chemistry - revision part 2

What are the two types of tiny particles all matter is made from?

Atoms and molecules.

Atoms, which are the basic units of matter, and molecules, which are combinations of two or more atoms bonded together.

Define an atom.

The smallest unit of an element - that retains the properties of that element, consisting of a nucleus surrounded by electrons.

Are particles always moving?

Yes — they are always in motion. This motion occurs even in solids, where particles vibrate in place.

What does heating do to particles?

They gain energy, move faster, spread apart.This increased movement can lead to changes in state, such as melting or boiling.

What does cooling do to particles?

They lose energy, move slower, come closer.This decreased movement can lead to changes in state, such as freezing or condensing.

What determines the state of matter?

The arrangement and movement of particles, including their energy levels, dictate the state of matter, which can be solid, liquid, or gas.

Where are forces between particles strongest?

In solids, where particles are closely packed together.

Where are forces between particles weakest?

In gases. The particles are far apart and move freely, resulting in negligible intermolecular forces.

Why do scientists use particle diagrams?

To explain the behaviour of matter when particles are too small to see. They visually represent the arrangement, motion, and interactions of particles, aiding understanding of different states of matter.

Describe particle arrangement in a solid.

Tightly packed, fixed positions, vibrate only.

The particles are arranged in a regular pattern, closely packed together, and held in fixed positions, allowing them to vibrate slightly.

Describe particle arrangement in a liquid.

Close together, slide past each other, no fixed shape

. The particles are arranged more loosely than in solids, allowing them to move and slide past each other, resulting in a definite volume but no fixed shape.

Describe particle arrangement in a gas.

Far apart, move quickly in all directions.

The particles in a gas are arranged far apart from each other, moving quickly and freely in all directions, leading to no definite shape or volume.

Which state is easily compressed?

Gas state, due to widely spaced particles.

Gases can be easily compressed because their particles are widely spaced, allowing for a reduction in volume when pressure is applied.

Why can gases be compressed but solids cannot?

Their particles are far apart.

in solids, the particles are tightly packed and vibrate in fixed positions, which prevents significant compression compared to gases.

In which state are particles closest together

Solid.

In solids, particles are packed closely together, allowing them to maintain a fixed shape and volume.

Which state has the weakest forces between particles?

Gas.

In gases, the forces between particles are minimal, allowing them to move freely and occupy the available space.

Define melting.

Solid → liquid.

The process in which a solid turns into a liquid when heated, as the particles gain energy and overcome their fixed positions.

What happens to particles during melting?

Gain energy, vibrate faster, break apart.

This allows them to transition from a rigid structure in a solid state to a more fluid and flexible arrangement in a liquid state.

What happens to particles during freezing?

Lose energy, slow down, come together. This process transforms them from a liquid state into a solid structure.

Define freezing.

The process in which a liquid turns into a solid as it loses energy, causing the particles to slow down and arrange into a fixed structure.

Define boiling.

The process in which a liquid turns into a gas as it gains energy, causing the particles to move rapidly and break free from the liquid's surface.

Define evaporation.

Slow liquid → gas from surface.

This process occurs at temperatures below boiling, where molecules at the surface gain enough energy to enter the gas phase.

Define condensation.

Gas → liquid.

This process occurs when gas molecules lose energy, slowing down and coming together to form a liquid.

Define sublimation.

Solid → gas (skipping liquid).

The process in which a solid turns directly into a gas without passing through the liquid phase, often occurring under low pressure and/or high temperature.

Example of a substance that sublimates.

Dry ice (solid carbon dioxide)

Dry ice or iodine.is an example of a substance that sublimates, transitioning directly from solid to gas.

What is boiling point?

The temperature at which a liquid rapidly turns into a gas.

What happens to particles when heated?

Gain energy, move faster, spread further apart.

When particles are heated, they gain energy, causing them to move faster and spread farther This increase in kinetic energy results in a change of state for substances as they may transition from solid to liquid or liquid to gas. apart. .

What happens to particles when cooled?

Lose energy, move slower, move closer.

When particles are cooled, they lose energy, slowing their motion and bringing them closer together. This decrease in kinetic energy can result in a change of state, leading to transitions from gas to liquid or liquid to solid.

Define diffusion

Particles spreading out and mixing without stirring.

This process occurs due to the random motion of particles, leading to an even distribution in a medium, such as a gas or liquid.

