Biology Spec points covered Starter options Practical activity Teacher-led activity CB1a Microscopes B1.3 B1.4 B1.5 B1.6 Explain how changes in microscope technology, including electron microscopy, have enabled us to see cells with more clarity and detail than in the past Demonstrate an understanding of size and scale in relation to microscopy, including magnification calculations. Demonstrate an understanding of the relationship between quantitative units, including (a) milli (10-3), micro nano (10-9), pico (10-12) (b) calculations with numbers written in standard form Produce labelled scientific drawings from observations of biological specimens using microscopes 1) Ask students how microscopes work, and establish the idea that they magnify small things, making them and their details easier to see. Explain that the study of cells would not be possible without the invention of the microscope and ask students to suggest why. 2) Write the words kilo-, milli-, micro-, nano- and pico- on the board, in random order. Write the prefixes in size order on the board and then show how the units are related (kilo- multiplies the base unit by 1000, milli- divides it by one thousand, micro- divides it by 100 000 etc.). Students use microscopes to examine pre-prepared slides of small objects (e.g. hair, pollen). Students will produce a range of drawings annotated with names of objects and calculated magnifications. Equipment: Microscope, selection of pre-prepared slides (e.g. hair, pollen, fish scales, synthetic fibres, mushroom gills, ear wax, pond water, newsprint). Help students to understand the difference between resolution and magnification by using the idea of digital cameras. Those with many megapixels have a higher resolution than those with only a few. Digital resource: Size and scale animation CB1b Plant and animal cells B1.1 Explain how the sub-cellular structures of eukaryotic and prokaryotic cells are related 1) Ask students to write a simple definition of a cell. Ask for a volunteer Use a microscope to look at simple animal and/or plant cells and identify their Hold up a metre rule and ask students to estimate the width,
Digital: Inside a cell video CB1c Cell Specialisation B1.1 B1.4 B1.6 Explain how the sub-cellular structures of eukaryotic and prokaryotic cells are related to their functions, including: (a) animal cells - nucleus, cell membrane, mitochondria and ribosomes (b) plant cells - nucleus, cell membrane, cell wall, chloroplasts, mitochondria and ribosomes ... Demonstrate an understanding of size and scale in relation to microscopy, including magnification calculations Produce labelled scientific drawings from observations of biological specimens using microscopes 1) Write the word 'adaptation' on the board. Write down adaptations of three animal species. Reinforce the link between adaptation and environment to show the purpose of the adaptation. Explain that different kinds of cell have different forms and different functions. This leads to the idea that the form of different kinds of cells is adapted to their function. 2) Challenge students to sketch the main features of different kinds of cells that have different functions related to cell structures with which they are familiar. Students should annotate their sketches to identify the features that are adaptations to their Students study prepared slides of some specialised human cells. Students identify adaptations within the cells. Equipment: Prepared and labelled slides of human cells and tissues (Suitable slides include: human sperm cells, human egg cell, ciliated cells lining the oviduct, microvillar epithelial tissue of small intestine.); light microscope and light source, transparent ruler or graticule. Work with student to think up a simple mnemonic that will help with remembering the difference between haploid and diploid, such as HAploid cells have HAlf the normal chromosome number. Using two sizes of sieve with the same mesh to show how quickly the same amount of powder (e.g. flour) can be sieved through it. Make the link between surface area and rate of absorption. Digital: To follow
