UNIT 2 – MATTER AND ITS PROPERTIES

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INDEX

1. What is matter

2. States of matter

Macroscopic approach

Microscopic approach, kinetic theory

Changes of state

3. Properties of matter

General properties

Mass, volume, temperature....

Characteristic properties

Density

Boiling point

Melting point

4. The gaseous state

Boyle’s law

Charles’ law

Gay –Lussac’s law

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1.WHAT IS MATTER?

Matter is everything that has mass, occupies a volume and has

properties that can be measured.

2.STATES OF MATTER

Macroscopic approach:

SOLIDS:

• They have a fixed volume ( they can´t be compressed)

• They have a fixed shape

• They can´t flow

LIQUIDS

• They have a fixed volume (they can be slightly compressed)

• They take the shape of the container

• They can flow

GASES

• They fill the whole container. They have an indefinite volume.(they

can be compressed)

• They take the shape of the container. They have an indefinite shape

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Microscopic approach: Kinetic matter theory:

SOLIDS:

• Particles of solids are tightly packed in a regular pattern.

• Particles vibrate around a fixed position.

• Particles are strongly attracted to each other.

LIQUIDS

• Particles of solids are randomly packed (In a mess)

• Particles can move around.

• Particles are attracted to each other.

GASES

• Particles of gases don´t touch each other

• Particles can move around fast in all directions

• The forces of attraction are very weak.

Microscopic Explanation of Properties of Solids

Solids have a definite shape and a definite volume because the

particles are locked into place

Solids are not easily compressible because there is little free space

between particles.

Solids do not flow because the particles cannot move and the forces

between them are very strong.

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Microscopic Explanation of Properties of Liquids

Liquids have an indefinite shape because the particles can slide past

one another.

Liquids are not easily compressible and have a definite volume

because there is little free space among the particles.

Liquids flow easily because the particles can move and the forces

between them are not so strong.

Microscopic Explanation of Properties of Gases

Gases have an indefinite shape and an indefinite volume because the

particles can move past one another.

Gases are easily compressible because there is a great deal of free

space between particles.

Gases flow very easily because the particles randomly move and the

forces between them are very weak.

Changes of state

The names for the changes are:

The change from liquid to solid is solidifying (in the case of water is

freezing)

The change from solid to gas is sublimation

The change from gas to solid is deposition

Language:

The names of some changes end in –ing: melting, boiling, condensing,

freezing, solidifying.

But we say sublimation and deposition!

When we are speaking about a substance (for example water) we say :

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It melts, it boils, it freezes, it condenses, it solidifies, it sublimates.

When a liquid becomes a gas (in general we call it vaporisation), it can

happen in two ways:

Evaporation:

It happens when only the particles on the surface of the liquid

become a gas.

It happens at any temperature.

Boiling:

It happens when particles throughout the liquid become bubbles of

gas and rise to the surface and escape from the liquid.

It happens at a certain temperature for each liquid.

When water is in the gaseous state we call it steam.

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3.PROPERTIES OF MATTER

We can classify the properties in two groups:

General properties

Characteristic properties

General properties:

They are physical features that describe matter but can change

without changing the substance.

Examples: size, shape, texture, temperature, state, volume.

Characteristic properties:

They are fixed properties that do NOT change, they have always the

same value for the same substance

Examples: boiling point, melting point, solubility, conductivity,

hardness ,pH, flammability, density.

In this unit we are going to study:

Density

Boiling point

Melting point

As characteristic properties are not affected by physical changes, they

can be used to identify matter

DENSITY

Density = amount of matter per volume unit.

D = m/v (g/cm3)

• Mass is usually expressed in grams

• Volume is usually expressed in cm3 or liters, etc.

So the units can be:

g/ml g/ cm3 Kg/l Kg/m3

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MELTING POINT

It is the temperature at which a solid becomes a liquid.

It always happens at the same temperature.

