Crux of the Matter - Past Paper

# 5. Crux of the Matter How does matter exist in different states around me? ## OVERVIEW In this lesson, we will: - understand why solids, liquids and gases are different from one another - learn how changes in the state of matter occur among solids, liquids and gases. ## PEP Recall the propert...

# 5. Crux of the Matter How does matter exist in different states around me? ## OVERVIEW In this lesson, we will: - understand why solids, liquids and gases are different from one another - learn how changes in the state of matter occur among solids, liquids and gases. ## PEP Recall the properties of the three states of matter that you have learnt - solids, liquids and gases. Observe the boxes given below. Each box has a fact or an example of one of these three states. Colour the circle provided in each box using the code - red for solids, blue for liquids and green for gases. | State of Matter | Property | |---|---| | Solids | Has no fixed shape and cannot be poured | | Liquids | Flows when poured from one container to another | | Gases | Spreads to fill the entire container | | Solids | Takes the shape of a container, filling it up from the bottom | | Liquids | Has a shape of its own | | Gases | Keeps its shape when moved from one container to another | ## How is matter different in a solid, a liquid, and a gas? Take two cookies. Work with a partner to slowly and carefully break one cookie over a paper napkin or a plate. Try to break the cookie into the smallest bit that you can. Now, compare this bit to the whole cookie and record your observations in comparison table given below. | Property | Whole cookie | Smallest bit of the cookie | |---|---|---| | Appearance | Circle, chocolaty, crunchy | Square, small | | Smell | Nice, flavorful, nutty | Nice | | Taste | Flavorful, tasty | Nice | - If you could somehow keep on breaking the cookie/biscuit into even smaller, microscopic bits, you would eventually reach extremely tiny particles called molecules. These molecules are made up of even smaller particles called atoms. All matter in any state - solid, liquid, or gas - is made of these particles. - The amount of space occupied by the particles in any solid, liquid or gas is called its volume. The amount of matter in a solid, liquid or a gas is called its mass. The particles in matter are held together by pull forces (also known as forces of attraction) that exist between them. When a substance is cold, these pull forces hold it together as a solid. As it gets hotter, the particles start to wiggle; if it gets hot enough, the pull forces are broken. ## Arrangement of particles in solids, liquids, and gases | State of Matter | Arrangement of particles | Movement of particles | Shape | |---|---|---|---| | Solid | The pull forces are strong enough to hold the particles together in a tightly packed pattern. | Particles in a solid are tightly packed and they vibrate. | The shape of a solid remains the same in any container. | | Liquid | The particles are wiggling fast enough to slide past each other. However, they are still tightly packed. | Particles in a liquid are loosely packed and they can slide over each other. | The shape of a liquid changes according to the shape of the container. | | Gas | The particles are wiggling so fast that the pull forces can't keep them together. | Particles in a gas are very loosely packed and they can move freely. | A gas has no fixed shape and spreads to fill the entire container. If the container is not closed, the gas can escape. | | State of Matter | Volume | Particles in a solid always occupy the same amount of space in any container. Hence the volume of the solid remains the same. Example: A solid cube occupies the same amount of space in any container. | Particles in a liquid always occupy the same amount of space in any container. Hence the volume of the liquid remains the same. Example: 50 ml of a liquid always takes up 50 ml of space in any container. | Particles in a gas occupy all the space available to them in a closed container. Hence a gas has no fixed volume. Example: A gas can occupy the entire space in a container. | |---|---|---|---|---| | Solid | The particles in a solid always occupy the same amount of space in any container.| The particles in a liquid always occupy the same amount of space in any container. | The particles in a gas occupy all the space available to them in a closed container. | Identify the states of matter represented here and write them in the blanks provided. - Solid - Liquid - Gas ## Look Deep Use the sample response provided to complete the table given below. | Property of a solid, liquid, or gas | Write an example of an object with this property | Mention the state of matter of the object | Draw the arrangement of particles in the object | Explain the relationship between the arrangement of the particles and the property | |---|---|---|---|---| | Has definite shape and volume | A book | Solid | Diagram of tightly packed particles | Since the particles in the object are tightly packed, it has a definite shape and volume. | | Can be poured from one container to another | A glass of water | Liquid | Diagram of loosely packed particles | Since the particles in