Physical and Chemical Change

Question 1

Define physical change

Answer 1

Physical change is a change in which no new substance is formed.

Question 2

What are two examples of physical changes of shape

Answer 2

• Cutting Paper: The shape changes but the composition stays the same.
• Molding Clay: Changes its shape without affecting its chemical properties.

Question 3

What are two examples of expansion and contraction

Answer 3

• Heating Metal: When metal is heated it expands.
• Cooling Air: When air cools down it contracts.

Question 4

What are two examples of physical changes of state

Answer 4

• Melting Ice: When ice is heated it melts, changing its state from a solid to a liquid.
• Boiling Water: When water is boiled it evaporates, changing its state from a liquid to a gas.

Question 5

What are two examples of physical mixing

Answer 5

• Dissolving Salt in Water: When salt is dissolved into water it mixes into the water without changing the water’s chemical structure.
• Mixing Sand and Sugar: When sand and sugar are mixed, they combine physically but not chemically.

Question 6

What’s melting?

Answer 6

solid to liquid

Question 7

What’s freezing?

Answer 7

liquid to solid

Question 8

What’s evaporation?

Answer 8

liquid to gas

Question 9

What’s condensation?

Answer 9

gas to liquid

Question 10

Describe some examples of colour change that indicate chemical
change.

Answer 10

• Ripening of Bananas
• Brown Sugar
• Cooking Meat
• Bleaching Stains

Question 11

Describe the structure of solids

Answer 11

In solids, particles are closely packed together in a fixed, orderly arrangement

Question 12

Describe the structure of liquids

Answer 12

In liquids, particles are still close together but are not arranged in a fixed pattern. They are more loosely packed than in solids.

Question 13

Describe the structure of gases

Answer 13

In gases, particles are far apart and move independently of one another. There is no fixed arrangement.

Question 14

Describe particle behaviour when substances expand

Answer 14

When particles are heated up, they gain kinetic energy. This energy makes them move faster, causing them to move further apart. This causes the solid/liquid to expand (grow in size).

Question 15

Describe particle behaviour when substances contract

Answer 15

When the particles cool down, they lost the kinetic energy and become slow and closer packed together. This causes the solid/liquid to contract (shrink in size).

Question 16

Explain how melting can be explained using the particle model

Answer 16

Particles in a solid are closely packed. When they are heated they gain kinetic energy, causing them to vibrate more vigorously. As the temperature rises, the energy supplied is enough to overcome the forces holding the particles together, leading to a transition from solid to liquid. Since the bonds holding the particles together were broken, the particles are no longer in a fixed position and are able to move past each other allowing the substance to take a new shape (liquid).

Question 17

Explain how freezing can be explained using the particle model

Answer 17

The particles in a liquid are close together but can move freely. When a liquid is cooled, it’s particles lose kinetic energy and being to slow down. As the temperature drops, the attractive forces between the particles grow stronger, allowing them to arrange the particles into a fixed structure. The substance transforms from a liquid to a solid and the particles become locked in place.

Question 18

Explain how evaporation can be explained using the particle model

Answer 18

The particles in a liquid are close but can move freely. If the surface particles gain enough kinetic energy (usually from heat) it can be enough to overcome the attractive forces holding the liquid particles together. These high-energy particles escape in the air as gas. This can happen until their is no liquid remaining.

Question 19

Explain how condensation can be explained using the particle model

Answer 19

In a gas, particles are widely spaced and can move freely at high speeds. When gas cools or comes in contact with a cooler surface, the particles lose kinetic energy and start to slow down. As they lose energy, the attractive forces between the particles become significant, drawing them closer together. This results in a transition from a gas to a liquid as the particles cluster together.

Question 20

Describe the application of the particle theory of matter using
everyday examples

Answer 20

Particle theory suggests that matter is composed of tiny particles constantly in motion, providing a relatable understanding of everyday phenomena. Solids like ice have tightly packed particles, giving them a definite shape and volume. Liquids like water have particles that can move around each other, allowing water to take its container’s shape while maintaining a consistent volume. Gases like oxygen have far apart particles that move freely, filling any available space without a fixed shape or volume. Temperature plays a significant role in particle motion. Heat increases the movement of water particles, causing boiling and steaming. Conversely, cold temperatures slow down the motion of ice particles, allowing them to absorb heat and melt.

Question 21

Describe examples of gas formation that are chemical

Answer 21

• Vinegar and Baking Soda Reaction: When acid in vinegar reacts with baking soda, carbon dioxide gas is produced, creating bubbles or fizzing.
• Photosynthesis: During photosynthesis, plants convert carbon dioxide and water into glucose and oxygen. The oxygen is released as a gas

Question 22

Describe ways to detect the presence of a new substance

Answer 22

• Fizzes
• Changes Colour
• Changes Temperature
• Production of a gas or a solid