SCI 7 T1 SUMMATIVE

What are Scientific Models? A scientific model is an abstract, conceptual, graphical, or physical representation of real-world phenomena. Models are employed to explain, predict, and understand the world and communicate scientific ideas. Models vary widely in form from tangible physical models like globes or anatomical figures to abstract conceptual models depicting energy flows in ecosystems. The evolution of scientific models reflects a journey from simple representations to complex and accurate depictions, driven by technological advances and expanding research findings. For example, the development of atomic models from simplistic early versions to today's detailed quantum mechanical models illustrates this progression. Science Scientific models serve multiple purposes across various branches of science. They simplify complex phenomena, enable predictions about future events or behaviors, facilitate hypothesis testing, and aid in teaching and communication. In medicine, models simulate drug effects on the human body, guiding new treatments. Environmental models predict climate change impacts, supporting policy and conservation. Here's how models serve specific purposes across four major branches of science:

Chemistry Models in chemistry help visualize molecular structures and reactions that are invisible to the naked eye. They allow chemists to predict the outcomes of chemical reactions and to understand the properties of substances at a molecular level.

Physics Physics models explain the fundamental forces and particles of the universe, describe motion and energy, and predict phenomena ranging from the microscopic to cosmic scales. They are essential for developing technologies and understanding the universe's laws.

Biology In biology, models are used to understand life at all levels, from molecular biology (like DNA structure) to ecosystems. They help in predicting biological responses and understanding complex interactions within living systems

Earth Science Earth science models explain geological processes, weather patterns, and climate change. They are crucial for disaster preparedness, resource management, and understanding Earth's past, present, and future.

Pure Substances Pure substances are the simplest forms of matter with a consistent composition and properties. They are the building blocks of the material world. There are two types of pure substances: elements and compounds. Elements, like the oxygen we breathe and the carbon in our pencils, are the basic units of matter that cannot be broken down into simpler substances by chemical means. For example, gold and oxygen are elements. It is represented in Figure 2 as blue particles that are all the same kind. 1.2. Basics of the Particle Model 7 Science 7 Unit 1: Understanding Particles in Matter Compounds, such as water (H2O) or table salt (NaCl), are made from two or more elements that are chemically bonded together. It is shown in Figure 2 as the gray and red balls connected to each other. Like how halo-halo is made up of mixed ingredients, but each ingredient, like the beans or the milk, is a pure substance because it is the same all the way through. Take a look at the three pure substances in Figure 3. Just bear in mind that an element is like a single singer, all alone with just one kind of atom. A compound is like a music band, with different atoms coming together to make something new and exciting. Figure 3. Examples of pure substances Figure 3a shows pure water. Water is very special because it is made of two hydrogen atoms and one oxygen atom. They come together like a team to make water. So, if we think about our music band, water is like a band because it is made up of different kinds of atoms. That means water is a compound! Next, Figure 3b shows oxygen, which we find in the air and tanks to help people breathe. Oxygen is made of two oxygen atoms. They are like twins because they are exactly the same kind of atom. Even though there are two atoms, they are the same, making oxygen an element. It is like a singer singing in harmony with their own echo. 1.2. Basics of the Particle Model 8 Science 7 Unit 1: Understanding Particles in Matter Lastly, Figure 3c shows salt made of sodium and chlorine atoms. These two different atoms join hands to make every grain of salt. Like water, salt is also a band of atoms playing together, so salt is a compound. In summary, Figure 3 shows examples of pure substances where water and salt are compounds, and oxygen is an element. Mixtures Mixtures are formed by physically combining pure substances. They can be categorized into two types: homogeneous and heterogeneous. Homogeneous mixtures are like a smoothie where all the ingredients are physically blended so well that you cannot tell them apart. Refer to Figure 2 again. It is just like the orange and green balls evenly distributed. Solutions are homogeneous mixtures composed of a solute and solvent. The solute is the dissolved substance and the solvent is the dissolving medium. Did You Know? Did you know that the air we breathe is a mixture of different gases, including oxygen, nitrogen, and carbon dioxide? It is a perfect example of a homogeneous mixture because it looks the same throughout. Heterogeneous mixtures are like a box of assorted chocolates; you can see the different types of chocolates, and they do not blend together into one uniform look. The delicious Filipino dish adobo is another example of a heterogeneous mixture because you can see and pick out the pieces of chicken, potatoes, and peppers. It is represented in Figure 2 as the balls not mixed uniformly. There are two kinds of heterogeneous mixtures: suspensions and colloids. In a suspension, particles are suspended in a liquid medium which can later settle in the bottom of the container, just like in children’s medicines. A colloid is a mixture in which one substance is dispersed or distributed to another substance, just like milk. 1.2. Basics of the Particle Model 9 Science 7 Unit 1: Understanding Particles in Matter Figure 4. Heterogenous vs. homogenous mixtures In Figure 4a, sand is poured into a glass of water. If you have ever played at the beach, you know that sand and water do not mix up completely. The sand will sink to the bottom; you can still see it there, separate from the water. This is what we call a heterogeneous mixture. It is a big word, but it just means you can see the different parts that make it up—they do not become invisible. Now, look at Figure 4b. Here, someone has stirred some sugar into a glass of water. When sugar is mixed with water, it dissolves, which means it seems to disappear, and you cannot see it anymore. But if you taste the water, it is sweet! That means the sugar is still there; it is just mixed in really well. This is a homogeneous mixture because everything is mixed up so well that it looks the same everywhere, even though we know the sugar is there.

