Lucy and Jake are two high school students who are curious about physical and chemical properties. They decide to do some experiments with different substances and reactions to learn more about this topic.
They start by collecting some samples of common substances, such as water, salt, sugar, iron, copper, and sulfur. They use a magnifying glass to observe the appearance of each substance, such as its color, shape, and texture. They also use a thermometer to measure the temperature of each substance, and a balance to measure the mass of each substance. They record their results in a table:
| Substance | Color | Shape | Texture | Temperature (°C) | Mass (g) |
|-----------|-------|-------|---------|------------------|----------|
| Water | Clear | Liquid | Smooth | 20 | 100 |
| Salt | White | Cubic | Crystalline | 20 | 50 |
| Sugar | White | Irregular | Granular | 20 | 50 |
| Iron | Gray | Bar | Metallic | 20 | 20 |
| Copper | Brown | Wire | Metallic | 20 | 20 |
| Sulfur | Yellow | Powder | Soft | 20 | 20 |
They notice that the appearance, temperature, and mass of each substance are examples of physical properties, which are characteristics that can be observed or measured without changing the identity of the substance. They wonder what would happen if they changed the physical properties of each substance. They use a stove, a freezer, a hammer, and a knife to heat, cool, bend, and cut each substance and observe what happens.
They see that some substances change their physical properties when they are heated, cooled, bent, or cut. For example, water freezes into ice at 0°C, salt dissolves in water, sugar melts at 186°C, iron rusts when exposed to air and water, copper turns green when exposed to air, and sulfur burns with a blue flame when ignited. They measure the temperature and mass of each substance after the change and record their results in another table:
| Substance | Temperature (°C) | Mass (g) |
|-----------|------------------|----------|
| Water | 0 | 100 |
| Salt | 20 | 50 |
| Sugar | 186 | 50 |
| Iron | 20 | 20 |
| Copper | 20 | 20 |
| Sulfur | 20 | 20 |
They compare the two tables and realize that the mass of each substance is conserved, even when the physical properties change. They also notice that the temperature of each substance changes depending on the amount of heat added or removed. They learn that heat is a form of energy that can cause physical changes in matter, such as melting, freezing, dissolving, and evaporating.
They also notice that some substances undergo chemical changes when they react with other substances. They learn that chemical changes are changes that result in the formation of new substances with different properties and identities. They also learn that chemical changes are often accompanied by signs, such as color change, gas production, temperature change, and odor. They record the names and formulas of the new substances formed in each reaction in another table:
| Substance | Reaction | New substance | Formula |
|-----------|----------|---------------|---------|
| Water | Electrolysis | Hydrogen gas | H2 |
| Water | Electrolysis | Oxygen gas | O2 |
| Salt | Dissolution | Sodium ion | Na+ |
| Salt | Dissolution | Chloride ion | Cl- |
| Sugar | Combustion | Carbon dioxide | CO2 |
| Sugar | Combustion | Water | H2O |
| Iron | Oxidation | Iron oxide | Fe2O3 |
| Copper | Oxidation | Copper carbonate | CuCO3 |
| Sulfur | Combustion | Sulfur dioxide | SO2 |
They compare the three tables and realize that the mass of each substance is not conserved, but the number of atoms of each element is conserved, when the chemical properties change. They also notice that the temperature of each substance changes depending on the amount of heat released or absorbed. They learn that heat is a form of energy that can cause chemical changes in matter, such as combustion, oxidation, and decomposition.
Lucy and Jake are impressed by the experiments and feel that they have learned a lot about physical and chemical properties. They decide to write some questions and answers based on their findings to test their knowledge. Here are some examples:
Q: What are physical properties?
A: Physical properties are characteristics that can be observed or measured without changing the identity of the substance.
Q: What are chemical properties?
A: Chemical properties are characteristics that determine how a substance reacts with other substances to form new substances with different properties and identities.
Q: What are some examples of physical properties?
A: Some examples of physical properties are color, shape, texture, temperature, and mass.
Q: What are some examples of chemical properties?
A: Some examples of chemical properties are flammability, reactivity, acidity, and alkalinity.
Q: What are some examples of physical changes?
A: Some examples of physical changes are melting, freezing, dissolving, and evaporating.
Q: What are some examples of chemical changes?
A: Some examples of chemical changes are combustion, oxidation, decomposition, and synthesis.
Q: What are some signs of chemical changes?
A: Some signs of chemical changes are color change, gas production, temperature change, and odor.
Q: What is the difference between heat and temperature?
A: Heat is a form of energy that can cause physical or chemical changes in matter, while temperature is a measure of how hot or cold an object or substance is.
Once upon a time, there was a young girl named Sarah who loved experimenting with different substances. One day, she decided to mix oil and water in a jar to see what would happen. As soon as she mixed the two substances, she noticed that they did not mix together. Instead, the oil floated on top of the water.
Sarah’s chemistry teacher saw her experimenting and asked her, “Sarah, do you know why the oil and water are not mixing?”
Sarah replied, “Yes, teacher! It’s because they have different physical properties.”
“Very good, Sarah!” said her teacher. “Do you know what kind of physical properties they have?”
Sarah thought for a moment and said, “I think it’s because oil is less dense than water.”
“That’s right!” said her teacher. “Density is a physical property that describes how much mass is in a given volume. Since oil is less dense than water, it floats on top of the water.”
Sarah was excited to learn more about physical properties, so she asked her teacher, “What other kinds of physical properties are there?”
“Well,” said her teacher, “there’s also color, texture, and melting point. Color is a physical property that describes the color of a substance. Texture is a physical property that describes how a substance feels, such as smooth or rough. Melting point is a physical property that describes the temperature at which a substance changes from a solid to a liquid.”
Sarah was fascinated by this and asked her teacher, “Can you give me an example of a chemical property?”
“Sure,” said her teacher. “Think about rusting. When iron rusts, it undergoes a chemical change that results in the formation of a new substance with different properties. Rusting is an example of a chemical property.”
Sarah was amazed by this and couldn’t wait to learn more about physical and chemical properties. She spent the rest of the day experimenting with different substances and thinking about all the different kinds of properties in the world.
Once upon a time, there was a young girl named Emily who loved experimenting with different substances. One day, she decided to mix vinegar and baking soda in a jar to see what would happen. As soon as she mixed the two substances, the mixture started fizzing and bubbling.
Emily’s chemistry teacher saw her experimenting and asked her, “Emily, do you know what’s happening in that jar?”
Emily replied, “Yes, teacher! It’s because of a chemical reaction.”
“Very good, Emily!” said her teacher. “Do you know what kind of reaction it is?”
Emily thought for a moment and said, “I think it’s called a chemical change.”
“That’s right!” said her teacher. “A chemical change is a change that occurs when one or more substances are transformed into new substances with different properties.”
Emily was excited to learn more about chemical changes, so she asked her teacher, “What other kinds of changes are there?”
“Well,” said her teacher, “there’s also physical change. Physical change is a change that occurs when the substance remains the same, but its physical properties change. For example, when you melt an ice cube, it changes from a solid to a liquid, but it’s still water.”
Emily was fascinated by this and asked her teacher, “Can you give me another example of physical change?”
“Sure,” said her teacher. “Think about when you crumple a piece of paper. The paper changes shape, but it’s still paper. That’s an example of physical change.”
Emily was amazed by this and couldn’t wait to learn more about physical and chemical changes. She spent the rest of the day experimenting with different substances and thinking about all the different kinds of changes in the world.
I hope this story helps you understand the concepts of physical and chemical changes better. If you have any more questions, feel free to ask!.