Grade 08: Science

In this unit, 'Crop production and management', you learn to explain the steps of farming and food storage. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Crop production and management' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: explain the steps of farming and food storage. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, List the steps of growing wheat in order: preparing the soil by ploughing and levelling, sowing selected seeds, adding manure and fertiliser, irrigation, weeding, harvesting, threshing and winnowing, then storage.
2. Step 2, Calculate seed and yield. Suppose a field of 2 hectares needs 100 kg of seed per hectare, so 2 x 100 = 200 kg. If the yield is 4000 kg per hectare, the harvest is 2 x 4000 = 8000 kg, which is 40 times the seed.
3. Step 3, Compare manure and fertiliser. Manure is organic from decayed plants and animal waste and improves soil structure. Fertilisers like urea are manufactured, give nutrients quickly, but overuse pollutes water.
4. Step 4, Choose irrigation. Drip irrigation delivers water drop by drop at the roots and can cut water use a lot compared with flooding. Sprinklers suit uneven land and lawns.
5. Step 5, Explain storage. Grain must be dried to about 12 to 14 per cent moisture, kept in clean, dry bins, and protected from rats and insects, because damp grain grows fungi and spoils.
6. Step 6, Your turn: a 1.5 hectare field yields 3200 kg per hectare of rice. What is the harvest? Answer: 1.5 x 3200 = 4800 kg.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Explain the steps of farming and food storage: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Microorganisms: friend and foe', you learn to describe useful and harmful microbes. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Microorganisms: friend and foe' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: describe useful and harmful microbes. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Look at curd formation. Add 1 teaspoon of curd to 250 mL of warm milk at about 40 C and leave overnight. Lactobacillus bacteria turn milk sugar into lactic acid, so milk thickens into curd.
2. Step 2, Observe yeast. Mix 1 teaspoon of yeast and 1 teaspoon of sugar in 100 mL of warm water. After 30 minutes it froths with carbon dioxide from respiration. This makes dough rise in bread, and fermentation gives alcohol.
3. Step 3, List useful microbes: bacteria in curd and in vitamin and antibiotic production, yeast for bread and alcohol, bacteria in the soil that fix nitrogen, and bacteria that decompose waste. Penicillin comes from a mould.
4. Step 4, List harmful microbes and diseases: cholera and typhoid by contaminated water, malaria by Plasmodium through mosquitoes, tuberculosis through air, and fungi that spoil bread. Show a food chain from contamination to illness.
5. Step 5, Prevent spread: wash hands for 20 seconds with soap, boil or filter water, vaccinate, keep food covered and cold, and remove standing water where mosquitoes lay eggs. Refrigeration at about 4 C slows microbial growth.
6. Step 6, Your turn: explain why bread dough placed in a warm place rises faster than in the fridge. Answer: yeast respires faster at warm temperature, giving more carbon dioxide gas.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Describe useful and harmful microbes: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Synthetic fibres and plastics', you learn to compare natural and synthetic materials and recycling. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Synthetic fibres and plastics' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: compare natural and synthetic materials and recycling. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Compare materials. Cotton and wool are natural fibres from plants and animals. Nylon, polyester and acrylic are synthetic fibres made from petrochemicals. Nylon is strong and light, so it is used in ropes and parachutes.
2. Step 2, Teacher demonstration only, outdoors or in a ventilated space, with tongs on tiny samples; never at home. Cotton burns with a paper smell and ash. Wool smells like burning hair. Nylon melts into a bead and shrinks from the flame, showing a synthetic.
3. Step 3, Compare in a table: absorbs water (cotton yes, polyester little), dries fast (polyester yes), strength (nylon high), cost and durability. Wash a 10 cm swatch of each and note wet weights.
4. Step 4, Explain plastics. They are polymers, long chains of repeating units. Thermoplastics like polythene soften on heating and can be remoulded. Thermosetting plastics like bakelite harden permanently and are used for electrical switches.