function. CB1d Inside Bacteria B1.1 B1.5 Explain how the sub-cellular structures of eukaryotic and prokaryotic cells are related to their functions, including: ... (c) bacteria - chromosomal DNA, plasmid DNA, cell membrane, ribosomes and flagella. Demonstrate an understanding of the relationship between quantitative units, including (a) milli (10-3), micro nano (10-9), pico (10-12) 1) Write the word ‘bacteria’ on the board. Discuss with students the sub-cellular structures that they would expect to find in bacterial cells. 2) Remind students that both plant and animal cells are described as being eukaryotic because they have nuclei. Establish the idea that eukaryotic cells contain nuclei but prokaryotic cells do not. Students examine live yoghurt cultures to look for bacteria. Even at the highest magnifications, bacteria will appear very small. Students should draw outlines of any bacteria they can see. Equipment: Live yoghurt (liquid varieties are more useful), sterile toothpicks/cocktail sticks, access to beaker of 1% Virkon in which to dispose of used toothpicks, light microscope, microscope slide, coverslip, water or methylene blue stain, paper towel, gloves, pipette. Optional: microscope with ×100 oil-immersion objective, video camera and display, non-live yoghurts. Write up A × 10n on the board and explain how standard form works. Use arrows to illustrate how the unit moves by the number of times shown by the power of ten, both to the left and right for positive and negative powers. Digital resource: Cell parts and functions interactive B1e Enzymes and nutrition B1.12 Explain the importance of enzymes as biological catalysts in the synthesis of carbohydrates, proteins and lipids and their breakdown 1) Show students a piece of fruit that has started to go soft due to decay by a mould fungus. Explain that the fungus is Students investigate the action on starch solution of amylase from their own saliva or with prepared amylase solution, using the iodine test. Demonstrate to students how starch can be synthesised from a potato.
Optional: if using saliva – hypochlorite (bleach) solution or 1% Virkon solution for disinfection of equipment and benches, small beaker or other container for collecting saliva. biological molecule (each cloth should have the same range of stains, and there should be one cloth for each type of enzyme to be used), range of enzymes that have different substrates Digital resource: Enzymes animation B1g Enzymes activity B1.9 B1.11 B1.10 Explain the effects of temperature, substrate concentration and pH on enzyme activity Demonstrate an understanding of rate calculations for enzyme activity Investigate the factors that affect enzyme activity 1) Cut an apple or pear in half (slices of celeriac also work well), and sprinkle lemon juice over the cut surface of one half. Explain that cutting the fruit breaks open cells, releasing enzymes that were inside. Ask students to describe the changes they see happening, and try to suggest a reason for any differences between the two halves 2) Ask how you would tell from the results of two experiments using This practical investigates the effect of pH on amylase, the enzyme that catalyses the breakdown of starch to smaller sugar molecules. The iodine test identifies the presence of starch, but does not react with sugar molecules The optimum pH for human salivary amylase is pH7. Other amylases may vary from this value, but there should be one pH that clearly allows greater enzyme activity than the others. Equipment: For each pH tested: test tube containing 5 Use a suitable enzyme and substrate such as using catalase/hydrogen peroxide and measure the volume of oxygen collected every 30 s for 5 minutes. Measure and record the pH of the enzyme/substrate solution at the start of the experiment.Record the cumulative gas volume over time, and plot the values on a graph of gas volume against time Students should make the link between the
starch and amylase which had the faster rate. Students consider what they would need to know in order to calculate the rate of the reaction. cm3 freshly made 1% starch suspension (mix 5 g soluble starch with a little cold water, pour into 500 cm3 of boiling water and stir well, then boil until you have a clear solution), test tube containing 1 cm3 1% amylase solution (or 0.5% pancreatin solution) or saliva collected by student, water bath at optimum temperature for the enzyme (e.g. 37 °C), buffer solution at a set pH (see table above), 5 cm3 syringe or pipette, beaker of water for washing pipette, eye protection, 0.01 mol dm-3 iodine solution, well tray (spotting tile). Optional: if using saliva – hypochlorite (bleach) solution or 1% Virkon solution for disinfection of equipment and benches, small beaker or other container for collecting saliva. rate of reaction slowing down and the amount of substrate left in the solution decreasing. Equipment: hydrogen peroxide solution (using one of following concentrations: 10, 15, 20, 25, 30 vol) in clean brown bottle, 2-holed bung with delivery tube in one hole connected to rubber tubing, conical flask, large syringe (at least 20 cm3), trough containing water, 2 cm3 syringe, 50 cm3 or 100 cm3 measuring cylinder, clamp stand and boss, stopclock or stopwatch, eye protection. Digital: Substrate concentration presentation B1h Transporting substances B1.15 Explain how substances are transported by diffusion, osmosis and active transport. Show students the diffusion of potassium manganate(VII) in water Students measures the percentage change in mass of strips of potato placed in Demonstrate diffusion and osmosis in the small intestine using a
