2611 Shares

i need help with science homework!?

Topic: i need help with science homework!?
June 25, 2019 / By Delphina
Question: This is exactly what it says in the text book! 1. a dish of sugar and water is left in the sun for a few days, the solution has disappeared and a white residue remains on the dish. Has a physical or chemical taken place? 2. How can you prove that the law of conservation of mass is used when using two solutions? Help! thanks

Best Answers: i need help with science homework!?

Caileigh | 6 days ago
1 its a physical change. The sun evaporates the water leaving behind the Sugar. Therefor not a chemical change, 2 When using the law of conservation there is always a yield. The chemical formula has to be equaled some how in order for the law of conservation of mass to work Yield = what you get after the chemical change.
👍 280 | 👎 6
Did you like the answer? i need help with science homework!? Share with your friends
Originally Answered: How could every major science academy, university science dept. & science textbook writer be corrupted?
Of all the arguments I've read, the 'scientists are lying to us' one is far and away the most ridiculous, badly thought-out, infantile, intellectually abhorrent load of nonsense I've heard. It just doesn't make any sense. Repeating it ad infinitum does not make it true, it simply makes people look increasingly desperate and idiotic. Here's why: 1. If I went to a research agency and said 'I want to study whether the earth is flat or not' they'd laugh at me. The reason why is because there is a general consensus that the earth is not flat. So, here's the first problem - why would scientists AGREE on AGW? It makes much more sense for them to muddy the waters, to disagree on this issue, because having no definitive answer or having large-scale disagreement on a scientific issue ensures more funding to research it! 2. The scientists we remember are the ones who disagreed with the mainstream view. We remember Newton because he decided that instantaneous velocity wasn't a stupid concept and developed calculus to examine it. And in doing so he changed forever how we view motion and forces. We remember Einstein because he said 'actually, Maxwell's equations prove the speed of light is constant in all frames of reference' when just about everyone else was trying to show that it wasn't. So it makes no sense at all for scientists to agree ... if they disagreed on AGW, and someone came up with a theory that matched all the data, did away with our emission of CO2, and showed the physics behind it, well, that person would ride the lecture circuit for years and make lots of money. So there's no financial or personal incentive for scientists to all agree. 3. Scientists are taxpayers too. The way some people talk, you'd think scientists lived on their own little island. They don't. They're people like everyone else who drive cars, pay mortgages, have kids, go on holiday, pay for gas, electricity, etc. So why, exactly, would thousands of taxpayers DELIBERATELY put forward a theory if the consequences of dealing with that theory would harm industry, the economies of the countries they live in, their take-home pay, the cars they could drive, etc. 4. If scientists wanted to make money, they could just reverse position, go to the oil companies and say 'look, for one million a year I'll publish whatever you say you want. I'll fudge my data, I'll write the papers, I'll bribe and cheat and bluff, but I'll do it for hard cold cash'. So why would thousands of scientists do the exact opposite of the thing petrochemical companies would pay through the nose for them to do? 5. If scientists are lying to us, then they're using public money to send satellites into orbit, fudging the data, deliberately hiding the truth from us, and making false conclusions. That's fraud in any language, so why would thousands of people risk being sentenced to jail-time for misappropriating public funds? I don't buy it. If you wanted to push an eco-agenda then coming up with something that will affect the planet severely after you die isn't a great idea. I mean, if you wanted to, why not just say 'THAT hurricane was global warming in action'? Why show a graph with a 15 year flat spot, if you believe the deniers arguments? If you want to make money, agreeing with other scientists and blaming the biggest companies on the planet isn't a good way to go. So this argument that 'scientists are lying to us' is just people being intellectually lazy and saves them having to actually understand the science. Now, some people here have argued that they don't believe the scientists because scientists have been wrong in the past. Actually, when you look at it, they haven't. We might have replaced Newton's ideas but they're not wrong ... we still use Newton's law of gravity to send spacecraft to other planets, we still use Newton's laws to model cars moving around a racetrack, or to determine the rate at which something falls. Maxwell's equations might have been replaced by quantum electrodynamics, but we still use Maxwell's equations to explain the dipole radiation pattern of a radio antenna, and in applications such as radar, mobile phones, and digital electronics. Scientific theories model the data we have at the time. The data tells us our planet is warming. Modelling that data correctly involves us factoring in CO2 emissions by human activities. You can't say 'that's nonsense' until you actually show it's nonsense. Which is the difference between real science, and the pseudoscience of speculation all talk and no pants of the deniers.

Almira
Not giving answers, but helping... 1. A physical reaction involves a change in state, such as from solid to liquid or from liquid to gas. A chemical reaction involves the interaction of two chemicals to form something else. Think about it. You leave a dish of sugar and water in the sun and the water goes away. Did the water react with the sugar to form another chemical? Did the water maybe just evaporate, leaving only the sugar? decide what happened and choose which type of reaction it was. 2. First of all, what is the law of conservation of mass? Isn't it something like, the total mass won't be gained or lost in a chemcial reaction? So how would you prove this when using two solutions? Would you maybe weigh each one before and the result after? Or measure it some other way?
👍 120 | 👎 -1

Valentine
A physical change in a substance doesn't change what the substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed. For example, if a piece of paper is cut up into small pieces it still is paper. This would be a physical change in the shape and size of the paper. If the same piece of paper is burned, it is broken up into different substances that are not paper. Physical changes can be reversed, chemical changes cannot be reversed with the substance changed back without extraordinary means, if at all. For example, a cup of water can be frozen when cooled and then can be returned to a liquid form when heated. So It Makes it Chemical change.
👍 115 | 👎 -8

Roly
1. A chemical change means that the molecular structure of the substance has been altered. Does dissolving sugar in water make it not sugar? Does it change the sugar into something else? 2. Conservation of mass means that no matter is destroyed or created. So the mass of the system stays the same throughout.
👍 110 | 👎 -15

Mitch
1) Its a physical change because the water has simply evaporated and the change is not irreversible, means that you can condense the evaporated water and make that solution again. 2) I don't get ... sorry. Is there anything else written there?
👍 105 | 👎 -22

Originally Answered: I need help with my science homework?
First you find the volume of the oxygen: 1.17g * 1cm^3/0.0013g = 900cm^3 Then substitute that value for V in the volume equation: 900cm^3 = (4/3)(pi)(r^3) divide both sides by (4/3)(pi) 214cm^3 = r^3 now take the cube root of each side (raise each to the 1/3 power) 6cm = r and the diameter is 2x the radius, so 12 cm is your answer.

If you have your own answer to the question i need help with science homework!?, then you can write your own version, using the form below for an extended answer.