Particles are incredibly tiny and are often visualized using models since they are too small to be seen with the naked eye. Their size can vary depending on the type of particle (e.g., atoms are smaller than molecules). The shape of particles can also differ; for example, water molecules have a bent shape, which affects how they interact with each other and with other substances. The dilution experiment, where dye or potassium permanganate is diluted in water, vividly shows that particles are extremely small and exist in vast numbers. Despite significant dilution, the color persists, suggesting the presence of countless tiny particles that maintain the solution's color. This experiment is a practical demonstration of the particle's size, illustrating that even a small volume of dye contains many dye particles. 1.3. Particle Movement and Characteristics 8 Science 7 Unit 1: Understanding Particles in Matter Figure 2. The image shows a dilution series of red dye, revealing that color remains even with significant dilution. This supports the idea that countless tiny particles exist in even a small amount of dye, demonstrating their minuscule size and abundance. Behavior of Particles Particles are always moving. The extent of their movement depends on their energy level, which is influenced by temperature. In warmer conditions, particles move faster because they have more energy. This movement is random and can involve vibration, rotation, and translation (moving from one place to another). The diffusion experiment highlights the continuous movement of particles. When a drop of dye is introduced into the water without stirring, it gradually spreads throughout the water. This diffusion process visually represents the random and constant motion of particles, driven by their inherent energy. The sugar in water experiment further illustrates particle behavior, demonstrating that particles move to occupy spaces between water molecules. This movement and interaction between particles are fundamental to understanding how substances mix and dissolve. 1.3. Particle Movement and Characteristics 9 Science 7 Unit 1: Understanding Particles in Matter Figure 3. Dye molecules spreading out in water, starting from a drop and eventually mixing evenly without stirring. This shows how tiny particles are always moving around, filling up space because they have energy to keep them going! Figure 4. Sugar particles are shown dispersing among water molecules when stirred, exemplifying how particles fill spaces between molecules and thus, demonstrating the dynamics of how substances dissolve and mix at the particle level. 1.3. Particle Movement and Characteristics 10 Science 7 Unit 1: Understanding Particles in Matter Interaction of Particles The way particles affect one another is crucial for understanding the properties of materials. Forces of attraction hold particles together, while forces of repulsion can push them apart. These interactions determine whether a substance will be solid, liquid, or gas under certain conditions. The forces of attraction between particles vary among solids, liquids, and gases, as demonstrated in the experiment comparing the effort required to change the shape of table (solid), water (liquid), and air (gas). This experiment underscores the concept that solid particles have strong forces of attraction keeping them closely packed in fixed positions, which makes solids retain their shape. Liquids have weaker forces of attraction, allowing them to flow and take the shape of their container, while gases have the weakest forces, enabling them to expand freely. The sugar in water experiment also touches upon interaction, showing how sugar particles integrate into the spaces between water molecules due to attractive forces, without significantly raising the water level. Figure 5. Solids hold shape with tight bonds, liquids adapt to container shapes with looser bonds, and gases fill spaces with very weak bonds. 1.3. Particle Movement and Characteristics 11 Science 7 Unit 1: Understanding Particles in Matter Effect of Temperature on Particles Let us talk about what happens when we play with temperature. Picture particles as tiny, super-energetic dancers. When the music (temperature) gets turned up, they dance faster and spread out more because they have more energy. But when the music slows down (temperature drops), they start to dance slower and come closer together because they are not as energetic. In our experiment, this explains why the balloon deflated in the cold water; the cold temperature made the particle-dancers slow down and huddle up, taking up less space. Then, when we moved the balloon to warm water, it was like turning up the music again. The particles got their energy back, danced faster, and spread out, making the balloon expand. This little experiment was our way of seeing how temperature changes affect how particles move and how much space they take up. Figure 6. In the experiment, the balloon deflates in cold water as particles slow and condense, and inflates in hot water as they energize and expand. 1.3. Particle Movement and Characteristics 12 Science 7 Unit 1: Understanding Particles in Matter Think about when you bake cookies or a cake. The heat from the oven gives energy to the particles in the dough or batter, making them move faster. This not only cooks the food but also causes it to rise if baking powder or soda is involved. The heat triggers a chemical reaction, producing gas that expands in the heat (those energetic particle dancers at work!), making your cake fluffy and delicious. It is like the oven is the DJ, turning up the heat to get those particle dancers moving and grooving in the mix. Our gadgets, like smartphones and computers, also dance to the tune of temperature changes. These devices generate heat when they are working hard. If they get too hot, the particles inside can move too energetically, causing the device to overheat and potentially damage. That is why many devices have built-in fans or heat sinks – to keep those particle dancers from getting too wild. It is a delicate balance, like keeping the dance floor cool enough for everyone to have a good time without overheating. Remember Temperature is a measure of how much energy particles have. The more energy they have, the faster they move. Relating Characteristics to the Particle Model of Matter Understanding the characteristics of particles is fundamental to grasping the particle model of matter. This key scientific concept explains the composition and behavior of all matter. This model is based on the idea that matter is made up of tiny, discrete particles that are always in motion and interact with each other in predictable ways. The experiments conducted, such as dilution, sugar in water, diffusion, observing forces of attraction, and effect of temperature, are practical demonstrations of how particles behave in different states and conditions. These observations reinforce the Particle Model by showing that particles are small, numerous, and in constant motion, with varying forces of attraction between them depending on whether they are in a solid, liquid, or gas state. The significance of the Particle Model lies in its ability to explain the physical properties of substances, the changes they undergo, and their 1.3. Particle Movement and Characteristics 13 Science 7 Unit 1: Understanding Particles in Matter interactions. For instance, why some materials conduct heat better than others, or why increasing temperature causes substances to change from solid to liquid to gas, can all be explained through the interactions and movements of particles as described by this model.