B1.17 B1.16 Calculate percentage gain and loss of mass in osmosis Investigate osmosis in potatoes by placing a crystal at the bottom of a large beaker of water. Ask students to work in pairs to discuss why the colour disperses through the water. Ask where in the water the manganate is most concentrated at the start, and how concentration of manganate at any particular point in the water changes over time. Use this to lead to a definition of diffusion, as the overall movement of particles from where there are more of them (higher concentration) to where there are fewer (a lower concentration). Equipment: Large beaker of water, potassium manganate(VII) crystal, tongs – alternatively video of diffusion of potassium manganate(VII) in water. different concentrations of solution. Using a coloured sugar syrup, such as blackcurrant squash, makes it easier for students to see that the solutions are of different concentrations. Students should find that the potato strip in pure water gains mass, while the rest lose mass in relation to how much water was in the solution (i.e. the potato in the solution with least water [100% solution] loses most mass). Equipment: Per group: 4 potato strips of identical size, accurate balance, 4 boiling tubes and rack (or beakers), waterproof pen, 4 labelled solutions containing different amounts of water, forceps, paper towels. Visking tubing bag. Explain to students that glucose and water molecules are small enough to cross the membrane, but that starch molecules are not. Ask students to work in pairs and use that information to help them predict whether diffusion and osmosis will occur over that time, and in which direction. Digital: Osmosis animation
Chemistry Spec points covered Starter options Practical activity Teacher-led activity C1a States of matter C2.1 C2.2 C2.3 C2.4 Describe the arrangement, movement and the relative energy of particles in each of the three states of matter: solid, liquid and gas Recall the names used for the interconversions between the three states of matter, recognising that these are physical changes Explain the changes in arrangement, movement and energy of particles during these interconversions Predict the physical state of a substance under specified conditions, given suitable data (links to a Maths statement). In pairs, using paper or mini-whiteboards, students draw and write what they already know about the particles in the three states of matter. Groups feedback one or more of their answers to the class. Students record the temperature and appearance of a molten test substance. The temperature should decrease rapidly until the substance begins to solidify, at which point the temperature should remain constant. When the substance has solidified, its temperature should begin to decrease again. Equipment: Eye protection, stop clock, test tube rack. Boiling tube containing the molten test substance with a thermometer. Demonstrate the sublimation and deposition of iodine. Boiling water is not hot enough to melt or boil the iodine, so why does a vapour form and crystals re-form? Discuss the changes in arrangement, closeness and movement of the particles in the two state changes. Equipment Eye protection, iodine (maximum 0.25 g), stand, boss, clamp, round-bottomed flask, boiling tube, crushed ice, mineral wool, large beaker, kettle for hot water. Digital Changes of state animation
C2a Mixtures C3.1 C3.2 Explain the differences between a pure substance and a mixture Interpret melting point data to distinguish between pure substances which have a sharp melting point and mixtures which melt over a range of temperatures 1) Begin by displaying a scanning tunnelling electron microscope image of some atoms as students come in. Challenge students to write one sentence indicating whether they think the image shows a pure substance or a mixture, and explaining how they can tell. 2) Ask students to match four materials (diamond, nitrogen, ice and gold) with their melting points in °C (3550, -210, 0, 1063). Students record the melting temperature of ice over time and compare this with the melting temperature of an mixture. Students should observe that the temperature of pure ice does not change as the ice is melting, but