the energy called?

Answer 23

Exothermic

Question 24

When a chemical change occurs and energy is absorbed, what do we call that energy?

Answer 24

Endothermic

Question 25

What energy does exothermic energy produce?

Answer 25

Heat, light and sound

Question 26

What are some examples of exothermic energy?

Answer 26

Fireworks, firing a bullet, sparklers, when your body turns food into energy

Question 27

What is an endothermic chemical change?

Answer 27

A chemical change that absorbs energy from its surroundings.

Question 28

Is a physical change endothermic or exothermic?

Answer 28

It can be both

Question 29

Why do you feel cooler when you sweat?

Answer 29

Because your sweat evaporates and absorbs heat from your skin.

Question 30

Is condensation endothermic or exothermic?

Answer 30

Exothermic because it can condense on your skin releasing hot energy.