5. Step 5, Discuss environment: plastic is non-biodegradable and can last hundreds of years. Use the R principles: refuse, reduce, reuse and recycle. Sort plastics by recycling code and send to proper collection.
6. Step 6, Your turn: which fibre would you choose for a raincoat and which for summer wear, and why? Answer: a synthetic like nylon or polyester that repels water for the raincoat; cotton for summer as it absorbs sweat.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Compare natural and synthetic materials and recycling: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Metals and non-metals', you learn to compare properties and uses. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Metals and non-metals' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: compare properties and uses. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Test properties of samples: iron, copper, aluminium, sulphur, carbon, and zinc. Metals are shiny, hard, malleable (hammer into sheets), ductile (draw into wire) and sonorous when struck. Sulphur is dull and brittle.
2. Step 2, Test conductivity with a 3 V circuit. Copper, aluminium and iron light the bulb. Sulphur does not. Graphite, a form of carbon, is a non-metal that conducts. Record exceptions: mercury is a liquid metal, graphite conducts.
3. Step 3, Teacher demonstration of reactions with oxygen; wear goggles. Burn magnesium ribbon with tongs, without looking straight at the bright white flame. It forms white magnesium oxide, which turns red litmus blue, so it is basic. Sulphur burns in a fume cupboard only; its oxide gives an acid.
4. Step 4, Write the equation: 2Mg + O2 gives 2MgO. Check atoms: 2 Mg and 2 O on each side. Conclusion: metal oxides are generally basic, non-metal oxides are generally acidic.
5. Step 5, Link uses to properties: copper for wires (ductile, conductor), aluminium foil for packing (malleable), iron for bridges (strong), sulphur for gunpowder and matches, carbon as graphite in pencils and as fuel.
6. Step 6, Your turn: a silvery solid hammers into a sheet and rings when struck. Is it a metal? Name its oxide's nature. Answer: yes, a metal; its oxide is likely basic.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Compare properties and uses: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Combustion and flame', you learn to describe fire conditions, fuels and fire safety. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Combustion and flame' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: describe fire conditions, fuels and fire safety. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Identify the three needs of combustion: a fuel, oxygen from air, and heat to reach the ignition temperature. Remove any one and the fire stops. This is the fire triangle.
2. Step 2, Show it. Light a candle and cover with an inverted glass jar. The flame goes out after a few seconds when oxygen is used. Compare with two candles under jars of 250 mL and 1 L: the larger lasts longer.
3. Step 3, Compare fuels using calorific value. LPG gives about 50 kJ per g, wood about 17 kJ per g, and hydrogen about 120 kJ per g, though sources differ a little. Burning 100 g of LPG gives about 100 x 50 = 5000 kJ.
4. Step 4, Draw the flame zones: inner dark zone with unburnt wax vapour, middle luminous zone with partial combustion, and the outer non-luminous zone with complete combustion, hottest part. A goldsmith uses the outer zone.
5. Step 5, Fire safety: water extinguishes wood and paper fires, but not oil or electric fires, where CO2 or foam extinguishers cut oxygen. Stop, drop and roll if clothes catch fire, and call the fire service.
6. Step 6, Your turn: how much heat comes from burning 200 g of wood at 17 kJ per g? Answer: 200 x 17 = 3400 kJ.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Describe fire conditions, fuels and fire safety: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Force and pressure', you learn to calculate pressure and describe friction. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Force and pressure' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: calculate pressure and describe friction. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Use P = F / A. A brick weighs 20 N. Its face areas are 0.02 m2 (large) and 0.005 m2 (small). On the large face: 20 / 0.02 = 1000 Pa. On the small face: 20 / 0.005 = 4000 Pa.
2. Step 2, Conclude: the same force on a smaller area gives more pressure. That is why a knife has a sharp edge and tractors have wide tyres. A pascal is one newton per square metre.