the temperature of the impure ice does. Equipment: 250 cm3 beaker, 5 ice cubes, 100 g salt (NaCl), thermometer or thermocouple (ideally with a lower range to −20°C), stop clock, mass balance Ensure that students fully understand the differences between pure substances and mixtures before moving on to look at their melting points. Discuss with the class what happens to the physical arrangement of particles during melting. A reasonable focus might be the ordering of particles and their separation. Digital: Pure substances and mixtures video C2b Filtration and crystalisation C3.3 C0.6 Explain the experimental techniques for separation of mixtures by ... c filtration d crystallisation ... Evaluate the risks in a practical procedure and suggest suitable 1) Hold up pieces of apparatus and ask what each one is. Ask students to explain or show how they would draw each one as part of a diagram. 2) Find some examples of pictures illustrating filtration on the internet. The aim of the investigation is to identify which of three samples of rock salt contains the largest quantity of salt. Students should submit their plan for approval before carrying it out. Equipment: Should include: conical flask (250 cm3), filter Demonstrate how to heat to dryness safely. Use the demonstration to compare the crystal sizes produced when forming crystals quickly using a Bunsen burner, and those produced by slow evaporation. To
precautions for a range of practicals including those mentioned in the specification Pictures could include filter feeders, chemical filtration equipment and vacuum filters. Challenge students to spot the link between the photos. paper, filter funnel, beaker, stirring rod, distilled water, mortar and pestle, mass balance, rock salt, Bunsen burner, tripod, evaporating basin, gauze, tongs. Note only one source of rock salt is required (although if supplies from different locations are available they may be used). If only one source of rock salt is available grit may be added to the source material in different amounts, creating a range of start rock salt materials. demonstrate crystals that have formed very slowly you could use a pre-prepared sample that has been left out to evaporate Digital: Sea salt production video C2c Paper chromatography C3.3 C3.5 Explain the experimental techniques for separation of mixtures by ... e paper chromatography Describe paper chromatography as the separation of mixtures of soluble substances by running a solvent (mobile phase) through the mixture on the paper (the paper contains the stationary phase), which causes the substances to move 1) Show a chromatogram to the students and ask them for keywords to help describe how this has been created. Equipment: chromatogram (made using filter paper, scissors, small beaker, water, coloured sweet/ink/food colouring) 2) Show the students a short video clip about the Using a crime scenario students test different pens to see if one of them could have been used to write a 'poison pen' letter and compare against a chromatogram supposedly made from ink extracted from the letter. Equipment: 250 ml beaker, chromatography paper cut to fit beaker and stapled to a splint or attached to a pencil or glass rod using paper clips, four different black felt pens or Demonstrate to students how to use chromatography to analyse mixtures of amino acids. Equipment: samples of individual amino acids; mixture of the individual samples; chromatography paper; sticky tape; pencil; melting point tubes (1 for each sample); beaker with lid (large
C2.6 C3.7 at different rates over the paper Interpret a paper chromatogram a to distinguish between pure and impure substances b to identify substances by comparison with known substances c to identify substances by calculation and the use of rf values (links to a Maths statement). Investigate the composition of inks using simple … paper chromatography use of chromatography in identifying a forgery (search for ‘CSI chromatography’ on the internet) water-soluble marker pens, labelled A to D. Selection of four or more pens of one colour (blue or black) with different combinations of dyes in the ink, labelled Suspect 1, Suspect 2 etc; pre-prepared chromatogram made using one of the pens, using the same paper that students will use; suitable solvent (see above) if the pens to be tested have permanent inks. NB The practical can be run without the ‘poison pen’ scenario enough to hold rolled chromatography paper); solvent (mixture of butan-1-ol, ethanoic acid and water in the ratio 4:1:2 by volume), ninhyrdin spray (2% ninhydrin in butan-1-ol), eye protection, access to fume cupboard, chromatogram, chromatogram sprayed with ninhydrin and baked. Digital: to follow C2d Distillation C3.3 C0.6 Explain the experimental techniques for separation of mixtures by a simple distillation b fractional distillation (links to a Maths statement). Evaluate the risks in a practical procedure and suggest suitable To follow To follow To follow
