P.S. - LIQUID BASICS #6

Liquid Basics

The second state of matter we will discuss is a liquid. Solids are things you can hold that maintain their shape. Gases are floating around you or trapped in bubbles. What is a liquid? Water is a liquid. Your blood is a liquid. Liquids are an in-between state of matter. They can be found between the solid and gas states. They don't have to be made up of the same molecules. If you have a variety of materials dissolved in a liquid, it is called a solution. 

One characteristic of a liquid is that it will fill up the shape of a container. If you pour some water (H₂O) in a cup, it will fill up the bottom of the cup first and then fill the rest. The water will also take the shape of the cup. The top part of a liquid will usually have a flat surface. That flat surface is the result of gravity pulling on the molecules. Putting an ice cube (solid) into a cup will leave you with a cube in the middle of the cup because it is a solid. The shape of the solid cube won't change until the ice becomes a liquid. 

Another trait of a liquid is that it is difficult to compress. When you compress something, you measure out a certain amount of material and force it into a smaller space. Solids are very difficult to compress and gases are very easy. Liquids are in the middle, but tend to be difficult. When you compress something, you force the atoms closer together. When the pressure goes up, substances are compressed. Liquids already have their atoms close together, so they are hard to compress. Many shock absorbers in cars compress liquids in sealed tubes. 

Molecules Sticking Together

A special force keeps liquids together. Those intermolecular forces make sure that the molecules of the liquid stick to each other. Solids are stuck together and you have to force them apart. Gases bounce everywhere and they try to spread themselves out. Liquids actually want to stick together. There will always be the occasional evaporation, where extra energy gets a molecule excited and the molecule leaves the system. Overall, liquids have cohesive (sticky) forces at work to hold the molecules together. 

PHASES OF MATTER

PHASES OF MATTER GAME

PHASES OF MATTER #2

PHASES OF MATTER #3

Recall: Temperature is a measure of the average kinetic energy (energy of motion) of all the molecules or atoms in a material. All atoms are in motion to a lesser or greater extent, whether that be atomic vibrations in a rigid solid, or straight line motions in a gas.

In the gaseous state, molecules have so much kinetic energy that they fly off in all directions but repeatedly collide and bounce off of other molecules.
--- boiling temperature - condensation temperature ---
In the liquid state, atoms or molecules have sufficient kinetic energy to overcome the chemical bonds that held them in their crystal lattice and move independently, yet they don't have enough energy to separate completely from other atoms.
--- melting temperature - crystallization temperature ---
In the solid state, chemical bonds are stronger than the kinetic energy of the atoms. The atoms are locked into their crystal lattice positions. ***************************************** REVIEW We learned in some of our other lessons that matter is made up of atoms and molecules. Millions and millions of these tiny objects fit together to form larger things like animals and planets and cars. Matter includes the water we drink, the air we breathe, and the chair we are sitting on.  States or Phases  Matter usually exists in one of three states or phases: solid, liquid, or gas. The chair you are sitting on is a solid, the water you drink is liquid, and the air you breathe is a gas.  Changing State  The atoms and molecules don't change, but the way they move about does. Water, for example, is always made up of two hydrogen atoms and one oxygen atom. However, it can take the state of liquid, solid (ice), and gas (steam). Matter changes state when more energy gets added to it. Energy is often added in the form of heat or pressure.  Water  Solid water is called ice. This is water with the lowest energy and temperature. When solid, the molecules in water are held tightly together and don't move easily.  Liquid water is just called water. As ice heats up it will change phases to liquid water. Liquid molecules are looser and can move about easily.  Gas water is called steam or vapor. When water boils it will turn to vapor. These molecules are hotter, looser, and moving faster than the liquid molecules. They are more spread apart and can be compressed or squished. The three states of Water More States  There are actually two more states or phases that matter can take, but we don't see them much in our everyday life.  One is called plasma. Plasma occurs at very high temperatures and can be found in stars and lightning bolts. Plasma is like gas, but the molecules have lost some electrons and become ions.  Another state has the fancy name Bose-Einstein condensates. This state can occur at super low temperatures.  Fun Facts about Solids, Liquids, Gases Gases are often invisible and assume the shape and volume of their container. The air we breathe is made up of different gases, but it is mostly nitrogen and oxygen. We can see through some solids like glass. When liquid gasoline is burned in a car, it turns into various gases which go into the air from the exhaust pipe. Fire is a mixture of hot gases. Plasma is by far the most abundant state of matter in the universe because stars are mostly plasma. STATES OF MATTER

P.S. - SOLID BASICS #5

Solid Basics

So, what is a solid? Solids are usually hard, because their molecules have been packed together. You might ask, "Is baby power a solid? It's soft and powdery." Baby power is also a solid. It's just a ground down piece of talc. Solids can be hard, soft, big or small like grains of sand. The key is that the solids hold their shape and they don't flow like a liquid. A rock will always look like a rock unless something happens to it. The same goes for a diamond. Even when you grind up a solid into a powder, you will see tiny pieces of that solid under a microscope. Liquids will flow and fill up any shape of container. Solids like their shape. 