3. Step 3, Liquid pressure rises with depth. In a tall can with holes at 5 cm, 15 cm and 25 cm, water squirts farthest from the lowest hole. Pressure equals density x g x depth, so at 10 m in water it is 1000 x 10 x 10 = 100000 Pa extra.
4. Step 4, Atmospheric pressure at sea level is about 101,000 Pa. It pushes on a 1 m2 surface with about 101,000 N, but our bodies push back with equal internal pressure.
5. Step 5, Friction opposes sliding. Pull a 2 kg block on wood with a spring balance. Suppose it reads 6 N on wood and 3 N on polished tile. Rough surfaces have more friction. Rolling needs less force than sliding, so wheels help.
6. Step 6, Your turn: a 600 N person stands on two feet with total area 0.04 m2. Find the pressure. Answer: 600 / 0.04 = 15000 Pa.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Calculate pressure and describe friction: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Sound and light', you learn to explain reflection and the working of the eye. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Sound and light' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: explain reflection and the working of the eye. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Apply the law of reflection. Shine a narrow beam on a plane mirror so the angle of incidence is 30 degrees measured from the normal. The reflected ray leaves at 30 degrees on the other side. Incident ray, reflected ray and normal lie in one plane.
2. Step 2, Describe the image in a plane mirror: virtual, upright, same size, laterally inverted, and as far behind the mirror as the object is in front. If you stand 2 m from the mirror, your image appears 4 m from you.
3. Step 3, Use two mirrors at 90 degrees. An object at the corner gives 3 images. The number formula n = 360 / angle - 1 gives 360/90 - 1 = 3. For a 60 degree angle it gives 5.
4. Step 4, Label the eye: cornea refracts light, pupil controls entry, iris adjusts its size, lens focuses, retina holds rods for dim light and cones for colour, optic nerve carries signals to the brain. In bright light the pupil shrinks.
5. Step 5, Link sound. Sound reflects as echoes. For an echo to be heard, the surface must be at least about 17 m away, since sound at 340 m/s takes 0.1 s for a round trip of 34 m.
6. Step 6, Your turn: a ray hits a mirror at 40 degrees to the normal. Give the reflected angle and the number of images with mirrors at 72 degrees. Answer: 40 degrees; 360/72 - 1 = 4 images.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Explain reflection and the working of the eye: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Cells and reproduction', you learn to describe cell structure and reproduction in animals. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Cells and reproduction' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: describe cell structure and reproduction in animals. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Describe cell structure. A cell is the basic unit of life. Every cell has a membrane, which controls what goes in and out, cytoplasm, where reactions happen, and a nucleus, which holds the instructions (DNA). Plant cells also have a cell wall, chloroplasts and a large vacuole.
2. Step 2, Observe cells safely. Use a light microscope and a prepared slide of onion skin or cheek cells. Use a 10x eyepiece and a 40x objective: total magnification is 10 x 40 = 400 times. Safety: carry the microscope with two hands, never use the mirror to face the sun, and handle slides and stains with care.
3. Step 3, Compare animal and plant cells in a table with columns Part, Animal cell, Plant cell, Job. Membrane: yes, yes, controls entry. Nucleus: yes, yes, control centre. Cell wall: no, yes, support. Chloroplast: no, yes, makes food. Add vacuole and cytoplasm rows.
4. Step 4, Describe sexual reproduction in animals. A male sex cell (sperm) joins a female sex cell (egg) in fertilisation, forming a zygote. Each human sex cell has 23 chromosomes, so the zygote has 23 + 23 = 46, the normal number in body cells. Fish fertilise eggs outside the body, and mammals inside.
5. Step 5, Describe growth and asexual reproduction. A zygote divides by mitosis: 1 cell, then 2, 4, 8, 16, 32, doubling each time, so after 5 divisions there are 2 to the power 5 = 32 cells. Hydra reproduces asexually by budding, and amoeba splits in two, so offspring are identical.
6. Step 6, Your turn: calculate the magnification using a 10x eyepiece and a 100x objective, and say how many cells there are after 6 divisions from one cell. Answer: 1000 times; 2 to the power 6 = 64 cells.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Describe cell structure and reproduction in animals: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