solution, 2 × beakers. Washing up bowl, beaker, cling film, small weight, salty water. Digital: Water treatment interactive C3a Atomic structure C1.1 C1.2 C1.3 C1.4 Describe how the Dalton model of an atom has changed because of the discovery of subatomic particles Describe the structure of an atom as a nucleus containing protons and neutrons, surrounded by electrons in shells Recall the relative charge and relative mass of (links to a Maths statement). a a proton b a neutron c an electron Explain why atoms contain equal numbers of protons and electrons (links to a Maths statement). Write the word ‘atoms’ in the centre of the board, then write the words 'matter’, ‘elements’, ‘compounds’, ‘particles’, ‘structure’ and ‘John Dalton’, around them in a rough circle. Ask students to write down as many links as they can between the term ‘atoms’ and the words around it. Ask students to use a variety of resources to make an atomic model. The model should be three-dimensional and show the arrangement of the subatomic particles. Each group of students should be asked to produce models of a specific element. Students produce a range of models representing the nuclear atom and use it to describe how Dalton’s atomic model has changed. The following ideas should be highlighted to students: The mass and charge of the subatomic particles are too small for everyday use, so we use relative masses and charges. The nucleus of an atom is very small relative to the atom, which is mostly empty space. Digital: Inside the atom animation
C1.5 Describe the nucleus of an atom as very small compared to the overall size of the atom C3b Atomic mass and numbers C1.6 C1.7 C1.8 Recall that most of the mass of an atom is concentrated in the nucleus Recall the meaning of the term mass number of an atom (links to a Maths statement). Describe atoms of a given element as having the same number of protons in the nucleus and that this number is unique to that element Calculate the numbers of protons, neutrons and electrons in atoms given the atomic number and mass number (links to a Maths statement). 1) Students brainstorm everything they know about ‘elements and the periodic table’ 2) Challenge students to think up ways of telling different atoms apart. Students weigh samples, of different elements, made up so the masses of the samples will be in the same proportions as the masses of the atoms. Students then use the data, for carbon and magnesium, to work out the ratios of the mass numbers, and the masses of samples, in their simplest form. Students should conclude that the ratios of the mass numbers of the atoms of elements are the same as the ratios of the masses of their atoms. Equipment: electronic balance (at least accurate to +/- 0.1 g), labelled containers, with sealed lids, containing samples of four elements: carbon (4.5g), magnesium (9g), sulfur (12g) and copper (24g) Display the nuclide notation (AZSymbol) for some simple atoms on the board, and initiate a class discussion on how models of the nuclei of these atoms could be made. Demonstrate how the nuclei of some of the atoms described on the board can be constructed using polystyrene balls of different colours (e.g. red for protons and green for neutrons) and adhesive putty. Equipment: coloured polystyrene balls and adhesive putty and some prepared nuclei. Digital: Protons, neutrons and electrons interactive activity 0
C3c Isotopes C1.9 Describe isotopes as different atoms of the same element containing the same number of protons but different numbers of neutrons in their nuclei Calculate the numbers of protons, neutrons and electrons in atoms given the atomic number and mass number (links to a Maths statement). Explain how the existence of isotopes results in some relative atomic masses of some elements not being whole numbers Calculate the relative atomic mass of an element from the relative masses and abundances of its isotopes (links to a Maths statement). 1) Write the following terms on the board: element, atom, nucleus, protons, neutrons, electrons and electron shells. Ask students to work in pairs to write one sentence that contains all the terms. 