B4C4P4 Revision

1. B4C4P4 Revision

2. B4 - Homeostasis • What happens if you fall into a snow drift? • Bodies have Receptors which detect changes which inform Processing Centres which inform Effectors which cause change to keep the body constant. • The body needs Enzymes to help reactions happen at the required speed.

3. Enzymes work best at their Optimum Temperature and pH. Maintaining a Constant Temperature – shivering, sweating, goose bumps, vaso-constriction, vaso-dialtion

4. Diffusion and Osmosis • Diffusion – particles spread out • Osmosis – works when particles are dissolved in water and there is a membrane involved. Water particles move from the most concentrated side of the membrane to the least concentrated to try to even up the concentration:- What will happen here....?

5. Osmosis continued • Water can move through cell membranes from the dilute outside to the salty, concentrated inside:- But cells can also use Active Transport to get needed molecules, against the diffusion gradient...

6. Kidney Function

7. Controlling Water Balance in the body • Excess sweating, drugs like caffeine making you urinate more, eating salty food can all affect the amount you urinate. • If you are doing Higher Tier, you need to know about the control system for water balance, a negative feedback system.

8. Extreme Temperatures • If you get too hot because your body cannot lose heat fast enough you get heat stroke. Treatments include sponging with water and using a fan to reduce the body’s temperature. • If you get too cold (if core body temperature falls below 35 deg C, you get Hypothermia. Treatments include warm drinks and insulating the patient.

9. C4 – Chemical Patterns • The Periodic Table was written by a Russian Chemist, Mendeleev and contains patterns. Elements are arrange in columns called groups where each element in a group has similar properties. • Each row is called a period • Over ¾ of all elements are metals and they are on the left of the periodic table.

10. Group 1 – The Alkali Metals • All react with water – fizz. Get more reactive as you go DOWN the group and some of the lower ones like Potassium actually catch fire when reacted with water! • Lithium+WaterLithium Hydroxide+Hydrogen • The Alkali metals are soft. • The Alkali Metals react well with Group 7 elements, the Halogens (see why later on)

11. Balancing Equations (1) • Step 1 – write reaction in words:- Sodium + Chlorine  Sodium Chloride • Step 2 – write down all formulae:- Na + Cl2 NaCl (Cl always comes in pairs) • Step 3 – Balance the equation:- 2Na + Cl2 2NaCl • Step 4 – Write state symbols:- 2Na(s) + Cl2(g) 2NaCl (s)

12. Balancing Equations (2) • Step 1 – write reaction in words:- Sodium + Oxygen  Sodium Oxide • Step 2 – write down all formulae:- Na + O2 Na2O • Step 3 – Balance the equation:- 4Na + O2 2Na2O • Step 4 – Write state symbols:- 4Na(s) + O2(g) 2Na2O (s)

13. The Halogens • Group 7 elements – mostly coloured gases. • Get LESS reactive as you go DOWN the group. • Iodine can be used as an antispetic. • React well with Group 1 (alkali metals) to make useful compounds, e.g. Sodium Chloride, table salt. • They are molecular so always appear in pairs when alone, e.g. Cl2

14. Spectroscopy • An element is burned and light from its flame is viewed and, rather than see a normal spectrum you see a series of spectral lines. Each element produces its own lines so it each one can be identified. It was in this way that scientists found that the Sun must be made of Hydrogen, without ever having visited it – they just looked at the light being received and compared it to the ones they had made in the lab and saw that the Sun must consist mainly of Hydrogen. But they also found a new element – Helium – which had never been seen on Earth before.

15. Structure of the Atom • An atom is mostly a lot of space with a few tiny particles!

16. Electron Configuration • Electrons are arranged in shells around the nucleus. The first shell can take 2 electrons. The next shells can take 8. The Atomic Number of Aluminium is 13 so it has 2,8,3 electrons as in the picture:-

17. Electron Configurations and the Periodic Table Look at this little bit of the periodic table. • All elements in Period TWO have TWO of their shells filled (or part-filled) with electrons. • All elements in Group ONE have ONE electron in their outer shells.

18. Salts • There are thousands of salts. A salt is a compound made from the reaction between a metal and a non-metal. An example is Sodium Chloride, table salt. • When you melt salts or dissolve them in water, they conduct electricity as their ions are free to move (see next page)

19. Ionic Theory • When atoms form bonds they turn into IONS. An ion is a charged particle (either positive or negative). A positive ion attracts a negative ion to form a strong chemical bond. Sodium Chloride – salt crystals are hard because they have strong bonds between all the positive and negative ions.

20. How do ions form? • When they react, electrons move from one atom to another SO THAT BOTH ATOMS END UP WITH A FULL OUTER SHELL OF ELECTRONS. Electrons are NEGATIVELY CHARGED so when they move the atoms become charged particles called ions. Sodium has one electron in its outer shell whilst Chlorine has seven. Sodium’s spare electron leaves (so Sodium’s next shell down is now the complete outer shell) and goes to Chlorine to make a full outer shell of 8 electrons. The Chlorine has gained one negative electron so is now a negative ion. Because the Sodium has lost a negative electron it is now a positive ion. The positive and negative ions now attract each other to form a chemical bond. Some atoms may need to lose or gain 2 or 3 electrons to do this so will become 2+ or 2- or 3+ or 3- ions.

