Physical And Chemical Changes Essay, Research Paper

Purpose: To conduct experiments and to determine whether they are physical or chemical changes

Pre-Lab Notes:

Before we conduct these experiments there are some topics that we must discuss. As I stated in the purpose, in this lab we are going to be looking at some experiments, and we have to determine whether they are a cause of chemical or physical changes. The purpose for all the labs that we will be doing will be the same. During a chemical change a new substance is formed, it is irreversible, and it is usually accompanied by energy changes. In comparison, during a physical change no new substance is formed, it is easily reversible, and it is usually accompanied by energy changes. An example of an energy change would be heat or light. Just to give you can example of a chemical change this would be burning a piece of wood. This is because the wood is mixed in with oxygen to make a change. The name of the starting substances during a chemical change is reactants and the name of the new substance is the product. An example of a physical change would be water to ice, because the ice can easily be changed by into water, but by the change of temperature this physical change occurs. When mixing chemicals together it is important to understand what solvent and solute is. Solute is the solid that is dissolved in the liquid. The name of the liquid is the solvent. It is important to know this, because in experiment one mixed solvents and solutes together quite frequently. Before conducting any experiment it is very important to take note of what type of state ones materials are in. There are three different types of states that we will look at now are Solid, Liquid, and Gas. A solid has a definite shape and is tightly packed and very close to each other that they can’t move. An example of a solid would be a desktop. A liquid flows very easily and takes on the shape of its container. A liquid?s particles are less packed together compared to a solid, and are able to slide past each other and an example of a liquid would be water. The last state that we need to go over is gases. A gas is able to expand and take on the shape and volume of its container. Gas has particles very loosely collected and able to move freely with space between them, which makes it different from the other two states. An example of a gas would be oxygen. When matter goes from a solid to a gas this is called sublimation. Not many substances can go through sublimation. The opposite of sublimation is disposition. This is when matter goes from a gas state to a solid state. These three terms are important to know, because during physical and chemical changes the state of one object often changes, (refer to page one of attachments to compare the diagrams of a solid, liquid and gas). We are going to conduct a series of eight experiments and now that we have all of this background information we will be completely ready to start.

Lab #1

Title: Physical and Chemical Changes

Materials:

Candles

Aluminum foil

Matches

Procedure:

1. put a piece of aluminum foil on the bottom of the candle

2. light the candle

3. observe what happens

Hypothesis: Will be a physical change, because it can be reversed by cooling, no new substance is formed.

Observations:

BEFORE LIT

Clearly has been used before

2.5 inches long

Piece of tin foil is on the bottom

The wick is black

The candle is in a solid state

ONCE LIT

The light is burning bright and strong

Wax is beginning to form (liquid state)

Smell of smoke as a result of the fire mixing with oxygen

Heat is coming from flame

Analysis: The candle did stay in the same state and no new substance was formed. Before trying this experiment the wick was black and clearing it went through some sort of change, probably because it was mixed with Oxygen in the air. When I observed the candle I couldn?t understand the relevance of the aluminum foil. It didn?t seem to be important to me because I didn?t observe the candle until it was fully melt. Maybe there would have been some sort of reaction between the candle, wick and aluminum foil if we waiting for it to burn down.

Conclusion: The hypothesis was correct in that the candle went through a physical change. I do though think that the wick went through some sort of chemical reaction because the wick was burnt, which is a sign of a chemical change. The wick can never be turned back to its normal start which is a sign of a chemical change.

LAB #2

Title: Physical and Chemical Changes

Materials:

Watch glass

Stirrer

Copper Nitrate (Blue Color)

Sodium Carbonate (clear)

Procedure:

1. Put 2 drops of each chemical on the extreme ends of the watch glass ( don?t let them touch)

2. Put a piece of white towel on the bottom ( so you can see more clearly)

3. Use stirrer to put 2 chemicals together

Hypothesis: Chemical change

Observations:

The color became lighter

Analysis: When the two chemicals were mixed together the color is the online thing that changed. The color became a light blue color.

Conclusion: this project was clearly chemical because a new substance was formed and it can not be changed back to its original state. It was not accompanied by energy changes, but not all-chemical changes are.

LAB #3

Title: Physical and Chemical Changes

Materials:

2 test tubes

Test tube rack/ 9 holders

Barium Chloride (colorless)

Inc Sulfate (colorless)

Procedure:

1. Put a small amount of the solution in one tube.

2. Put the other solution in the other test tube.

3. Pour them into each other

Hypothesis: chemical change.

Observations:

Once put together a milky white substance began foaming

Residue was left of the sides of the test tube

Looks like a thicker substance

Unable to look through the test-tube like before

Analysis: the two substances were able to form a milky substance. This experiment is clearing a chemical change because a new substance was made and it is irreversible.

Conclusion: Like the last experiment this substance was a product of mixing two reactants to make a new product, and they both were chemical changes.

