# 1.1 - 1.7 The three states

#### 1.1 Introducing the states

Solid, liquid or gas?

Matter can exist in one of three fundamental states: Solid, Liquid or Gas

Here we consider the way in which these three states behave

We see how matter can be converted from one state into another and we introduce the terms used for these changes.

Evaporation, condensation, melting, freezing , sublimation and deposition.

It is important to be able to recall and explain the properties and behaviour of solids liquids and gases.

We also look at the way in which some substances dissolve in others and consider the terms :

#### 1.1 - 1.2 Three fundamental states of matter

The three primary states of matter

#### Students should:

1.1 understand the three states of matter in terms of the arrangement, movement and energy of the particles

1.2 understand the interconversions between the three states of matter in terms of:

• the names of the interconversions
• the names of the interconversions
• how they are achieved
• the changes in arrangement, movement and energy of the particles.

#### 1.2 Activity 1: Properties of the states

All matter is made up of particles. In solids, liquids and gases, the particles might be ions, molecules or atoms

Watch the first 70 seconds of the video. Use your own words to describe the motion of the particles, the behaviour, shape and volume of a material when it is a :

• ​solid
• liquid
• gas
• ​In a solid the particles vibrate but the solid remains in a fixed shape. The solid has a fixed density and cannot be compressed
• In a liquid the particles have enough energy to move freely and the liquid can therefore flow. A liquid will take up the shape of the container in which it is placed. The liquid cannot easily be compressed.
• In a gas the particles are widely spaced and move freely. The gas will fill the container in which it is placed. Gases can be compressed.

#### 1.2 Activity 2: Name the changes

Can you name processes 1, 2, 3 and 4?
Four changes of state. Which two terms are missing?

Heating a material will give energy to its particles and cause them to move more rapidly. Cooling does the opposite. Heating or cooling can therefore cause a material to undergo a change of state.

With three principal states of matter there are six possible changes depending on whether we are heating or cooling the substances. These are shown in the table below.

 ​ ​Heating ​Cooling ​solid/liquid ​melting ​freezing ​liquid/gas ​evaporating ​condensing ​solid/gas ​sublimation ​deposition
Add arrows and labels to a copy of this image to show the six changes of state discussed in the video and shown in the table

#### 1.3 Activity 4. A particular problem

Particle theory explains why the smell of cooking in the kitchen can quickly be smelt by people in other rooms.

#### Students should:

1.3 understand how the results of experiments involving the dilution of coloured solutions and diffusion of gases can be explained

Particle theory states that all matter consists of many, very small particles which are constantly moving or in a continual state of motion. This theory helps us to explain how food colouring dissolves in water so that the colour spreads evenly throughout.

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration

Diffusion happens in liquids and gases because their particles move randomly from place to place. Diffusion is an important process for living things; it is how substances move in and out of cells.

#### 1.4 Activity 5 : Defining diffusion, diluting and dissolving

​Gases can diffuse into each other . This is because the particles in a gas are in a state of constant random motion.

Liquids can diffuse into other liquids. When the two liquids mix well in each other they are said to be soluble.The diffusing of one liquid ( the solute) into another ( the solvent) results in the dilution of the solute by the solvent.

The food colouring video here shows dilution in action.

• Dilution Open or Close

Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to a solution.

• Diffusion Open or Close

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.

• Dissolving Open or Close

Solids, liquids, and gases can all dissolve. Dissolving depends on the molecules of the substance doing the dissolving, called the solvent, and the molecules of the substance being dissolved, called the solute. Dissolving is the process in which these molecules interact and attract each other to form a solution.

Watch  both the video and the animation carefully.

• Describe what happens.
• Try to explain what happens
• Explain why the colour spreads faster in the hot beaker

Use the each of the following words at least once:

food colouring, dissolve, particles , constant motion, soluble, water , faster , diffuse , diluted

#### Students should:

1.4 know what is meant by the terms: solvent, solute, solution, solution, saturated solution.

1.5C know what is meant by the term solubility in the units g per 100 g of solvent

1.6C understand how to plot and interpret solubility curves

1.7C practical: investigate the solubility of a solid in water at a specific temperature

Watch the video carefully and write down your answers to the questions before revealing them by clicking on each questions in turn.

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