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1841 DILKUSHA GIRLS SCHOOL LESSON NOTES

Subject: Basic Science Year: 7

Strand 2-Matter

Sub-Strand 2.2-Materials

Content Learning Outcome

S7.2.2.1- Investigate the difference between pure substance and mixture/solutions, S7.2.2.2- Investigate difference between solutions and pure liquid and its importance and its effect on the environment.

Notes:

Pure Substances

- are elements or compounds that cannot be physically separated.

Examples: water, carbon monoxide, oxygen.

Mixtures

-are made up of two or more substances that are together in the same place but are not chemically combined.

-This means they can be separated physically (handpicking/ sieving/evaporation/distillation/filtration or

sedimentation/separating funnel)

Examples: soil, sugar, solution and water.

Solution

-A solution has two parts: the solid which is dissolved is called the solute and the liquid that does the dissolving is

called the solvent.

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Example; solute + solvent = solution

3 Types of Solution

Pure Liquids -Are liquids that do not contain any other form of liquid substance. They do not chemically combine with any other substance. -Impure liquids when heated leave behind substances called residue.

Activity

Complete the following.

1. A solution is made when one substance known as the _______________ is dissolved in another known as

the ______________________. In a cup of coffee, the coffee beans are the _____________ and the water

is ____________________________.

2. A concentrated solution _____________________________________________________.

3. A dilute solution __________________________________________________________.

4. (Experiment in pp.71-72)

5. With the help of a diagram, differentiate between a pure substance and a mixture.

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Strand 2-Matter

Sub-Strand 2.3- Reactions

Content Learning Outcome

S7.2.3.1- Investigate the changes when matter reacts and differentiate between reversible and irreversible reaction.

Notes: Changes of State

1. Substances can change from solids to liquids to gases as they get more energy. For example, ice (solid) can

change to water (liquid), then to steam or vapour (gas).

2. Similarly, we can change gases into liquids and then into solids by taking energy away, that is by cooling

them down. For example, water vapour (gas) on cooling changes into water (liquid) which on further cooling

changes into ice (solid).

3. In most substances this process is reversible. It can happen either way because it is a physical change. 4. An example of physical reaction is the water cycle given below,

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Activity

5. In your own words, differentiate between physical and chemical reaction/ change. Support your

answer with examples.

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Strand 3-Energy

Sub-Strand 3.1- Energy Source and Transfer

Content Learning Outcome

S7.3.1.1- Investigate and illustrate the different energy sources and their uses and classify them into renewable and non-renewable.

Notes: Energy

Everything needs energy in order to move.

It is the capacity to move or the ability to work.

People use energy to think, move and even sleep.

For lights to turn on, they need electricity and electricity needs power in order to flow and turn on

electrical appliances.

Energy can never be created nor destroyed, it only changes form.

Potential and Kinetic Energy

1. Energy comes from many sources but will eventually fall into two categories, potential and kinetic energy.

2. Any energy that is stored in an object is called potential energy. The moment that particular object moves, energy is now changed into kinetic energy.

3. For example, the food you eat contains chemical energy, and your body stores this energy until you use it when you work or play.

Activities

1. Define energy -

____________________________________________________________________________________

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2. Explain how potential energy changes into kinetic energy.

____________________________________________________________________________________

3. Give 2 examples of potential and kinetic energy.

____________________________________________________________________________________

____________________________________________________________________________________

Strand 3-Energy

Sub-Strand 3.2- Energy Transformation, Use And Conservation

Content Learning Outcome

S7.3.2.1- Explore the different forms of energy and their uses and discuss conservation of renewable and non-renewable energy sources.

Renewable Energy Sources

Renewable energy is the energy which is generated from

natural sources and can be generated again and again as

and when required.

They are clean because they do not emit any greenhouse

gases.

It is cheap and readily available.

1. Sun Energy

Solar energy is radiant heat and light sourced from the sun.

Most of the energy used on Earth comes from the sun.

It can be used for heating, electricity, etc.

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2. Water Energy

Hydropower is the production of electrical power through the use of gravitational force of falling or

flowing water.

It is commonly used for electricity.

3. Wind Energy

Wind power is the transformation of wind energy into a useful form of energy.

For instance, using wind turbines to make electrical energy, windmills for mechanical power, wind

pumps for water pumping or drainage, or sails to propel ships.

4. Wood Energy (Biomass)

Often refers to plants or plant-derived materials.

It can be used directly to produce heat.

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5. Geothermal Energy

It is energy generated by converting hot water or steam from deep beneath the Earth’s surface into

electricity.

Non-Renewable Energy Sources

A non-renewable source is a natural source that cannot be

remade or regrown at a scale comparable to its use.

It is very expensive and is limited in use.

Non-renewable energy sources produce a lot of carbon

footprint which enhances greenhouse effect.