2) Show the students five boxes, labelled with different masses, in easy whole numbers. E.g. box A = 2 kg; box B = 4 kg; box C = 6 kg; box D = 10 kg and box E = 15 kg. Discuss the idea of relative amounts with students and how we can calculate how much greater or smaller one thing is compared with another. Give students six boxes containing a set number of heavy gauge washers (e.g. 1 box containing 2 washers, 3 boxes containing 4 washers and 2 boxes containing 6 washers). Tell students the mass of the empty boxes. Working in groups, students measure the masses of the boxes and work out the mass of their contents. Students then carry out calculations on the relative masses of the contents of the boxes. Equipment: (per group) electronic balance, 6 opaque boxes, which are sealed but can be opened, each containing a set number of heavy gauge washers (e.g. 1 box containing 2 washers, 3 boxes containing 4 washers and 2 boxes containing 6 washers Using polystyrene balls and sticky pads demonstrate the structure of the nuclei of different isotopes of lithium (6Li and 7Li). Using a balance demonstrate to the students that isotopes of the same element have different masses. (Discuss why electrons are removed/omitted from the models) Define the term ‘isotope’ and discuss why they are still atoms of the same element. Digital: to follow
is ideal, the longer the better); small metal block (or other suitable object to make a sound in the solid); 2 'stethoscope' sound sensors (such as those available from Data Harvest)/microphones, capable of detecting sound in solids; datalogger. Optional: pedometer; smartphone with speed measuring app; GPS. bottom is the average speed. Equipment: Ramp; books or other objects to prop up end of ramp; 2 light gates and data logger; trolley with card fixed vertically on top; block of wood and G-clamp. Digital: Motion graphs animation P1c Acceleration P1.6 P1.7 Recall and use the equation: acceleration (metre per second squared, m/s2) = change in velocity (metre per second, m/s) / time taken (second, s) a = (v-u)/t Use the equation: (final velocity )2 ((metre/second)2, (m/s)2 – (initial velocity)2((metre/second)2, (m/s)2) = 2 × acceleration (metre per second squared, Ask students to work in groups to think about how you work out different quantities that describe motion and the units they are measured in. Draw up a table with headings ‘Quantity’, ‘Unit’, ‘How to work it out’, and ‘Is it a vector?’. Give one of the quantities ‘speed’, ‘velocity’, ‘acceleration’, ‘displacement’ and ‘distance’ to each group. Students use light gates to measure the acceleration of a card in free fall. Students should obtain a result of approximately 10 m/s2. Equipment: two light gates (e.g PASCO Smart Timer Photogate System ME-8932); data logger; 10 cm long piece of card weighted with metre rule; clamps and stand. Show students step by step how to use the formulas, including the meaning of negative values for acceleration. Digital: Acceleration calculations presentation
P1.11 m/s2) × distance (metre, m) v2 – u2 = 2 × a × x Recall that the acceleration, g, in free fall is 10 m/s2 and be able to estimate the magnitudes of everyday accelerations They write down how each is measured or calculated and its units and decide if it is a vector and why. Optional: strobe light; video camera/digital camera; golf ball; metre rule. P1d Velocity/time graphs P1.8 Analyse velocity/time graphs to: a compare acceleration from gradients qualitatively b calculate the acceleration from the gradient (for uniform acceleration only) c determine the distance travelled using the area between the graph line and the time axis (for uniform acceleration only) On the board sketch two distance/time graphs, one with a horizontal line and one with the line sloping upwards. Label the axes of each, and ask the class what these show (staying still, moving at a steady speed). Now change the label on the vertical axis to read ‘Velocity’. Ask what the horizontal line now shows. Elicit that this means moving in a particular direction at a steady speed. Ask what the sloping line now shows. Elicit that this Students use ticker timers and tape to produce velocity/time graphs for a trolley accelerating down a ramp for two different slopes. Equipment: runway and support, e.g. wood blocks (the wooden board should be about 1.0–1.5 m long); dynamics trolley (check that wheels are free running); ticker-timer and power supply (check tape is under carbon disc if this method is used); ticker-tape (lengths of about 2 m or other length consistent with length of runway. Students can share Explain why the gradient and area under a velocity/time graph give the acceleration and distance respectively Digital: Calculations from graphs presentation