a liquid are loosely packed, they can flow easily from one container to another. | | Has no fixed shape or volume | A balloon | Gas | Diagram of very loosely packed particles | Since the particles in a gas are very loosely packed, they are able to fill the entire space of a container. | ## Changes in the State of Matter Different substances have different forces of attraction between their particles. This is why even at the same temperature, some things are solid, while other things are liquid, and other things are gas. Observe the given examples of changes in the state of matter. Discuss with your partner and determine the process involved in the change in each example. Write it in the blanks provided. You may refer to the help box if required. - **Freezing**: $l \to s$ on cooling - **Melting**: $s \to l$ on heating - **Condensation**: $g \to l$ on cooling - **Evaporation**: $l \to g$ on heating A change in state occurs when the particles in a solid, liquid or a gas are heated up or cooled down. - When we place water in the freezer, it cools down and loses heat energy. The molecules are moving slowly enough that the pull forces can hold them together as a solid. - When clothes are put out to dry, the molecules of water in the wet clothes absorb the heat in the air and gain energy. - This makes them wiggle around faster, so that the pull forces cannot hold them together, causing them to move farther apart and become a gas. - The image on the next page shows the relationship between energy and the behaviour of particles in the different states of matter. ## Think and Ink The first column of the table given below shows pictures depicting changes in the state of matter. Complete the table by: | Changes in the state of matter | Process involved | Behaviour of particles during the process | |---|---|---| | Water vapor in the air is condensing as water (dew drops) on the grass. | Condensation | Water vapor in the air condenses to dew drops on the grass. | | The boiling water in the vessel is evaporating into gas | Evaporation | Liquid molecules gain energy and overcome the pull forces between them, converting to gas particles | | The waterfall has frozen into solid ice | Solidification | Liquid particles lose energy and fall closer to each other, becoming tightly packed. | | The solid butter is into a liquid on the hot pancakes. | Melting | Solid particles gain energy and become loosely packed | ## Did You Know? There is a fourth state of matter, but it is very rare on planet Earth. It's called plasma: the superheated matter that stars like our Sun are made of. You can also find plasma in a lightning bolt or a neon light. Plasma may not be common on our planet, but there is a lot of it in outer space. In fact, because stars are so big, there is much more plasma in the universe than any other kind of matter! ## Companion Project Time - Summarise the properties of different states of matter. - Describe the behaviour of particles in different states of matter. - Explain the behaviour of particles using changes in the different states of matter. ## Smile with Science I don't believe anything that particles say. Why? Because they make up everything! ## Complete the Concept Map! - Melts - Evaporates - Solidifies - Condenses ## Glossary - **Atoms**: extremely tiny particles of matter - **Condensation**: the process in which gas changes into liquid on being cooled. - **Mass**: the amount of matter in a solid, liquid, or gas - **Matter**: anything that has mass and occupies space - **Molecules**: very tiny particles of matter - **Particle**: the smallest part of matter - **Volume**: the amount of space occupied by the particles in a solid, liquid, or gas ## Question Time **1. Fill in the blanks.** - The picture shows how particles are arranged in a _______. - When matter is in a solid state, the particles are held tightly together by the forces of ______. - The amount of space occupied by the particles in a solid, liquid or gas is called its _______. - The amount of matter in an object is called its ______. **2. True or False** - Particles of matter are called molecules or atoms. - A gas has the same volume, no matter which container it is in. - During the process of freezing, the particles of a liquid gain energy to become a solid. - The particles in a solid can be poured from one container to another. - Liquids take the shape of the container in which they are placed. **3. Match the following.** - Solid - Liquid - Gas - Occupies all the available space in a container - Has definite shape and volume - Can be poured from one container to another ## Answer in 5-6 sentences. 1. Describe the behaviour of particles that causes the formation of clouds. Include drawings. 2. Observe the picture. Explain the behaviour of particles that is causing the snowman to melt. What should happen to stop the snowman from melting? ## Answer the Following Question Complete the figure with the arrangement of particles in solids, liquids and gases in the respective boxes. Fill in the blanks with the names of the processes that cause the change in state among solid, liquid and gas. You can summarise the three states of matter however you complete the activities as per the instructions given.