Pure Substances & Mixtures

Name: ____________________________________

Class: _____________________________________

Science 7

Pure Substances & Mixtures Miss Tse

Tse Science 7 Name: __________________________

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Unit 2: Topic 1

Matter in Your World

Matter:

Properties:

Mixture:

Mixture Flow Chart

Tse Science 7 Name: __________________________

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According to our flow chart, there are two categories of mixtures:

1) Heterogeneous (Mechanical) Mixture:

Ex.

2) Homogenous (Solution) Mixture:

Ex.

Tse Science 7 Name: __________________________

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Unit 2: Topic 2

Particle Theory of Matter

Pure Substances:

Ex.

Particle Theory of Matter:

1.

2.

3.

4.

5.

Tse Science 7 Name: __________________________

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What Makes Materials Dissolve?

____________________________: when a solution

is formed by mixing two or more materials

For example, when we mix sugar into water, the

particles of water can attract a sugar particle more

strongly than the other sugar particles around it.

First, the water particles pull a sugar particle away from the other particles. Then the

motion of the water carries it away. This makes room for more water particles to move in

and attract another sugar particle. This process continues until all of the sugar is

dissolved.

Diagram:

When sugar dissolves in water, we call the water the ______________________ and the

sugar the _______________________.

Solute:

Solvent:

Tse Science 7 Name: __________________________

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Why Do Some Materials Not Dissolve?

Insoluble:

Ex.

Mixing materials together does not always result in a _________________.

Why do they not mix together?

This depends on the attraction between the particles.

For example, grass stains are very hard to get out clothing. That is

because the chlorophyll in the grass are more attracted to each

other than the water particles you are putting on it to wash it out.

You would need to use a different solvent that the chlorophyll is

more attracted to!

Tse Science 7 Name: __________________________

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Unit 2: Topic 3

Energy Changes

ENERGY:

- Whenever a change occurs, energy is transferred from one object to another

Energy is a property or quality of an object or substance that gives it the ability to

move, do work, or causes change.

Law of Conservation:

Thermal Energy:

- This is also the total kinetic energy of all the particles in a substance

- Thermal energy can be _____________________ and ______________________

For example: The particles in a hot air balloon

BEFORE HEATING AFTER HEATING

Tse Science 7 Name: __________________________

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Two things you must know about energy:

1. Changes happen when there is a difference of energy

Examples:

2. Energy is always transferred in the same direction

- Energy goes from a ________ energy source to something with ________energy

Heating and Cooling

- Heating anything increases the ____________ energy of all it’s particles

BUT

the _____________ energy of the particles (which is the temperature of

the substance) may increase or stay the same, depending on the number of

particles (the amount of material that is being heated)

- Decreasing the temperature of an item means that the object _________________

the material _________________ the thermal energy.

o This means that there is ___________ energy in the material so the

average motion of the particles slows down

For example: an ice cube in a warm drink

The ice cube will absorb the thermal energy as the soda

cools down. Now the soda will have less energy so particle

movement slows.

Tse Science 7 Name: __________________________

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Unit 2: Topic 4

Expansion and Contraction

As a substance warms up, the particle model of matter states that the particles move faster

and spread apart.

This means that we expect the substance to _______________________ (increase

in volume) as their temperature rises.

As well, we expect that substances will ___________________________

(decrease in volume) as they cool down.

We can check these predictions by using pure substances. A pure substance is:

A pure substance can exist as a ___________________, _____________________, or

_______________.

By testing pure substances, we have learned that substances in a:

- ______________________ State are materials that will keep their shape and size

because solids have a definite shape and cannot be compressed into a smaller

space

- ______________________ State are materials that have a definite size (volume)

but no fixed shape.

o Liquids cannot be compressed

- _______________________ State have no definite shape or volume. They expand

to fill all parts of their container and can be compressed into a small space.

Expansion and Contraction in Liquids

Ex. How a thermometer works

Cold Water Hot Water

Tse Science 7 Name: __________________________

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Unit 2: Topic 5

The Particle Model and Changes of State

Changes of State

Sublimation:

Changes in temperature are signs of changes in particle motion, which means

changes in thermal energy.

