Introductory Pages

Question 1

Usability of materials

Answer 1

Some elements and compounds are naturally found and used in their native state.

Such examples are gold which is used in jewellery and limestone (calcium carbonate) is used in the building industry.

Question 2

Obtaining substances from other chemicals

Answer 2

Other substances are obtained from other chemicals by using different chemical reactions.

For example, iron(III) oxide, also known as haematite, contains iron which has many uses in various alloys and structures. However, iron needs to be extracted from iron(III) oxide before it can be of any use. Therefore, iron(III) oxide needs to be chemically changed to iron metal.

Question 3

Physical changes

Answer 3

When a physical change happens, no new substances are formed.

These physical changes are often changes in state such as melting, freezing, boiling, and condensing. A physical change is a change to a sample of matter in which some properties of the material change, but the identity of the material does not. Physical changes that involve a change of state are reversible.

Question 4

Example of reversible physical change

Answer 4

For example, when liquid water is heated, it changes to water vapour. Even though the physical properties have changed, the molecules are the same as before. This change is reversible. Likewise, melted ice may be refrozen, so melting is a reversible physical change as well.

Question 5

Molecules of water during changes of state

Answer 5

The diagram shows that the molecules of water do not change when it undergoes changes of state.

Question 6

Reversible change of dissolving a salt in water

Answer 6

Dissolving a salt in water is a reversible change since the mixture can be easily separated using physical separation techniques.

Question 7

Just remember that you can do it, future doctor. Sending lots of love .

Question 8

What happens when a chemical change occurs?

Answer 8

Matter is neither created nor destroyed. Instead, the particles of a substance rearrange themselves to form new chemicals.

Question 9

What happens to a substance during a chemical change?

Answer 9

A substance with a certain set of properties changes into a different substance with different physical and chemical properties.

Question 10

What do substances that react together form?

Answer 10

Substances that react together (reactants) form new substances (products).

Question 11

What are some indicators of a chemical change?

Answer 11

Production of light (flame), effervescence (production of gas bubbles), change in smell, change in colour, temperature change, and products formed may have a different state of matter than the reactants.

Question 12

What is an example of a chemical change?

Answer 12

An example of a chemical change is burning LPG on a stove, resulting in the formation of new chemicals (carbon dioxide and water vapour).

Example sentence: When LPG is burned, it produces carbon dioxide and water vapour.

Question 13

What is the law of conservation of mass?

Answer 13

During chemical or physical changes, mass is conserved, meaning that matter is neither created nor destroyed.

Question 14

What is the total mass relationship between reactants and products in a chemical reaction?

Answer 14

The total mass of the reactants is equal to the total mass of the products.

Question 15

Why is the total number of elements on both sides of a chemical reaction equal?

Answer 15

In a chemical reaction, the total number of elements on the left-hand side is equal to the total number of elements on the right-hand side. This is due to the law of conservation of mass.

Question 16

What are the three states of matter?

Answer 16

Solids,liquid and gas

Question 17

How do the shape of solids,liquids and gases differ?

Answer 17

Solids=have a fixed shape and volume
Liquids=take the shape of the container but have a fixed volume
Gases= of not have a fixed shape of volume and will expand in their container

Question 18

Describe the volume characteristics of solids,liquids and gases.

Answer 18

Solids: have a fixed volume
Liquids:have a fixed volume but take the shape of the container
Gases: do not have a fixed volume and will expand to fill the available space

Question 19

Why are gases more compressible than solids and liquids?

Answer 19

Gases are more compressible because there is a lot of space between the particles, allowing them to be pushed closer together. In contrast, particles in solids and liquids are much closer together, making them less compressible.

Question 20

Explain the arrangement of particles in solids, liquids, and gases.

Answer 20

In solids, particles are tightly packed in a
fixed, orderly arrangement.
• In liquids, particles are close together but can move past each other, allowing the liquid to flow.
In gases, particles are tar apart and move
freely, filling the available space.

Question 21

How does the kinetic theory of matter relate to the states of matter?

Answer 21

The kinetic theory of matter states that all matter is made up of particles in constant motion. The amount of kinetic energy these particles have determines their state: solids have the least kinetic energy, liquids have more, and gases have the most.