LAB # 4

Title: Physical and Chemical Changes

Materials:

Beaker

(Copper) cupric chloride crystals

Aluminum foil

Stirrer

Water

Scoop

Procedure:

1. put a small amount of cupric chloride with a scooper in the beaker

2. Dilute it with water

3. Stir solution

4. Observe solution

5. Take a piece of aluminum foil into solution

Hypothesis: chemical change

Observations:

Color is light blue/ green

Tin foil is bubbling and turning a clack color

Black flakes are coming off of the piece of foil

Tin foil has become a light red color

Steam is found on the edge of the beaker

Tin foil has a soft texture

Analysis: During this lab the tin foil clearly went a chemical change. A new substance was formed and it even started to foam.

Conclusion: this was the coolest experiment so fair. The way the chemicals reacted to the foil was amazing. The color of the foil and the texture was different after it was placed in the solution. There is no way that the tin foil would be able to return to its first state.

LAB #5

Title: Physical and Chemical Changes

Material:

Beaker

Cupric Sulfate Solution

Thongs

Wire gauze

Burner

Procedure

1. Put a little amount of solution in a beaker.

2. Heat it until boils

3. Take it off the heat

4. Add water (the amount that evaporated)

Hypothesis: chemical change

Observations:

When water evaporated the substance in the beaker was a white color

When the water was re-added water to the beaker the color turned back to its original state

Steam was clearly on the sides of the beaker

Analysis: This experiment was a physical change because it was able to return to its first state. We also required energy (heat) when we conducted and that is one of the ways that we can determine that it is a physical change. There also wasn?t a new substance that was formed. We simply evaporated the water and then we re-added water to show that we could go back to the regular state. We also know that there is water in the cupric sulfate solution because when it was heated it evaporated.

Conclusion: my hypothesis for this experiment was wrong. In the past experiment I saw a pattern that when a solution is mixed together it is a chemical change, but that isn?t always the case.

LAB #6

Title: Physical and Chemical Changes

Materials:

Magnesium ribbon

Burner

Tongs

Evaporating Dish

Procedure:

1. Take a piece of ribbon w/ tongs.

2. Put it into the burning flame

3. Immediately put into evaporating dish

4. Observe what happens

Hypothesis- chemical change, because when you burn something there is no way that you can get it back to its original state.

Observations:

A bright/ white flame was visible as a result

A white substance remained on the thongs

The ribbon turned a white and black color

Analysis: I was correct in my hypothesis in that it is a chemical change. There was a new substance that occurred as a result of this experiment and there is no way that we could change it back to the ribbons original state.

Conclusion: The magnesium ribbon is the only type of ribbon that will bring that bright light when put into a flame. This was a great lab and it was so cool to observe.

LAB #7

Title: Physical and Chemical Changes

Materials: Sodium Carbonate/ solid

Hydrochloric acid

Test tube

Scoop

Test tube rack

Procedure:

1. Put a bit of sodium carbonate in the test-tube with a scoop

2. Pour some hydrochloric acid in test tube

Hypothesis: bubbles will occur and chemical change

Observations:

Complete bubbling occurrence

Crystals on bottom starting to dissolve

Little bubbles coming up

Analysis: This experiment was clearing a chemical change because they substances couldn?t be changed back to their original state. Something chemical also must have occurred in the test-tube for it to bubble and continue to bubble like it did.

Conclusion: This was a fun lab because I took an educated guess and I was correct! So far what we have seen is that a lot of the mixtures that we put together are chemical changes, except if we add water. This was a great lab!

LAB #8

Title: Physical and Chemical Changes

Materials:

Iodine (solid crystals)

Evaporating dish

Bunsen burner

Procedure:

1. put some iodine crystal in beaker

2. take a cube of ice and place it in evaporating dish

3. place evaporating dish on the top of the beaker

4. place it on the burner, ass heat

Hypothesis: Chemical change

Observations

Beaker is turning purple?darker on the bottom of the beaker

All gas and no liquid

Ice is slightly melted

Turned from solid to gas

After time and heat is off it is becoming clear

Crystals on bottom of the evaporating dish

Purple gas is coming out of beaker

Analysis: in this project it was very cool how the crystals appeared on the cover of the evaporating dish. The iodine was in a solid state and it changed into a gas. This goes back to the pre-lab notes and shows that matter can change to many different states. Not many substances can go through sublimation like we have seen in this experiment.

Conclusion: I believe that I was wrong in this experiment, because I believe that this experiment is physical because it is reversible. The iodine is able to go from gas to solid. When doing this experiment it was very important not to open up the beaker because alcohol is flammable and it could have caused a fire. When the solution was heated it when up to the top to try to evaporate and it was cooled, due to the ice on the top.

Final Thought:

After doing these eight experiments I feel as though I have a strong grasp on physical and chemical changes. I found that it is very important to go though the checklist of both physical and chemical changes before coming to a conclusion. A trend that I found was that when two chemicals were mixed together without water they mixture was chemical. This is because there is no way to get the solution back to its first state. When mixing the only way it can be chemical is if it is one chemical mixed with water. The reason this is physical is because one can evaporate the water and then re-add it. It was a lot of fun conducting these experiments and I look forward to many more in the future.

4af

Atkin, Beth. Voices From The Feilds. Boston: Little,Brown and Company, 1993

Ashabranner,Brent. Still A Nation of Immigrants New York: Cobblehill Books, 1993

Poppins, Joyce. Sneaking into Country. New York: Chelsea House Publishers, 1998

Garza, Hedda. Latinas. Chicago: Franklin Watts, 1994