Melting and Boiling Points

- The melting and boiling points of a substance are important pieces of information

Melting Point:

Boiling Point:

Substance Melting Point (°C) Boiling Point (°C)

Oxygen -218 -183

Mercury -39 357

Water 0 100

Lead 328 1740

Tse Science 7 Name: __________________________

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What Happens When A Liquid Evaporates?

In a liquid, particles are moving at different speeds.

At the surface of a liquid, the faster moving particles are able to escape into the air. As

the particles leave the liquid, the remaining liquid is cooler than the original liquid.

The slower particles stay in liquid state. If the particles move slower, it means it has

lower energy, meaning lower temperature.

Evaporative Cooling:

REMEMBER: the average speed of the particles does not change because temperature

stays constant during a phase change (ex. Liquid to gas).

The only thing that does change is the arrangement of the particles.

Particles become less organized as their energy increases.

Particles become more organized as their energy decreases.

The total energy of a substance increases or decreases during a phase change. This

happens because the particles are no longer increasing or decreasing their speed, it is the

arrangement of these particles that change.

The average energy of the particles DOES NOT change so the temperature of the

substance stays constant.

Here are some diagrams:

Tse Science 7 Name: __________________________

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Unit 2: Topic 6

Transferring Energy

Energy Source:

There are three ways in which energy can be transferred.

1.

2.

3.

1. Radiation

For example: the sunshine that is powering your calculator is a type of radiation. There is

no physical material that travels from the sun to your calculator.

BUT, even though there is no physical material travelling, there is energy being

transferred.

This is called ____________________________________________ or

_____________________.

It is:

This kind of energy travels through space by the form of ________________. EMR can

travel through empty space, air, glass and many other materials.

There are many different types of EMR such as microwaves, visible light, and X-rays.

Tse Science 7 Name: __________________________

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If the energy source is a warm object like the Sun, it has _________________________.

This energy is transferred as a type of EMR, called infrared radiation.

All radiant energy share several characteristics:

- They behave like waves

- They can be absorbed and reflected by objects

- They travel across empty space at the same very high speed (300 000 km/s)

Reflectors Absorbers

2. Conducting Energy Through Solids (Conduction)

In solids, the particles look like:

Thermal Conduction:

Tse Science 7 Name: __________________________

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Conductors Insulators

When insulators are wrapped around

an object, they slow down the

transfer of thermal energy to or from

the surroundings.

Ex. Ex.

3. Convection

- Thermal energy can be transferred by __________________.

Fluids:

Convection is when:

Why and how are convection currents created?

Tse Science 7 Name: __________________________

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When something is warmed up, the particles move farther apart. Each section of

the warmed materials is left with fewer particles than when it was cold, so that section is

lighter than it used to be, meaning it is less dense.

Cold and dense air sinks down and pushes nearby warm fluid upwards. Then the

cold fluid is warmed up and pushed up as well.

As that warm air rises up and away from the heat, it starts to cool down. When it

cools down, the spaces between the particles contract and makes it become denser. When

it becomes denser, it sinks back down where it gets warmed up again.

The process continues again as a continuous movement.

Transferring Energy

Tse Science 7 Name: __________________________

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Unit 2: Topic 7

Sources of Thermal Energy

Different Types of Energy

1. Chemical Energy

Examples of chemical energy are:

2. Electrical Energy

Examples of electrical energy:

Electricity can be produced at generating stations that burn fossil fuels. Where large dams

cannot exist, fuel-burning generating stations are used to provide electrical energy to

large populations.

- The heated water is a product of these generating stations. This hot water is

released into lakes and rivers that can be dangerous to the organisms living

there.

- Also, the chemicals that released when burning fossil fuels can cause damage

to the environment.

3. Mechanical Forces

Thermal energy can be released due to the impact of physical contact.

Tse Science 7 Name: __________________________

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4. Geothermal Energy

Examples of geothermal energy are:

One technique for using geothermal energy is called HDR (hot, dry rock). Engineers

pump water into rock that has been cracked. The water returns to the Earth’s surface as

steam. This steam is used to generate electricity.