shows a steadily increasing velocity – acceleration. runways); sticky tape; scissors; plain paper; rulers P2a Resultant forces P1.12 Recall Newton’s first law and use it in the following situations: a where the resultant force on a body is zero i.e. the body is moving at a constant velocity or is at rest b where the resultant force is not zero i.e. the speed and/or direction of the body changes 1) Students work in groups to write down five things they remember about forces and their effects. 2) Have ready a large beaker of water and a foam or soft ball that will float.Hold the ball in your hand. Float the ball in the water. Ask for volunteers to come to the front of the class and make a sketch of the ball with force arrows (equal and opposite). Students investigate forces acting on objects.. Equipment: wooden block with hook for force meter; large sheet of sandpaper; masses (sufficient to give different readings on force meter when the block is dragged along different surfaces); force meter; string; large beaker of water; two objects small enough to fit in beaker, one of which should float and one sink Find images of objects stationary and in motion on the internet or in books. Show them to students, and ask students to describe the types of forces acting on the objects and the directions in which they are acting. Digital: Different forces presentation P2b Newton’s First law P1.12 Recall Newton’s first law and use it in the following situations: a where the resultant force on a body is zero i.e. the body is moving at a constant velocity or is at rest b where the resultant force is not zero i.e. the speed and/or 1) Fill a balloon with helium and tether it to a weight. Ask students to work in pairs to describe the forces on the balloon while it is tethered, and to describe what would happen if the balloon is released from the weight. Students work together in groups of to apply multiple forces to a block, work out the resultant and predict its effect on the movement of the block. Students should determine that when the total force on each side is equal, the resultant is Set up a glider on an air track with elastic bands at both ends. Show students the apparatus without the air on and ask them to predict what will happen if you push a glider. Then explain
work in pairs or small groups to write down two statements about mass and weight that are true, and one that is false. forcemeter (range suitable for weighing all the supplied masses). with a total thrust of approximately 16 000 N. Ask students to think of as many reasons as they can why the two spacecraft are so different. Digital: Leaving the Earth video P2d Acceleration (Newton’s Second law) P1.13 P1.18 P1.15 Recall and use Newton's second law as force (newton, N) = mass (kilogram, kg) × acceleration (metre per second squared, m/s2) F = m × a Explain that inertial mass is a measure of how difficult it is to change the velocity of an object (including from rest) and know that it is defined as the ratio of force over acceleration. Investigate the relationship between force, mass and Demonstrate in front of students that a heavy object falls faster than something light with greater air resistance, such as a feather. Ask for students to suggest reasons why they fall at different rates. Show a clip of the astronaut Dave Scott showing that a hammer and a feather fell at the same rate on the Moon (or . Bring out the idea that although the Students use light gates to investigate the effect of mass on the acceleration of a trolley Students should find that the acceleration is inversely proportional to mass (encourage students to plot acceleration against 1/mass to check for inverse proportionality). Students investigating the effects of force should find that acceleration is proportional to force if a fixed total mass is used. Use an airtrack setup, two gliders and some repelling magnets to demonstrate F = m × a and also to recap on action and reaction forces. Using the simple mass ratio of 2 :1, the glider with twice the mass flies off with half the speed of the lighter one. Equipment: airtrack and blower; 2 gliders; 2
