6.1 When Substances Change Flashcards Preview

Year 8 Science Exam Semester 2 > 6.1 When Substances Change > Flashcards

Flashcards in 6.1 When Substances Change Deck (30):
1

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

Chemical change

2

Is a physical change reversible?

Usually it is

3

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

The physical properties

4

What changes occur in physical changes?

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

5

How does an object change shape or form?

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

6

When does expansion and contraction occur?

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

7

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

More space

8

What happens to the volume when an object is expanded?

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

9

How does an object contract?

When it is cooled it contracts

10

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

The volume increases while the density decreases

11

What do thermometers use to show a temperature change?

The expansion and contraction of mercury and ethanol.

12

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

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

13

What change of state occurs in melting?

Solid to liquid

14

What change of state occurs in evaporation?

Liquid to gas

15

What change of state happens in condensation?

Gas to liquid

16

What change of state occurs in freezing/solidification?

Liquid to solid

17

What change of state occurs in sublimation?

Solid to gas

18

What change of state occurs in deposition?

Gas to solid

19

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

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.

20

How can we tell a permanent colour change has occurred?

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.

21

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

Bubbles, smell a new smell or see smoke

22

How is a precipitate formed?

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.

23

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

Exothermic

24

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

Endothermic

25

What energy does exothermic energy produce?

Heat, light and sound

26

What are some examples of exothermic energy?

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

27

What is an endothermic chemical change?

A chemical change that absorbs energy from its surroundings.

28

Is a physical change endothermic or exothermic?

It can be both

29

Why do you feel cooler when you sweat?

Because your sweat evaporates and absorbs heat from your skin.

30

Is condensation endothermic or exothermic?

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