Matter and Physics

1. Matter and Physics

2. Solids Crystal Structure Crystals are a regular arrangement of atoms of a solid Regular geometric shape Regular spacing between

3. Solids Discovered. by X-rays that pattern was regular X-rays through crystal bend around atoms Ionic and metal crystals are simple Organic crystals much more complex

4. Density Lightness or heaviness Does not change if material is broken Does change if material is compressed

5. Density D = m/v Determined by mass of atoms and their spacing Osmium most dense element due to close spacing Density of water = 1 g/cm3 by definition Weight density is similar, weight / volume

6. Elasticity Stretching ability plus ability to return to its original shape Materials which deform and do not return to shape are inelastic

7. Elasticity Stretch of a spring is directly proportional to applied – Hooke’s Law - F = kx There is a limit to which stretched will return - elastic limit - why a Slinky must be replaced

8. Compression and Stretching In solids, like steel, placed horizontally top and bottom behave opposite There is always a point between with no stretch or compression - a neutral layer

9. Compression and Stretching ‘ I ’-beam girders take advantage of this - neutral layer in ‘ I ’ area in center much less weight for same strength

10. Scaling Relationship between size and, weight, strength, and surface area Ant is much stronger for its size than an elephant Elephant size ant would be very weak - it isn’t built for increased size Objects which are larger are much heavier than stronger Strength depends on the cross section area Weight depends on volume Volume (cubic measure) grows faster than area (square measure) Area: 22 = 4 Volume: 23 = 8 Density makes mass and volume proportional

11. Scaling Large animals must have greater area to hold their greater weight -elephant vs. deer, ant vs. tarantula King Kong could not be strong due to scaling - science fiction

12. Scaling Surface area grows slower than volume also Elephant ears for cooling make up for lack of elephant surface area Cells must divide to increase surface area for life Surface area makes small animals fall without damage Chemical reactions take place faster with more surface area

13. Homework RQ 2, 4, 7, 8, 11, 12, 18, 19 T&E 3, 6, 9, 10

14. Liquids Pressure in liquids Pressure is force per unit area For liquids, pressure on bottom of container equals weight density times depth of liquid

15. Liquids The pressure is same for the same liquid at the same depth no matter the volume At 5 feet in a small lake is same as at 5 feet in the ocean Depth causes pressure to be greater in a deep pool vs. a shallow one A container with holes filled with liquid, liquid sprays farthest from the lowest hole due to higher pressure

16. Buoyancy Objects underwater are easier to lift than above surface Water is exerting an upward force called buoyant force Caused by water pressure greater beneath object than above it Floating occurs due to this force If weight > buoyant force - object sinks If weight = buoyant force – object remains at any level (fish) If weight < buoyant force - object floats

17. Buoyancy Water is displaced by a submerged object Amount displaced = volume of object Use this to find volume of irregular objects

18. Buoyancy Archimedes Principle Immersed object is buoyed up by force equal to displaced True for both liquids and gases - both are fluid Immersed = either totally or partially submerged Causes apparent weight difference 300g block = 3N Displaces 2N if submerged 3N - 2N = 1N apparent weight in liquid

19. Buoyancy Archimedes principle depends on volume rather than weight of object -density of object Submarines take water in or let it out Fish change size of air sac Crocodiles swallow stones to get lower

20. Floatation Ship can be made of iron or even concrete and still float.

21. Floatation Shape causes larger volume and more buoyant force. Floating object displaces fluid equal to its own weight.

22. Pascal's Principle Changes in pressure at any point in an enclosed fluid at rest are transmitted to all parts and act in all directions This principle is used in hydraulic equipment everywhere pressure in pressure out

23. Pascal's Principle Can be used to increase force – by same simple machine principle – 1N moves greater distance to induce 50 N output Lift for cars in gas station or elevators in buildings can be done by this effect

24. Homework RQ 1, 2, 3, 6, 12, 13, 14, 15 T&E 2, 3, 5, 6, 7, 10