Why does diffusion happen faster in gases?

Gas particles move faster and are farther apart.

This increased kinetic energy allows for more frequent collisions and interactions, leading to quicker mixing and dispersion.

Why aren't liquids easily compressed?

Particles are already close together. The close packing of particles in liquids means there is little empty space to compress, making them much less compressible than gases.

Which state is easiest to compress?

Gas.

Gas particles have significant space between them, allowing for easy compression.

Define a physical change.

A change that affects one or more physical properties of a substance without altering its chemical composition.

No new susbatnce is formed.

Define a chemical change.

A new substance is formed.

This change involves a transformation where the original substances undergo a chemical reaction, resulting in different properties and a new chemical identity.

Give examples of physical changes.

Melting butter, boiling water, and dissolving sugar.

Give examples of chemical changes.

Burning wood, rusting iron, and baking a cake. reactions with acids.

Signs of chemical change (give two).

Gas produced, colour change, precipitate formed, temperature change. Examples include bubbles forming and a colour shift.

Why is rusting a chemical change?

A new substance (iron oxide) is formed.

It involves a chemical reaction between iron, oxygen, and moisture, resulting in a new substance iron oxide.

Is melting chocolate physical or chemical?

Melting chocolate is a physical change because it alters the state of matter from solid to liquid without changing its chemical composition.

What is a precipitate?

A solid formed when two solutions react.

What is effervescence?

Bubbles/fizzing when gas is released.

It occurs during a chemical reaction where gas is produced, such as when an acid reacts with a carbonate.

Example of effervescence reaction?

Acid + carbonate → CO₂.

An example of effervescence is the reaction of vinegar (acetic acid) with baking soda (sodium bicarbonate), producing carbon dioxide gas and causing bubbling.

What colour precipitate forms when copper sulphate reacts with sodium hydroxide?

A blue precipitate of copper(II) hydroxide forms when copper sulfate reacts with sodium hydroxide.

What colour precipitate forms when iron(II) sulphate reacts with sodium carbonate?

A green precipitate of iron(II) carbonate forms when iron(II) sulfate reacts with sodium carbonate.

Exothermic reaction means…?

Energy/heat is released. This type of chemical reaction releases energy, usually in the form of heat, resulting in an increase in the temperature of the surroundings.

Endothermic reaction means…?

Energy/heat is absorbed during this type of chemical reaction, resulting in a decrease in the temperature of the surroundings.

What ending is used for 2-element compounds?

The suffix '-ide' is used. This suffix indicates that the compound consists of two elements, typically a metal and a non-metal.

What ending is used for compounds containing oxygen?

The suffix '-ate' or '-ite' is used depending on the oxidation state of the metal.

sodium + chlorine makes…

sodium chloride, or table salt.

magnesium + oxygen makes…

magnesium oxide

iron + sulfur makes…

iron sulfide or ferrous sulfide.

sodium + nitrogen + oxygen makes…

Sodium nitrate.A chemical compound formed by combining sodium, nitrogen, and oxygen.

lithium + nitrogen + oxygen makes…

:Lithium nitrate.

What does the ending –ate tell you?

The compound contains oxygen.

Specifically, it indicates that the compound is a salt of an acid containing oxygen, known as an oxyanion.

Write the word equation for magnesium burning in oxygen.

magnesium + oxygen → magnesium oxide

Reaction: metal + oxygen → ?

Metal oxide

Reaction: acid + carbonate → ?

Salt + water + carbon dioxide.

This reaction describes the process by which an acid reacts with a carbonate, forming a salt, water, and carbon dioxide gas.

Reaction: acid + metal → ?

Salt + hydrogen gas.

This reaction describes the process by which an acid reacts with a metal, producing a salt and releasing hydrogen gas.

Reaction: acid + alkali → ?

Salt + water.

This reaction describes the neutralization process where an acid reacts with a base (alkali) to produce salt and water.

copper sulphate + sodium hydroxide → ?

Copper hydroxide + sodium sulphate.

This reaction describes the process where copper sulfate reacts with sodium hydroxide to form copper hydroxide, a precipitate, and sodium sulfate, a soluble salt.

Products of calcium carbonate + hydrochloric acid?

Calcium chloride + water + carbon dioxide.

This reaction involves calcium carbonate reacting with hydrochloric acid, resulting in the formation of calcium chloride, water, and carbon dioxide gas.