Pages 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 11524 result(s) returned

Upper Beginner #24 - Feasting on the Bullet Train in Japan
Learn Japanese with JapanesePod101.com! The person sitting across from you on the six-hour Japanese bullet train ride has been eating Japanese snacks since you left the station. He has devoured everything the Japanese cart attendant has brought by, from Japanese crackers to fish, and he has probably eaten more than you do in an entire [...]
Author(s): JapanesePod101.com

License information
Related content

Rights not set

Meanings of the Election Results (Podcast)
Description not set
Author(s): jenmhill

License information
Related content

Rights not set

Reuters Asks: Key European political flashpoint of 2013?
Dec. 3 - Senior fund managers tell us what they think will be the key European political flashpoint of 2013
Author(s): No creator set

License information
Related content

The Marxian Doctrine of "Ideology"

[This article is excerpted from volume 2, chapter 12 of An Austrian Perspective on the History of Economic Thought (1995). An MP3 audio file of this chapter, narrated by Jeff Riggenbach, is available for download.]

Author(s): Creator not set

License information
Related content

Rights not set

Glucose Fuel Cells: Brain-Implantable Electronic Devices that Run Like the Brain

"Glucose Fuel Cells: Brain-Implantable Electronic Devices that Run Like the Brain": Video component of the Application for the 2012-2013 Lemelson-MIT Student Prize, by Benjamin I. Rapoport.

 

Author(s): No creator set

License information
Related content

Introduction to microscopy
This free course provides an introduction to microscopy and the operation of a simple light microscope, of the type found in histology courses and teaching laboratories. It outlines different methods used for preparing and staining tissue sections for microscopy, and explains how different stains can be used to identify particular cells, pathogens and anatomical structures.Author(s): Creator not set

License information
Related content

Except for third party materials and otherwise stated (see http://www.open.ac.uk/conditions terms and conditions), this content is made available under a http://creativecommons.org/licenses/by-nc-sa/2

5.1 The medical background

Blood pressure is normally tightly controlled in the face of large variations in blood flow required by activities such as vigorous exercise. The diameter of the blood vessels is under the influence of the so-called sympathetic nervous system. Impulses from the brain stimulate the release of a chemical substance, noradrenaline (1), from the nerve-endings close to the vessel walls. The noradrenaline then diffuses to the blood vessel wall, where it interacts with a specific molecular sit
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

2.6 Senses and communication …

Glance down at the second paragraph of this section, where you will find a sentence about the speed at which eyes adapt from bright light to poor light, and the statement that this process takes 20 minutes for the human eye. With your developing sense of scientific enquiry, that might lead you to wonder how it
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

2.4 Staying warm …

In this section, you will meet the term ‘thermal conductivity’ and you will be asked to accept that it is ‘a measure of how readily heat flows from a particular material’. You may be uncomfortable about the lack of detailed explanation of how it is measured and of actual values and units. However, at al
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

2.1 Land versus water

Mammals share a number of biological characteristics that mark them out as members of the class Mammalia. Many of these are adaptations to a life on land. For example:

  • Mammals give birth to young at a relatively advanced stage of development and feed their young on milk.

  • Most mammals have hair, or fur, covering part or all of the body.

  • Mammals have a high metabolic rate and maintain a relatively high and constant body temp
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Learning outcomes

By the end of this unit you should be able to:

  • contrast the physical properties of air and water and describe implications of such differences for aquatic mammals;

  • give examples of the adaptations displayed by aquatic mammals that enable them to hold their breath while submerged for relatively long periods;

  • describe some of the biological differences between pinnipeds, sirenians and cetaceans;

  • discuss the importance of communication b
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Introduction

The versatility of mammals is a central theme of the ‘Studying mammals’ series of units, but surely no environment has tested that versatility as much as the rivers and oceans of the world. Mammals are essentially a terrestrial group of animals, but three major groups have independently adopted an aquatic way of life. In moving to the water, aquatic mammals have had to survive, feed and reproduce using a set of biological characteristics that evolved in association with life on land. This
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

8 Reviewing and reflecting

Figure 55 is a conceptual diagram that summarises this unit. Molecules are made of atoms, so it was with atoms, to the left of Figure 55, that we began. Early in Section 1 they acquired a structure with a positively charged nucleus surrounded by negatively charged electrons. To a chemist, the most important property of an atom is the
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7.5 Summary of Section 7

  1. The equilibrium constant of a reaction is fixed at any particular temperature. It depends only on the natures of the initial reactants and the final products; what happens as reactants change into products has no effect on the equilibrium constant or position of equilibrium.

  2. The rate of a chemical reaction is affected both by the temperature and by the pathway (reaction mechanism) through which reactants change into products. This pathway c
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7.4 Equilibrium positions and rates of reaction in this unit

Section 7 showed that if a reaction is to occur at a particular temperature, two conditions must be fulfilled: its equilibrium constant must be sufficiently large, and its rate sufficiently great. We finish by pointing out how this crucial distinction between the equilibrium constant and the rate reveals itself in Figure 52. The f
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7.3 Is the rate of reaction very slow?

If the equilibrium position is very favourable, then the reason why Reaction 8.1 fails to occur at 525 °C must be that its rate is very slow. Usually, a reasonable response would be to increase the temperature yet further, but the structure and economy of the car gives us little scope to do this. The alternative is to use a catalyst, which leaves the equilibrium constant unchanged, while speeding the reaction up.

Let us look at the changes that take place in the internal energy
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7.2 Is the equilibrium position unfavourable?

The first possibility is that the reaction system has been able to reach chemical equilibrium, but the equilibrium position is not favourable. How does this come about? If equilibrium has been reached, then the forward (left to right) and backward (right to left) reactions are occurring at equal rates. In such a case, we can emphasise the fact by writing the reaction with two opposed, half-headed arrows:

2NO(g) +
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7.1 Introduction

So far, we have concentrated on the electronic and spatial structures of chemical substances, but we have not said much about chemical reactions. Now we turn to the question of why chemical reactions happen. To remind you of the basic ideas, we shall concentrate on one particular reaction which occurs in the modern motor car.

Table 2 shows typical percentages of the main constituents of the exhaust gas that emerges from a modern car engine. The two most dangerous pollutants are carbon
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

6.4 Summary of Section 6

  1. Molecules have a three-dimensional shape. Bulky irregularities in the shape of a molecule around a reactive site can exclude a potential reactant. Such effects are described as steric.

  2. A sufficient refinement of the molecular shape in the region of the reactive site can make that site specific to just one particular reactant. Many enzymes operate in this way.

  3. The shapes of simple molecules can be predicted using valence-she
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

6.3 Valence-shell electron-pair repulsion theory

The theory of molecular shape that we have been working towards is called valence-shell electron-pair repulsion theory (VSEPR theory). When applied to molecules and ions of the typical elements, its success rate is high. Here is a stepwise procedure that you can follow when applying this theory. It is illustrated with the molecule XeF4 and the ion C1O3. Xenon tetrafluoride is one of the select band of noble gas compounds that were unknown before 1962
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Pages 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577