Geothermal energy is clean and is a good alternative to burning fossil fuels since we are

running out of these resources. Also, geothermal energy reduces the wastes that are

produced by mining and burning fossil fuels.

5. Solar Energy

Solar energy is clean and not likely to run out.

Although, one disadvantage of using solar energy is the fact that there are periods of time

where the Sun does not shine.

- Solar energy is not available through the night.

- There is less solar energy available during the winter than summer

a. Passive Solar Heating

b. Active Solar Heating

Tse Science 7 Name: __________________________

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Active solar heating uses complex devices that are called ________________________.

These are usually on the roof of a building and contain water or air. The Sun then heats

the water or air and is then pumped through the building.

6. Wind Energy

Wind energy is a result of solar energy.

As the Sun heats the air, warmer air rises and cools down. The cooler air creates

convection currents. This forms our wind systems.

Wind energy can be harnessed to produce electricity. A turbine does exactly that. The

wind helps rotates an electrical generator that creates electricity.

7. Warm Blooded Organisms - Organisms release energy for their body’s growth and activity. That thermal

energy is transferred to the air and objects around them.

- A composter (decomposer) breaks down food which releases thermal energy

which helps in decomposition

Fossil Fuels

Energy Resource:

Fossil Fuels:

Tse Science 7 Name: __________________________

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There are two major problems with fossil fuels:

1. Society’s use of fossil fuels has increased rapidly over the years.

- As a result, fossil fuels will be very expensive and difficult to obtain

Fossil fuels are considered to be a non-renewable resource. These are:

Renewable resource:

Ex.

2. Another problem is that when fossil fuels are burned, they produce carbon dioxide

gases.

- The amount of carbon dioxide that is being produced ruins natural carbon

dioxide recycling systems such as plants.

- The large amount of carbon dioxide gets stuck in the atmosphere and becomes

a greenhouse gas

Greenhouse gases:

These greenhouse gases contribute to global warming.

Normally, small amounts of carbon dioxide in the atmosphere helps keep the Earth warm

enough to support life. But due to the increased amounts, thermal energy is being trapped

which is warming Earth very quickly.

Due to this warming, lakes and rivers are drying up and icebergs are starting to

melt.

Tse Science 7 Name: __________________________

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Unit 2: Topic 8

Conserving Our Fossil Fuel Resources

We have talked about how dangerous the burning of fossil

fuels is in our class but we still use them. That is because

fossil fuels are a key part of Alberta’s economy.

Coal is burned in generating stations to produce about 80% of Alberta’s electrical

energy! This energy is used within our homes and workplaces. Oil and natural gas are

also very important to Alberta’s economy. This is a reason why we cannot stop using it.

It’s Cold in Here!

Both fridges and air conditioners are ___________________________; this means that it

can transfer thermal energy from one location to another at a different temperature.

Fridges and air conditioners both rely on processes such as __________________ and

_________________.

In a fridge, _________________________ are used to

remove thermal energy from food.

Refrigerants:

Thermal Energy can be Dangerous!

Thermal energy can be harmful, such as burns from a

hot object or a forest fire. Thermal energy has the

power to hurt and destroy us, our belongings, and our environment.

In factories, they must carefully store harmful chemicals in storage tanks to prevent the

chemicals from leaking into the soil and then it will drain into water sources.

The soil that is affected from the chemicals must be restored before it can be used

by anything else again. Millions of dollars are placed into programs that attempt to fix

soil to its natural state.

The __________________ of thermal energy can also be dangerous. Carbon dioxide is a

byproduct which is a greenhouse gas. This contributes to global warming. Sulfur dioxide

is also released and this can be very irritating to the eyes, nose, and throat.

Also, when a fire burns without oxygen, a gas called _____________________ is

produced. It is very dangerous because it is colorless, odorless, and it can kill you. Many

people have died from inhaling this gas. The Government of Canada encourages that

every household have a detector!

Tse Science 7 Name: __________________________

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