Question 22

What role do forces of attraction play in the properties of solids, liquids, and gases?

Answer 22

1)In solids, strong forces of attraction hold the particles closely together in a fixed position.
2)In liquids, the forces of attraction are weaker than in solids, allowing particles to move past each other.
3)In gases, the forces of attraction are very weak, allowing particles to move freely and spread out.

Question 23

What is the significance of kinetic energy in the behavior of particles in different states of matter?

Answer 23

Kinetic energy determines the movement and arrangement of particles in different states of matter. Higher kinetic energy means particles move more freely and are less tightly bound, as seen in gases, while lower kinetic energy means particles are more tightly bound and move less, as seen in solids.

Question 24

How does temperature affect the volume of gases?

Answer 24

As the temperature increases, the kinetic energy of gas particles increases, causing them to move faster and spread out more, which increases the volume of the gas.

Question 25

Why do liquids flow more easily than solids?

Answer 25

Liquids flow more easily than solids because the particles in liquids can move past each other, whereas the particles in solids are fixed in place and cannot move freely.

Question 26

What process is depicted by the transition from ice to liquid?

Answer 26

Melting

Question 27

Which change of state involves heat energy being taken from the environment?

Answer 27

Sublimation (solid to gas), melting (solid to liquid), and evaporation (liquid to gas).

Question 28

What term describes the transition from vapor to liquid?

Answer 28

Condensation

Question 29

During which process is heat energy released back into the environment?

Answer 29

Freezing (liquid to solid), condensation (gas to liquid), and deposition (gas to solid).

Question 30

What happens to particles when a solid is heated?

Answer 30

When a solid is heated, the particles vibrate faster as they gain kinetic energy and the attractive forces between particles are weakened.

Question 31

Describe the process of melting.

Answer 31

Melting occurs at the melting point where the attractive forces are no longer able to hold the particles in an ordered array. The solid then changes to the liquid state and becomes a liquid as its temperature increases beyond its melting point.

Question 32

What is boiling?

Answer 32

Boiling occurs at the boiling point at a fixed temperature (boiling point), where throughout the liquid, particles are gaining enough energy to overcome attraction of other particles and form bubbles of gas that rise to the surface.

Question 33

Explain evaporation.

Answer 33

Evaporation occurs at any temperature when there is exposure of a liquid to air that occurs on the surface of a liquid. During this process, only top energetic molecules break free forming gas (vapor). This process can be observed by naked eye evaporation occurring where there’s excess slowly evaporating liquid molecules enveloped around.

Question 34

What happens to liquid particles when they are cooled?

Answer 34

When liquid particles are cooled, they lose kinetic energy and become more strongly attracted to each other, eventually forming a solid.

Question 35

What is sublimation?

Answer 35

Sublimation is the process where some solids turn directly into a gas without passing through the liquid state.

Question 36

Give an example of a substance that undergoes sublimation.

Answer 36

An example of a substance that undergoes sublimation is dry ice (solid carbon dioxide).

Question 37

Describe the process of condensation.

Answer 37

Condensation is the process where gas particles lose kinetic energy, slow down, and come closer together to form a liquid.

Question 38

What is the difference between the arrangement of particles in a solid and a liquid?

Answer 38

In a solid, particles are closely packed in an ordered arrangement with very little movement, whereas in a liquid, particles are less tightly packed and can move around more freely

Question 39

What is deposition in terms of phase changes?

Answer 39

Deposition is the process where a substance transitions directly from the gas phase to the solid phase without passing through the liquid phase.

Question 40

What does a heating curve represent?

Answer 40

A heating curve represents the change in temperature of a substance as it is heated, showing the transitions from solid to liquid and then from liquid to gas.

Question 41

How can you determine if a substance is in a solid state?

Answer 41

If the given temperature is less than the melting point of the substance, it will be in a solid state.

Question 42

What state is a substance in if its temperature is between its melting and boiling points?

Answer 42

The substance will be in a liquid state.

Question 43

At what temperature is a substance considered to be in a gaseous state?

Answer 43

If the temperature is higher than the boiling point of the substance, it will be in a gaseous state.