Carbon footprints are the carbon dioxide released into the air

when fossil fuels are used or burnt.

More fossil fuels used mean more carbon footprints, depleting

the ozone layer and is eventually harming the environment.

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1. Fossil Fuels

Fossils are the skeletal remains of organisms (plants and animals) that lived on Earth (land and sea) millions

of years ago.

These fossils therefore form coal and petroleum (oil) which are being used today.

The 3 types of fossil fuels are coal, crude oil and natural gas.

Coal-is formed from trees or dead plants preserved below the land.

Oil and natural gas-is formed from dead animal bodies preserved underwater.

Crude oil is extracted and then separated into various fuels like diesel, kerosene, etc.

Different Forms of Energy

The Law of Conservation of energy states that energy cannot be created or destroyed. Energy takes on

many forms and energy within a system is constant. [James Joules]

It can be converted or transformed into many forms depending on the appliance or medium used.

The various forms of energy include electrical, chemical, light (radiant), heat(thermal), mechanical

and nuclear energy.

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Energy Transformation

Energy transformation, also known as energy conversion, is the process of changing energy from one

form to another.

Here are examples of how energy is transformed;

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Activity

1. Differentiate between renewable and non-renewable energy.

____________________________________________________________________________________

____________________________________________________________________________________

2. Identify and illustrate at least 3 energy sources and its importance.

3. Where do we get coal and oil from?

____________________________________________________________________________________

____________________________________________________________________________________

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4. Why is it best to use solar power than fossil fuels?

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5. Describe two advantages and disadvantages of wind energy.

____________________________________________________________________________________

____________________________________________________________________________________

6. Copy and complete.

7. Complete the following by writing the energy in and energy out.

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Strand 3-Energy

Sub-Strand 3.2- Energy Transformation, Use And Conservation

Content Learning Outcome

S7.3.2.2- Explore the importance of good energy management

Energy Conservation (Saving)

Energy is very important for life, for cooking, heating, security and for doing work.

Without energy, life and movement will not exist, therefore we need to use the present energy wisely for

a healthier future.

We can save energy at home by;

Switching off all lights and power points when not in use.

Using electrical appliances when the need arises.

Changing faulty light bulbs.

Not leaving refrigerator door open.

Opting for solar power or using renewable energy sources.

Alternative Energy Sources

- Alternative energy sources refer to other sources that are still being developed.

- This energy source is recommended to be used because the following;

Cost effective

Cause less damage to the environment.

Do not produce polluting substance/ carbon footprints into the atmosphere.

Examples:

Hydroelectric energy (water)

Tidal energy (ocean waves)

Geothermal energy (heat inside the earth)

Solar energy (sun)

Biomass energy (use of organic materials)

Aeolic energy (wind)

Biogas energy (use of food waste)

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Activity

1. Copy the statements and write TRUE or FALSE next to each.

a) Home electricity bill can be less if you keep all your lights on all night. ________________

b) Cooking gas is renewable energy. ________________

c) The more electrical appliances used at home the less energy consumed. ________________

d) Fuels used by machines cause pollution and health risks. ________________

e) Energy eaters at school can use less energy if we maintain them sensibly. ________________

2. Fill in the blanks.

3. Identify an alternative energy source that you recommend to be used. Give a reason for your choice.

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Strand 3-Energy

Sub-Strand 3.3- Forces

Content Learning Outcome

S7.3. 3.1-Investigate and demonstrate force, the effect of opposing forces on objects and demonstrate ways of minimizing these forces

Force

1. A force is a power or energy exerted (applied) that can cause an object to move faster or slower,

stop, change direction or change size or shape.

2. It cannot be seen but one can see how it affects an object.

3. Forces are;

Magnitude of Forces

1. Magnitude-is the strength/weakness of the force.

2. In diagrams, the magnitude of the force is indicated by the length of the arrow.

Low Magnitude High Magnitude

(Weak Force) (Strong Force)

-The box will slightly move or does not move at all. - The box will move.

Friction

- It is the force that opposes the motion of objects.

Types of Friction

Static Friction Sliding Friction Rolling Friction

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Advantages and Disadvantages of Friction

Advantages Disadvantages

1. Prevents us from slipping. 1. Wear and tear objects.

2. Stops a moving vehicle 2.Difficulty in moving heavy objects.

3. Keeps the position of an object on any surface. 3.Energy is wasted.

4. Holds or grips things. 4.Produces heat/ fire and noise.

5. Sharpens a knife. 5.Increase petrol consumption.

Activity

1. Illustrate the direction of a car when in motion together with its friction.

2. A weak force indicates that the object will ________________________________________.

3. Name 2 types of friction; ___________________, ___________________.

4. Give 2 advantages of friction.

_______________________________________________________________________________

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5. Give two disadvantages of friction.

_______________________________________________________________________________

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