It is also the temperature at what a liquid becomes a solid.(freezing)

BOLILING POINT

It is the temperature at which a liquid becomes a gas.

It happens always at the same temperature.

It is also the temperature at which a gas becomes a liquid.(condensing)

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Language:

Here you have several verbs that you can use to describe the curves:

To turn into

To increase

To rise

Rise X raise

The sun rises.

Please raise your hand

Each substance has a certain melting point and a certain boiling point:

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4.THE GASEOUS STATE

The kinetic matter theory explains that:

A gas is composed of small particles.

The particles have an insignificant volume and are far apart from one

another.

There is empty space between particles.

Little attractive forces between particles.

The particles in a gas move in constant random motion.

Particles path is only changed by colliding with another particle or

the sides of its container.

Gases have several properties:

They exert pressure:

Gas particles exert pressure by colliding with objects in their path.

The sum of all of the collisions makes up the pressure the gas

exerts.

There are several units for measuring pressure :

Atmospheres (atm)

Millimeters of Mercury (mmHg)

Gases occupy volume:

The volume of the gas is simply the volume of the container it is

contained in.

The metric unit of volume is the cubic metre (m3)

Gases have temperature:

The temperature of a gas is generally measured with a thermometer

in Celsius.

All calculations involving gases should be made after converting Celsius to

Kelvin temperature.

Kelvin = C° + 273

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GASES LAWS

Studies of the behavior of gases have become mathematical laws

which we can use to predict quantitative outcomes.

BOYLE´S LAW

Robert Boyle observed the relationship between pressure and volume

of a gas.

During his experiments, temperature and the amount of gas weren’t

allowed to change

Boyle’s Mathematical Law: PV = k

What if we had a change in conditions?

since PV = k

At constant temperature the volume of a gas is inversely roportional

to the pressure.

As volume increases, pressure decreases.

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CHARLES’S LAW

Jacques Charles determined the relationship between temperature

and volume of a gas.

During his experiments, pressure of the system and amount of gas

were held constant.

Charles’s Mathematical Law: V/T = k

What if we had a change in conditions?

since V/T = k

At constant pressure the temperature of a gas is directly proportional to

the volume.

As temperature increases, volume increases.

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GAY-LUSSAC´S LAW

Lussac determined the relationship between temperature and

pressure of a gas.

During his experiments volume of the system and amount of gas were

held constant.

The pressure increases when temperature increases because the

molecules are moving faster and colliding against the sides of their

containers more often.

Therefore, the pressure inside that container is greater, because

there are more collisions.

Lussac’s Mathematical Law: P/T = k

What if we had a change in conditions?

since P/T = k

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At constant volume the temperature of a gas is directly proportional to the

pressure.

As temperature increases, pressure increases.

UNIT 2 - MATTER AND ITS PROPERTIES.

Activities

A1-States of matter. ( listening activity)

You are going to listen to a text and you have to fill the bubbles of the

“mind map”.

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A2-States of matter (speaking activity)

Help yourself with this chart:

Key words (one or two in each

cell)

How are they packed?

How do they move?

How are them attracted to

each other?

Now, without any help say sentences about particles and your

partner has to guess which state you are speaking about:

A3-Changes of state ( writing and speaking activity)

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A4-Evaporation and boiling

A5-Changes of state (writing and speaking activity)

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A6-Density

A7-Density

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A8-Density

A9-Density (writing and speaking activity)

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A10-Density

A11-Changes of state

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A12-Changes of state (Writing and speaking activity)

First answer these questions and then you will have to explain

them out loud to a partner:

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A13 - changes of state

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A14-Pressure

A15-Gases Laws (Language activity)

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A16-Gases laws (Language activity)

A17-Gases laws (writing and speaking activity)

A18-Gases laws

1 litre of a gas at standard temperature (T=cte) and

pressure is compressed to 473 mL. What is the new

pressure of the gas?

