In science this week, we started talking more about atom behavior and things like that. We discussed pure substances, mixtures, and chemical reactions.
Basics
Review:
- A pure substance has definite chemical and physical properties.
- Matter is anything that has mass and takes up space.
- Compounds are pure substances composed of two or more different elements.
- Elements are made up of one type of atom and they are pure substances.
- Water is a pure substance.
Mixtures
Mixtures are two or more pure substances that are not chemically combined. You can physically separate them. Their components have different properties. There are two types of mixtures.
Homogeneous mixtures
Homogeneous mixtures are the same throughout. Examples of them are:
- Milk
- Tomato soup
- Blood
- Salt water
- Lemonade
- Air
You cannot see their separate parts, but you can separate them.
Heterogeneous mixtures
Heterogeneous mixtures are different throughout. The best way to tell the two types apart is that Heterogeneous mixtures are chunky, and Homogeneous mixtures aren’t. You can see the separate components, so therefore they are easier to separate. Examples are:
- Pizza
- Fruit salad
- Cereal with milk
- Salad
- People
People are heterogeneous mixtures. Can’t you take out the eyes, the teeth, each separate component? It would be painful, but you could. You can take olives off of pizza if nobody like olives. You can take the grapes out of the fruit salad. You can see the separate parts, so it is easier to separate them.
We had to determine each item below to see which ones are mixtures, compounds, or elements. Before looking at the answers, why don’t you try and figure them out yourself?
- Rocks
- Pure water
- Copper
- Aluminum
- Jelly beans
- Lemonade
- Table sugar
- Silver
- Diamond
- Sand
- Tea
- Salt
- Neon
- Salad
To separate homogeneous mixtures (which are very hard to see the parts) you heat it.
Counting atoms
Each element symbol has no more than two letters, one uppercase, one sometimes lowercase, and no numbers.
Example: NaCl. There are two capital letters, so you know that there are two elements.
Subscripts
Subscripts are the little numbers in the formula. The number tells us how many atoms of the element before the subscript. Like the formula H2O. We know that there are two Hydrogen atoms because of the subscript. If there is no subscript, like in the Oxygen part of the formula, the value of the subscript is 1, not 0.
Coefficients
The coefficient is the big number in front of the whole formula. Don’t mistake that for a subscript. It is something completely different. The coefficient is applied to the entire formula. So if we had 4H2O, the coefficient would be the four at the front of the formula. Multiply the number (4) by EVERY SINGLE SUBSCRIPT IN THE ENTIRE FORMULA. So since there is the 2 after the H, then we multiply 2X4 and we get eight hydrogen atoms. We have four oxygen atoms because we multiply the one by the four.
S&EP: SP5, Using Mathematics
This week, we were given a sheet to do with a bunch of science formulas on it. But we had to use math to solve to equations using what we had learned. It was very fun. We had to do it in one period, but once you got the hang of it, it was very fun. I liked it a lot.
XCC: Patterns
We had to use the patterns to figure out the answers to the problem. We had to label the element, drop down the coefficient, and add the multiplication problem. All you have to do from there was multiply, add the sums, and that is what the answer was. It was basically the same thing over and over, but it was fun.
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