21. P4 - Motion • Most forces are contact forces such as Push and Pull. • Some forces such as Gravity and Magnetism act at a distance. In a rocket or jet aircraft, hot gases exit at high speed pushing the craft in the opposite direction. In a car, the wheels turn and friction makes them go forward. If the car is on ice there is no friction so it cannot move, no matter how much the wheels spin!

22. Friction • Caused by rough surfaces that stick together. To move two objects you need to break all the sticking points. Oils reduce friction because they keep the two surfaces apart.

23. Reaction Forces • When you push on a table, it bends slightly and pushes back with the same force (unless you push hard enough to break it!). The push-back force is called the Reaction Force. Your chair is pushing up with a Reaction Force that exactly matches your weight otherwise you would be falling to the floor or shooting up into the air!

24. Resultant Forces • When many forces act on an object you can simply add them to get the overall or resultant force. E.g. If two people push on a door to the right with a force of 80N each the total force is 160N to the right. If a third person pushes back with a force of 50N then the total force is 160-50 = 110N to the right.

25. Speed • Average Speed = Distance/Time • Do not forget your units! Example – A car covers 50 miles in 2 hours. Its speed = 50/2 = 25 miles/hour Example – A person runs for 25secs at 8m/s. Distance travelled = speed * time = 8*25 = 200metres.

26. Distance-Time Graphs • Look at the red line. The speed on the first ‘uphill’ bit is 8/4 = 2m/s. What is the speed on the last section of the graph? What is the speed of the vehicle that made the blue line?

27. Speed-Time Graphs • They look similar to distance-time graphs – be careful! What does this one show?

28. Momentum (1) • Momentum (kgm/s) = Mass (kg) * Velocity (m/s) Example – an 80kg rugby player running at 7m/s has 80*7 = 560 kgm/s of momentum • The more momentum you have the harder it is for you to be stopped. It is easier to stop a running toddler than a fully grown adult!

29. Momentum (2) • A change of momentum is caused by a Force. Change of Momentum = Force * Time for action (kgm/s) (N) (s) Example: A bat hits a stationary ball with a force of 40N for 0.2s. What is the ball’s change of momentum? If its mass is 0.1kg, what is the ball’s new velocity? Change of Momentum = 40*0.2 = 8kgm/s Use this answer to find the speed using the equation on the last page: Velocity = Momentum/Mass = 8/0.1 = 80 m/s

30. Car Safety • The equation Force = Momentum/Time means that if you have a collision in a short time, you will get a larger force on your body to stop you. Car designers insert crumple zones, seat belts and air bags to increase the time it takes for the human body to change momentum and come to a stop. This reduces the Force on the body so survival is more likely.

31. Laws of Motion • 1. If the Resultant Force acting on an object is zero the momentum of an object does not change, e.g. A rocket in space without its engine on will continue at the same velocity forever, or until it hits another planet. • 2. If there is a resultant force acting on an object then its momentum will change, e.g. An aircraft’s engines make thrust which increase the plane’s velocity on the runway so the plane’s momentum is increasing. Note: for the plane in Law 2, once it is travelling at a constant speed in level flight, the thrust of the engines balances the drag on the plane so there is no resultant force and Law 1 now applies.

32. Work and Energy • Work done is another expression for Energy Transferred. Work and Energy are measured in Joules. Work Done (J) = Force (N) * Distance Moved (m) Example: A trolley is pushed 40m by a 20N force. Work done = 20*40 = 800N. When lifting things up we are giving them Gravitational Potential Energy and can also use the above calculation, remembering that the Force you will be lifting is the Weight of the object: Gravitational Potential Energy = Weight * Height moved

33. Kinetic Energy • Kinetic Energy = ½ * mass * velocity2 (J) (kg) (m/s) Example: A runner of mass 60kg is moving at 5m/s. What is their Kinetic Energy? KE = ½ * 60 * 52 = 750J

34. Energy transfers • As you remember from KS3, energy can be transferred from one form to another. If we take a ball of mass 0.5kg (weight 5N) to the top of an 8m building, how fast will it be travelling when it hits the floor? • Gravitational Potential = 5*8 = 40J • When the ball drops, just before it hits the floor we assume all the Grav Pot energy has become Kinetic as the ball is moving at maximum speed. • So Kinetic Energy as ball hit floor = 40J • 40 = ½ * 0.5 * velocity2 • 160 = velocity2 • Velocity = 12.6m/s

35. Physics Equations to learn 1. Average Speed = Distance/Time 2. Momentum (kgm/s) = Mass (kg) * Velocity (m/s) 3. Change of Momentum = Force * Time for action (kgm/s) (N) (s) 4. Work Done (J) = Force (N) * Distance Moved (m) 5. Gravitational Potential Energy = Weight * Height moved 6. Kinetic Energy = ½ * mass * velocity2 (J) (kg) (m/s)