In this unit, 'Chemical effects of electric current', you learn to show electrolysis and electroplating. You work with notes, a worked line and a self-mark. You see it, say it, then do it alone.

• Observe: see, touch, measure or watch a safe demonstration linked to 'Chemical effects of electric current' and write what you notice.
• Explain: use the key words of the unit to say what is happening and why, in a few lines.
• Use it: show electrolysis and electroplating. Use a diagram, table or short calculation where it fits.
• Test and conclude: say what evidence supports your answer and what you would change.

Step by step.

1. Step 1, Test conductivity of liquids with a 6 V circuit and a bulb. Distilled water: no glow. Lemon juice, salt solution and copper sulphate solution: glow. Sugar solution: no glow. Ionic solutions conduct and give chemical effects.
2. Step 2, Electrolyse copper sulphate solution with two copper plates. The cathode gains a pink-brown coating. The anode loses mass. If the cathode gains 0.40 g and the anode loses 0.40 g, mass is conserved overall.
3. Step 3, Explain: copper ions Cu2+ move to the cathode and gain electrons, forming copper atoms that deposit. Copper atoms at the anode lose electrons and enter the solution as ions. The blue colour of the solution stays the same.
4. Step 4, Electroplate an iron key with copper. Make the key the cathode and a copper strip the anode in copper sulphate. After 20 minutes at a steady current it has a thin copper layer. Cleaned objects give an even coat.
5. Step 5, Name uses: chrome plating on taps, tin plating on food cans, silver plating on cutlery, and purifying copper. Plating protects against rust and improves look.
6. Step 6, Your turn: in plating a spoon with silver, which electrode is the spoon and which is the silver strip? Answer: the spoon is the cathode, the silver strip is the anode, in a silver salt solution.

Activity. About 30 to 40 minutes of class work, then one short practice task for home. Keep evidence: a worked task and a corrected copy.

Standard to meet. Show electrolysis and electroplating: at least 8 of 10 marks on a short task, with one line of reasoning for each answer.

On the slide: L1 Basic · Using my five senses

Notes: Name the five senses and use them to describe a safe object. Notes: place a leaf, a smooth stone and a soft cloth in a bag; learners touch and describe each. Never taste or smell unknown things; teach children to ask first. Grades 1 and 2.

On the slide: L2 Awareness · Fair tests

Notes: Describe a fair test by naming what is changed, what is measured and what stays the same. Notes: plant two seed pots, one in light and one in the dark, with equal water and soil. Learners say the one changed factor, and draw both pots after a week. Grades 3 and 4.

On the slide: L3 Foundation · Measuring and recording

Notes: Measure length, mass, time and temperature and record them in a table. Notes: a plant grows 2 cm in 4 days, which is 0.5 cm a day. Learners take three readings of 12, 14 and 13 mm, find the mean of 13, and say why repeats help. Grades 5 and 6.

This course: Grade 08 Science is at this level. Its units include Crop production and management; Microorganisms: friend and foe; Synthetic fibres and plastics; Metals and non-metals and more.

On the slide: L4 Practitioner · Variables, graphs and density

Notes: Apply a formula and draw a graph from a fair test. Notes: density equals mass over volume; a metal block of 54 g and 20 cm3 has density 2.7 g/cm3. Learners plot mass against volume for three blocks and read the gradient. Dry the benchtop before using water. Grades 7 and 8.

On the slide: L5 Specialist · Evidence, anomalies and models

Notes: Analyse data, spot an anomaly and judge how well a model fits the evidence. Notes: readings of 5.1, 5.3, 5.2 and 7.9 hold one anomaly at 7.9, so the mean of the rest is 5.2. Learners suggest a cause, repeat the trial and write a conclusion that cites the numbers. Grades 9 and 10.

On the slide: L6 Advanced · Modelling and curve fitting

Notes: Apply least-squares fitting and error reasoning to link data to a model. Notes: the points (1,2.1), (2,3.9), (3,6.2), (4,7.8), (5,10.1) give slope 1.99 and intercept 0.05, with R squared 0.997. Learners explain what the intercept means and whether a straight line is right.

On the slide: L7 Super expert · Study design and sample size

Notes: Evaluate and create a study with a clear hypothesis, controls, sample size and ethics approval. Notes: to detect a 5-unit difference with spread 10 at 5 per cent significance and 80 per cent power needs about 63 per group. Learners write a pre-registered plan and list the risks and consent steps.