acceleration downwards force is greater on a more massive object, that object also needs a greater force to give it a certain acceleration. If sufficient light gates are not available, students should mark a measured length on the ramp and use a stop clock to time how long the trolley takes to travel this distance. The acceleration can then be calculated using a = (v – u) / t Equipment: ramp and blocks; pulley and string; stacking masses and hangar; sticky tape; card; Blu-tack® or Plasticine®; 2 light gates; 2 clamps and stands; access to balance; data logger (set up to measure velocities from the light gate readings and the time between the two readings - students will need to enter the length of the card mounted on their trolley); box of crumpled newspaper. pieces of card 5.0 cm wide; pair of disc magnets; 2 light gates; thread and sticky tape; 10 g masses and (add masses and Blu-tack® to one glider to make its mass twice that of the other); means of recording times through light gates, e.g. a millisecond timer or datalogger plus software (e.g. the PASCO smart photogate timer system); matches P2e Newton’s Third law P1.19 P1.19 Recall and apply Newton's third law to equilibrium situations. [Apply Newton's third law] Set up a spring in a clamp and stand with mass hanging on the end. Discuss the forces on the mass (weight and the Students use forcemeters adjusted for horizontal use, some lengths of string and a mass hanger suspended over a pulley to investigate forces on Find images of equilibrium situations from the internet, and ask students to identify the forces. Elicit
P1.21 as: force (newton, N) = change in momentum (kilogram meter per second, kg m/s) / time (second, s) F = (mv – mu)/t Repeat the process using changes in velocity. Students should conclude that the behaviour of objects after a collision is linked to both mass and velocity. Equipment: Air track; air supply/pump; 2 gliders. conserved in these collisions. Equipment: runway; balance; trolley masses; 2 light gates with timers; 2 trolleys that join on collision (magnets, Velcro®). to show that F × t = (mv – mu), and as F × t is the same for both objects, then the change in momentum must be the same for both. Digital: Momentum and Collisions animation P2g Stopping distances P1.22 P1.23 P1.24 Explain methods of measuring human reaction times and recall typical results Recall that the stopping distance of a vehicle is made up of the sum of the thinking distance and the braking distance. Explain that the stopping distance of a vehicle is affected by a range of factors including: a) the mass of the vehicle b) the speed of the vehicle c) the driver's reaction time d) the state of the vehicle's 1) Display the Highway Code’s chart of increasing stopping distances with speed. Ask students to write down what they think braking distance and thinking distance might be and how each changes with the speed. 2) Pose a set of questions on speed limits for students to discuss in groups. Students test reaction times. Visual reaction times should be of the order of about 0.2 seconds. Equipment: Dropped ruler method: metre ruler; Circuit method: Single pole double throw (SPDT) switch (or push button switch with long leads); push button switch; digital timer (with external circuit connections); light bulb and holder; battery or power pack; connecting wires. Look at the Highway Code stopping distance chart in more detail. Students should recall that the stopping distance does not increase linearly with speed. You may also wish to discuss the fact that speed limits are not set only on the basis of stopping distances, but also because pedestrians are far more likely to survive
P1.25 brakes e) the state of the road f) the amount of friction between the tyre and the road surface. Describe the factors affecting a driver’s reaction time including drugs and distractions low-speed than impacts. Digital: Stopping distances interactive P2i Crash Hazards P1.26 P1.26 Explain the dangers caused by large decelerations… estimate the forces involved [in large decelerations] in typical situations on a public road. 1) Ask students to suggest different causes of crashes. Ask them to then think about what determines the amount of damage and what safety features are built into cars to mitigate dangers to people. 2) Show students a video on the internet showing the landing of the Mars Pathfinder probe or the Spirit and Opportunity landers. These missions used airbags to cushion the final descent of the probe. Ask students to try to explain how the Students test different designs of crumple zone on a dynamics trolley. The deformation of a piece of Blu-tack® can be used to indicate relative force. However, much better quantitative data will be obtained if a force sensor is used. Alternatively, a smartphone that includes an accelerometer can be used. Students should find that the presence of some kind of crumple zone affects the impact force. Show students two statements and discuss which of the two statements is correct: ● If two vehicles, both travelling at 60 mph, collide head-on, the crash is much worse than a car travelling at 60 mph hitting a wall. ● It's only worse because there are two lots of people to be injured and two cars to be damaged. The forces on the car are just the same. This question addresses a common