In the same way that a solid holds its shape, the atoms inside of a solid are not allowed to move around too much. This is one of thephysical characteristics of solids. Atoms and molecules in liquids and gases are bouncing and floating around, free to move where they want. The molecules in a solid are stuck in a specific structure or arrangement of atoms. The atoms still spin and theelectrons fly around, but the entire atom will not change position. Solids can be made up of many things. They can have pure elements or a variety of compounds inside. When you get more than one type of compound in a solid it is called a mixture. Most rocks are mixtures of many different compounds. Concrete is a good example of a man-made mixture. 

Granite is a mixture you might find when you are hiking around a park. Granite is made up of little pieces of quartz, mica, and other particles. Because all of the little pieces are spread through the rock in an uneven way, scientists call it a heterogeneous mixture. This is important because there are different concentrations of specific particles in different parts of the rock. In one place there might be a lot of quartz and very little feldspar, but only a few inches away those amounts might flip. 

Crystals

On the other end of the spectrum from a mixture is something called a crystal. When a solid is made up of a pure substance and forms slowly, it can become a crystal. Not all pure substances form crystals, because it is a very delicate process. The atoms are arranged in a regular repeating pattern called acrystal lattice. A crystal lattice is a very exact organization of atoms. A good example is carbon (C). A diamond is a perfect crystal lattice of carbon, while the graphite arrangement of carbon atoms is a more random and disorganized. You can find graphite in your pencils. For carbon, those two different structures (crystal lattice vs. random arrangement) are called allotropes. 

P.S. - CHEMICAL VS. PHYSICAL CHANGES #4

Chemical vs. Physical Changes

It is important to understand the difference between chemical and physical changes. The two types are based on studying chemical reactions and states of matter. We admit that some changes are obvious, but there are some basic ideas you should know. Physical changes are about energy and states of matter. Chemical changes happen on a molecular level when you have two or more molecules that interact and create a new molecule or two. 

When you step on a can and crush it, you have forced a physical change. The shape of the object has changed. It wasn't a change in the state of matter, because the energy in the can did not change. When you melt an ice cube (H₂O), you have also forced a physical phase change by adding energy. That example caused a change in the state of matter. You can cause physical changes with forces like motion, temperature, and pressure. 

Looking at Molecules

Chemical changes happen on a much smaller scale. While some experiments show obvious chemical changes, such as a color change, most chemical changes that happen between molecules are not seen. When iron (Fe) rusts, you can see it happen over a long period of time. The actual molecules have changed their structure (the iron oxidized). Melting a sugar cube is a physical change, because the substance is still sugar. Burning a sugar cube is a chemical change. Fire activates a chemical reaction between sugar and reactions (O₂). The oxygen in the air reacts with the sugar, and the chemical bonds are broken. 

Some chemical changes are extremely small. They happen over a series of steps. The result might have the same number of atoms, but it will have a different structure or combination of atoms. The sugars glucose, galactose, and fructose all have six carbon atoms, twelve hydrogen atoms, and six oxygen atoms (C₆H₁₂O₆). Even though they are made of the same atoms, they have very different shapes and are called structural isomers. Those isomers have atoms bonded in different orders. Also, each of the sugars goes through different chemical reactions because of the differences in their molecular structure. Scientists say that the arrangement of atoms allows for a high degree of specificity, especially in the molecules you find in living 
things.
 


A physical property is an aspect of matter that can be observed or measured without changing it. 

• Examples of physical properties include color, molecular weight and volume.

A chemical property may only be observed by changing the chemical identity of a substance. This property measures the potential for undergoing a chemical change. 

• Examples of chemical properties include reactivity, flammability and oxidation states.

Physical changes involve states of matter and energy. 

• No new substance is created during a physical change, although the matter takes a different form. 
• The size, shape, and color of matter may change. 
• Also, physical changes occur when substances are mixed, but don't chemically react. One way to identify a physical change is that such a changes may be reversible, especially phase changes. For example, if you freeze an ice cube, you can melt it into water again. 

This is a list of 10 examples of physical changes.

1. crushing a can
2. melting an ice cube
3. boiling water
4. mixing sand and water
5. breaking a glass
6. dissolving sugar and water
7. shredding paper
8. chopping wood
9. mixing red and green marbles
10. sublimating dry ice 

Chemical changes involve chemical reactions and the creation of new products. Typically, a chemical change is irreversible. 

This is a list of 10 examples of chemical changes.

1. rusting of iron
   
2. combustion (burning) of wood
   
3. metabolism of food in the body
   
4. mixing an acid and a base, such as hydrochloric acid (HCl) and sodium hydroxide (NaOH)
   
5. cooking an egg
   
6. digesting sugar with the amylase in saliva
   
7. mixing baking soda and vinegar to produce carbon dioxide gas
   
8. baking a cake
   
9. electroplating a metal
   
10. using a chemical battery