Particle Arrangement in Solids In solids, particles are tightly packed together in a fixed position, forming a rigid structure. This close-packed arrangement means that the particles are not free to move about but can only vibrate in place. Such a configuration gives solids their definite shape and volume. The strength of these vibrations increases with temperature, but the particles remain in their fixed positions, maintaining the solid's shape. In the warm-up activity, the first bond paper with cotton balls placed closely together with no spaces in between them represents the solid state. This model visually illustrates how particles in solids are closely packed, similar to the arrangement in traditional adobe bricks in the Philippines, where the closely packed particles provide strength and durability. Figure 2. The arrangement of particles in solid is tightly packed. 2.1. Visualizing Particle Arrangement in Different States 7 Science 7 Unit 2: How Particles Behave in Different States of Matter Vibration in solids is a subtle but crucial aspect. Despite their fixed positions, the particles in a solid vibrate because of the energy they contain. This vibration is more pronounced at higher temperatures, which is why solids expand when heated. The expansion of metal in the heat of the sun, a common occurrence in tropical climates like the Philippines, can be explained by the increased vibration of particles. The tactile experience of the warm-up activity, feeling the immobility of tightly packed cotton balls, reinforces the concept of particle vibration within a rigid structure. Particle Arrangement in Liquids Compared to solids, the particles in liquids have more freedom to move around. This freedom allows liquids to flow and take the shape of their container while maintaining a constant volume. The particles are still close, but they can slide past each other, enabling fluid movement. The flow of coconut oil at room temperature demonstrates this property, where the oil easily takes the shape of its container. The second bond paper in the warm-up activity, with cotton balls spread about 2 cm apart, simulates the liquid state. This model helps students visualize the relative freedom of movement that liquid particles enjoy, akin to flowing coconut oil. Figure 4. In liquids, particles remain closely packed but have the ability to slide past one another, offering greater movement freedom than in solids. 2.1. Visualizing Particle Arrangement in Different States 8 Science 7 Unit 2: How Particles Behave in Different States of Matter Clusters in liquids refer to the temporary groupings of particles. Despite their freedom of movement, liquid particles often form clusters that are held together for short periods before breaking apart and reforming. This behavior contributes to the liquid's viscosity, or its resistance to flow. Honey, with its high viscosity, shows this behavior distinctly, as its particles form longer-lasting clusters that make it flow slowly. The tactile exercise, with cotton balls slightly spaced, illustrates the fluid yet cohesive nature of liquids, enabling you to understand how liquid particles can move and form clusters. Particle Arrangement in Gases In gases, particles move freely and rapidly in all directions, far apart from each other. This arrangement allows gases to fill any container completely, regardless of its shape or size, and to spread out evenly. The significant distances between particles in gases account for their ability to be compressed and expanded easily. The smell of frying garlic spreading quickly throughout a Filipino kitchen is an example of gas particles moving freely and diffusing rapidly. The third bond paper in the warm-up activity, where cotton balls are scattered widely with at least 5 cm between each, visually and physically represents the gaseous state. This model illustrates the concept of free movement and significant spacing between gas particles, akin to the rapid diffusion of smells in a kitchen. Spacing between gas particles is much greater than in solids or liquids, which explains why gases are much less dense. This characteristic is evident in the way helium balloons float in the air; the helium gas inside the balloon is less dense than the surrounding air, allowing it to rise. The wide spacing between cotton balls in the warm-up activity's gas model vividly demonstrates the low density and high compressibility of gases, making the concept more tangible for students.

