Particles And Reactions

Question 1

What is a solid?

Answer 1

A solid can not:

• be squashed or compressed
• change shape
• change volume
• flow

The bonds between atoms are very strong, though atoms still vibrate a little.

Question 2

What is a liquid?

Answer 2

A liquid can not:

• be squashed or compressed
• change volume

A liquid can:

• change shape
• flow

The bonds between atoms are weaker in a liquid, and are moving around each other.

Question 3

What is a gas?

Answer 3

A gas can:

• be squashed or compressed
• change shape
• change volume
• flow

There are no bonds between atoms in a gas, so they bounce around freely, colliding with other gas particles, as well as particles of solids and liquids.

Question 4

How do you get between a solid and a liquid?

Answer 4

Solid —> liquid is melting, and more heat is applied.

Liquid —> solid is freezing, and less heat is applied.

Question 5

How do you get between a liquid and a gas?

Answer 5

Liquid —> gas is evaporation or boiling, and more heat is applied (evaporation is just the surface area evaporating, boiling is so hot that the whole thing is trying to evaporate at once).

Gas —> liquid is condensing, and less heat is applied.

Question 6

How do you get between a solid and a gas?

Answer 6

Solid —> gas is sublimation, and more heat is applied.

Gas —> solid is deposition, and less heat is applied.

Question 7

What is a physical/reversible change?

Answer 7

• No new substances are formed

- easy to reverse

Question 8

What is a chemical/irreversible change?

Answer 8

• There may be a colour change
• energy/heat may be taken in (endothermic)
• energy/heat may be produced (exothermic)
• a gas may be produced
• there may be a change in mass
• difficult/impossible to reverse

Question 9

What is diffusion?

Answer 9

Diffusion is the spreading out of one substance through another, without external mixing. Only a liquid or gas can be involved with diffusion.

Question 10

What is diffusion and particle theory?

Answer 10

In gases, there is lots of space between particles, and particles are moving slowly. In liquids, there is not much space between particles, and they are moving slower. Therefore, diffusion is quicker in gases than in liquids.

Question 11

What is the test and result for Hydrogen?

Answer 11

Hydrochloric acid and magnesium ribbon are put in a test tube. When a lit splint is introduced, the result should be a squeaky pop.

Question 12

What is the test and result for Carbon Dioxide?

Answer 12

Limewater is put into Carbon Dioxide. The result should be milky white limewater.

Question 13

What is the test and result for Oxygen?

Answer 13

A glowing splint is introduced to a tube of Oxygen. The result should be that the splint delights.

Question 14

What is effervescence?

Answer 14

An effervescent reaction produces gas i.e. it is fizzy.

Question 15

How do we know that burning is a chemical reaction?

Answer 15

Burning gives three signs of a chemical reaction:

• exothermic
• gives out light energy
• makes sound energy

Question 16

How do we stay safe around combustion/fire?

Answer 16

• Stay well away
• do not touch it
• extinguish it afterwards, and throw it away
• keep it away from other flammable substances
• adult supervision at all times
• do not breathe in the smoke
• be alert and ready for anything
• have available fire escape routes
• have working fire alarms
• do not play or mess around with it

Question 17

What is always the product of combustion?

Answer 17

After combustion, the remaining substance is called an oxide (e.g. Carbon Dioxide).

Question 18

What is required to achieve complete combustion?

Answer 18

To achieve complete combustion, there must be plenty of oxygen.

Question 19

What is required to achieve combustion?

Answer 19

To achieve combustion, there must be fuel, heat and Oxygen.