How can you tell that a chemical change has happened? Provide examples from your life and explain what indicates something has happened chemically.
There are 5 major signs that can indicate that a chemical reaction has occurred. There may be one or multiple signs together to signify a chemical change. In no particular order these signs are change of color, change of odor, change of temperature, production of a gas and production of a precipitate. Fire is an excellent example of a change in temperature and a change in smell as well as the production of a gas. As the wood burns it releases large amounts of heat as the bonds of the cellulose fibers break down into carbon dioxide, carbon monoxide and just plain carbon. Note also that the change in color from brownish to black once burned (or gray ash) indicates a color change and the wood definitely smells different before than it does as the charcoal after, or the smoke during. Leaves during the fall change colors from green, photosynthesizing machines full of chlorophyll inside their little chloroplasts, to oranges, yellows and reds, more capable of collecting the change in the most common frequencies of the sunlight as, in the northern hemisphere, the sun passes through more and more atmosphere as the earth gradually tilts the northern hemisphere away from it's life giving rays. Eventually to save water and energy, deciduous trees shed their leaves in deep winter and regrow them in spring.
Do fish breathe? Explain your answer and provide examples.
Breathing is the inhaling and exhaling of air (or other gases). Respiration is the process by which a n organism obtains and uses energy. To do this, many living things, including fish and humans, need oxygen to perform the processes of cellular respiration. The oxygen is used as the final acceptor of electrons during the creation of ATP, which is the energy that powers our bodies at a cellular level. Oxygen is obtained through the process of breathing for humans, although not for all animals. Some animals obtain oxygen through gills while other organisms can obtain the oxygen they need through their outer membranes, absorbing it from the environment. Fish, like all animals, need oxygen to produce the energy molecules ATP, however since they get their oxygen passively from water passing over their gills, technically, they don't breathe.
Explain why it would take less force to move an object a greater distance. How would this relate to your experience in the real world? Please give one example where you have experienced this phenomenon and explain how it relates to the above question.
Work is defined as Force multiplied by distance. If work is kept as a constant then the other two variables are inversely proportional to one another. As we increase the distance within a simple machine such as a ramp, the amount of force needed to move a mass to a given height would be reduced. the longer the ramp, the less force would be needed. I have experienced this while hiking up mountain paths in the north cascade wilderness. If I were to have to climb straight up the mountain, the force I would need to raise my body 1000 feet of vertical would be significant. Switchbacks allow for the hiker (me) to spend less force to climb my mass to the same height, making for a much more enjoyable experience, especially while carrying a 60 pound pack. The switchbacks are much longer ramps going back and forth across the vertical direction of the mountain. Each step moves up only a few inches instead of 3 feet, but the path is much longer allowing for less force over a greater distance while hiking.