Understanding the mysteries of how substances change from one state to another—solid, liquid, and gas—is a fascinating journey into the world of science. These transformations, known as phase changes, are part of our everyday experiences, such as ice melting in our drinks and steam rising from a hot bowl of soup. Delving into these transformations allows us to grasp the remarkable interplay of energy and the organization of particles in everything around us. Let us embark on a discovery of phase changes, their energy dynamics, and their applications. 2.2. Understanding Changes of State 6 Science 7 Unit 2: How Particles Behave in Different States of Matter Demonstrations of Phase Changes Witnessing ice melt under the Sun, we observe a phase change from solid to liquid, termed melting or fusion. Boiling water shows a transformation from liquid to gas, known as vaporization or evaporation. These are not merely visual wonders; they involve significant energy exchanges. The transition from liquid back to solid is called freezing, and from gas to liquid is condensation. Another change, deposition, is the direct phase change from gas to solid without passing through the liquid phase. An example is when iodine gas turns back directly into its solid form on surfaces driven by a release of energy. Lastly, sublimation happens when a solid bypasses the liquid state and becomes gas, such as when mothballs shrink in closets, dry ice used in drinks evaporates, or solid air fresheners dissipate. Figure 2: Phase changes, including melting, freezing, vaporization, condensation, sublimation, and deposition 2.2. Understanding Changes of State 7 Science 7 Unit 2: How Particles Behave in Different States of Matter Energy changes accompany these phase changes. For instance, the forces between particles of matter weaken when the energy from the Sun is absorbed. This is observed when ice melts under the heat of the Sun. Conversely, when a less condensed state of matter is transformed to a more condensed state, such as the transformation of water vapor into dew, it releases energy into the surroundings. Remember Phase change: This is when matter changes from one state (solid, liquid, gas) to another, involving energy changes, like when ice melts to water or water boils to steam. Particle Arrangement During Phase Changes Particles rearrange as a material transforms from one state to another. For instance, when water boils, we see bubbles, which signals the transition to gas as molecules gain sufficient energy to break free from the liquid state. The energy required for these transitions influences how particles overcome the forces holding them together in a solid or liquid state. Figure 3. A pot of water reaching its boiling point, with bubbles rising to the surface as the water molecules transition from liquid to gas, capturing the energetic dance of particles during a phase change 2.2. Understanding Changes of State 8 Science 7 Unit 2: How Particles Behave in Different States of Matter In our kitchen, cooking rice demonstrates the energy needed for phase changes. The water absorbed by rice must boil, which absorbs heat from the surroundings. The heat absorbed allows the grains to expand and soften. Energy Changes During Phase Transitions The energy changes in phase transitions can be described as endothermic or exothermic. Endothermic processes, like melting ice, absorb energy, while exothermic processes, like freezing water into ice, release energy. These distinctions are practically applied in technologies like refrigeration, which uses the exothermic process of gas condensation to cool interiors. This is crucial for food preservation in the Philippines. Additional practical examples include the exothermic reaction of concrete curing. The process releases heat as it solidifies, which is crucial in construction. Another relevant significance of endothermic reactions is evaporative cooling, used by traditional palayok clay pots. This process keeps water cool by allowing water to seep through and evaporate. Figure 4. A temperature vs. heat energy graph showing endothermic and exothermic phase changes 2.2. Understanding Changes of State 9 Science 7 Unit 2: How Particles Behave in Different States of Matter Referring to the provided graph in Figure 4, we see that a solid absorbs energy as temperature increases until it reaches the melting point and becomes liquid—an endothermic reaction. Further heating turns the liquid into gas, another endothermic process. Conversely, cooling gas turns into liquid, and then further into solid. These processes are both exothermic reactions, where heat is released into the surroundings.