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A man heats a balloon in the oven. If the balloon initially

has a volume of 0.4 liters and a temperature of 20 0C, what

will the volume of the balloon be after he heats it to a

temperature of 250 0C?

If I initially have a gas at a pressure of 12 atm, a volume of

23 liters, and a temperature of 200 K, and then I raise the

pressure to 14 atm and increase the temperature to 300 K,

what is the new volume of the gas?

UNIT 2-MATTER AND ITS PROPERTIES

EXERCISES

1

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2

3

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4

5

6 What is the density of a piece of wood that has a mass of 25.0 grams and a volume of 29.4 cm3?

7 A piece of wood that measures 3.0 cm by 6.0 cm by 4.0 cm has a mass of 80.0 grams. What is the

density of the wood? Would the piece of wood float in water? (volume = L x W x H)

8 A cup of gold colored metal beads was measured to have a mass 425 grams. By water displacement,

the volume of the beads was calculated to be 48.0 cm3. Given the following densities, identify the

metal.

Gold: 19.3 g/mL

Copper: 8.86 g/mL

Bronze: 9.87 g/mL

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9 I threw a plastic ball in the pool for my dog to fetch. The mass of the ball was 125

grams. What should be the volume to have a density of 0.500 g/mL.?

10 The density of aluminium is 2.70 g/mL. If the mass of a piece of aluminium is 0,244 Kg,

what is the volume of the aluminium?

11

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12

13

14

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16

17

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21

22

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25

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26

Write in right order the particle diagrams

27 If I initially have a gas with a pressure of 84 kPa and a temperature of 350 C and I heat it an additional 230 degrees, what will the new pressure be? Assume the volume of the container is constant.

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28 My car has an internal volume of 2600 liters. If the sun heats my car from a temperature of 200 C to a temperature of 550 C, what will the pressure inside my car be? Assume the pressure was initially 760 mm Hg.

29 A toy balloon filled with air has an internal pressure of 1.25 atm and a volume of 2.50 L. If I take the balloon to the bottom of the ocean where the pressure is 95 atmospheres, what will the new volume of the balloon be? How many moles of gas does the balloon hold? (Assume T = 285 K)

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LABORATORY - COOLING CURVE.

Work in groups of three people.

You are going to read the following instructions. First, cut the pictures

bellow with the scissors. Then, follow the instructions moving the pictures

and doing exactly what you are asked to do.

Finally show the teacher how you did it. Ask any questions you are

interested in, before carrying out the experiment.

Instructions:

Put the gauze on the top of the gas heater.

Put a beaker over the gauze and fill it with water.

Put 5 grams of naphthalene into a Pyrex test tube.

Add a thermometre to the test tube.

Insert the test tube in a 500 ml beaker of water.

Stick the test tube to a stand with a clamp in order to put it vertically and

inside the water, without touching the beaker.

Light the gas heater.

Heat the naphtalene until it melts

Switch off the heater and remove the heater from the water bath.

Record the temperature of the naphtalene every 15 seconds while it is

cooling. Remember to stir the naphtalene with the thermometre gently.

Stop measuring the temperature when it gets to 70 degrees.

Draw the cooling curve representing the temperature/time data.

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GLOSSARY

boiling [ˈbɔɪlɪŋ] characteristic [ˌkærɪktəˈrɪstɪk] curve [k3ːv] evaporation [ɪˌvæpəˈreɪʃən] flow [fləʊ] indefinite [ɪnˈdefɪnɪt] liquid [ˈlɪkwɪd] matter [ˈmætər] naphthalene [ˈnæfθəliːn] particle [ˈpɑːtɪkl] pressure [ˈpreʃər] raise [reɪz] rise [raɪz] solidify [səˈlɪdɪfaɪ] sublimation [ˌsʌblɪˈmeɪʃən] vaporization [ˌveɪpərəɪˈzeɪʃən] volume [ˈvɒljuːm]