Obi is trying to determine if a powdery, solid substance is an element or a compound. After recording some observations, he strongly heats a sample of the solid over a burner flame. After fifteen minutes, he turns off the flame and allows the sample to cool. He records his final observations in the data table. A 3-column table with 3 rows. The first column labeled observation has entries appearance, mass (g), chemical reaction with weak acid. The second column labeled original sample has entries white solid, 100.0, bubbles. The third column labeled sample after heating has entries white solid, 56.0, no bubbles.
Which is the best explanation of his results?

The heating changed some of the sample to gas, causing the mass to decrease without breaking down the sample. Therefore, the original sample is a compound.
The appearance stayed the same, showing that the sample was not broken down by heating. Therefore, the original substance is an element.
The mass decreased during heating and some of the impurities escaped. Therefore, the original substance is an element.
The chemical reaction with acid changed, showing that the sample was broken down by heating. Therefore, the original substance is a compound.

Which of the following areas have the highest population density? a) quebecb) united statesc) californiad) new york city

Directions you probably already know that people have different ways to organize their ideas. some people make lists or outlines, some draw pictures, while others may combine these two methods. experiment with different note-taking techniques to find the one which works best for you. one common note-taking technique is webbing. webbing uses the sizes of circles to indicate the importance of items. lines are used to indicate the relationships between items. the example below is based on the information presented in a previous lesson. notice that the circle for "geography is" appears at the center of the web. it has larger than the circles that surround it. the "geography " circle is surrounded by smaller circles of earth's atmosphere, earth's climate, earth's surface. notice the lines that connect these items to the concept of geography. notice that the circles surrounding atmosphere are smaller. also observe that the lines that connect the items and indicate the relationships between the items. webbing will you capture the most important points in your lessons. beginning with lesson two, geographic tools: globes and maps, use webbing to take notes on the important information in this unit. hint: it will be easier to complete this project if you take your notes after completing each lesson.

Why is canada's east coast a great fishing area? will name brainliest and 30