Chemistry Exam Review PDF

Chemistry Physical vs. Chemical Changes ​ Physical Change: A change where the substance remains the same but its appearance or state changes. ○​ Example: Melting ice. The water is still H₂O; it’s just a different state (solid to liquid). ​ Chemical Change: A proc...

Chemistry Physical vs. Chemical Changes ​ Physical Change: A change where the substance remains the same but its appearance or state changes. ○​ Example: Melting ice. The water is still H₂O; it’s just a different state (solid to liquid). ​ Chemical Change: A process where a new substance is formed with a different chemical composition. ○​ Example: Burning paper. It turns into ash and gases, creating a new substance. Evidence of a Chemical Change Look for clues like: ​ Change in color: A substance turns a different color during a reaction (e.g., rust forming on iron). ​ Formation of a gas: Bubbles or fizzing, indicating gas is produced (e.g., vinegar and baking soda). ​ Change in temperature: Some reactions release or absorb heat. ​ Change in smell: A new odor is often produced. Understanding Atoms and Neutrons ​ Atoms are the smallest units of elements, and they consist of protons, neutrons, and electrons. ​ To find the number of neutrons, subtract the atomic number (number of protons) from the atomic mass (round to the nearest whole number). ○​ Example: Zinc has an atomic number of 30 and an atomic mass of 65.​ Neutrons=65−30=35Neutrons=65−30=35. 1 Ionic vs. Molecular Compounds ​ Ionic Compounds: Formed between a metal and a non-metal, where electrons are transferred. ○​ Example: Sodium chloride (NaCl) is formed when sodium (Na) loses an electron, and chlorine (Cl) gains it. ​ Molecular Compounds: Formed between two non-metals, where electrons are shared. ○​ Example: Water (H₂O) is formed when hydrogen and oxygen share electrons. Naming Compounds ​ When naming ionic compounds, the metal comes first, followed by the non-metal with an "-ide" ending. ○​ Example: NaCl is sodium chloride. ​ For molecular compounds, use prefixes (mono-, di-, tri-) to indicate the number of atoms. ○​ Example: CO₂ is carbon dioxide. Writing Chemical Formulas ​ Write the symbol for each element and use subscripts to indicate the number of atoms. ○​ Example: In CaF2CaF2​, there is one calcium (Ca) and two fluorine (F) atoms. ​ If the compound contains a polyatomic ion (like nitrate NO3−NO3−​), keep the entire ion in parentheses if more than one is needed. ○​ Example: Magnesium nitrate is written as Mg(NO3)2Mg(NO3​)2​. Balancing Chemical Equations ​ Balancing means making sure there is the same number of atoms on both sides of the equation. 2  ○​ Example:​ Unbalanced:​ H2+O2→H2OH2​+O2​→H2​O​ Balanced:​ 2H2+O2→2H2O2H2​+O2​→2H2​O​ This ensures that there are 4 hydrogens and 2 oxygens on both sides. Classifying Reactions ​ Synthesis (Combination): Two or more reactants combine to form a single product. ○​ Example:​ A+B→ABA+B→AB​ (e.g., 2H2+O2→2H2O2H2​+O2​→2H2​O). ​ Decomposition: A single compound breaks down into two or more simpler substances. ○​ Example:​ AB→A+BAB→A+B​ (e.g., CaCO3→CaO+CO2CaCO3​→CaO+CO2​). ​ Single Displacement: One element replaces another in a compound. ○​ Example:​ AB+C→AC+BAB+C→AC+B​ (e.g., Zn+CuSO4→ZnSO4+CuZn+CuSO4​→ZnSO4​+Cu). ​ Double Displacement: Two compounds exchange ions to form new compounds. ○​ Example:​ AB+CD→AD+CBAB+CD→AD+CB​ (e.g., AgNO3+NaCl→AgCl+NaNO3AgNO3​+NaCl→AgCl+NaNO3​). ​ Combustion: A substance reacts with oxygen to produce energy (usually in the form of heat and light), and often carbon dioxide and water. ○​ Example:​ CH4+O2→CO2+H2OCH4​+O2​→CO2​+H2​O​ (Burning methane gas). 3 Understanding Reaction Types in Practical Examples ​ Word Equations: Describe the substances involved without using chemical formulas. ○​ Example: Aluminum reacts with zinc chloride to form zinc and aluminum chloride. ​ Word Equation: Aluminum + Zinc chloride → Zinc + Aluminum chloride. ​ Skeleton Equations: Show the chemical formulas without balancing. ○​ Example:​ Al+ZnCl2→Zn+AlCl3Al+ZnCl2​→Zn+AlCl3​. ​ Balanced Equations: Ensure the same number of atoms on both sides. ○​ Example:​ 2Al+3ZnCl2→3Zn+2AlCl32Al+3ZnCl2​→3Zn+2AlCl3​. Tips for Solving Chemistry Problems 1.​ Read the question carefully: Identify whether you need to name a compound, balance an equation, or describe a type of reaction. 2.​ Practice balancing equations: Start with simple reactions, then work your way up to more complex ones. 3.​ Understand the signs of chemical reactions: Look for color changes, gas bubbles, temperature changes, and new products. 4.​ Know the difference between physical and chemical changes: Physical changes don’t result in new substances, while chemical changes do. 5.​ Memorize common ions and their charges: Helps in predicting the chemical formula for ionic compounds. 6.​ Use diagrams: Bohr-Rutherford and Lewis Dot diagrams help visualize how atoms bond and how molecules are structured. Steps to Balance Chemical Equations 1.​ Write the Unbalanced Equation: ○​ Start by writing the skeleton equation where the reactants and products are written using their chemical formulas. ​ Example:H2+O2→H2OH2​+O2​→H2​O 4  2.​ Count the Number of Atoms of Each Element: ○​ Count how many atoms of each element are present on both sides (reactants and products). ​ For the example H2+O2→H2OH2​+O2​→H2​O: ​ On the left side: 2 hydrogen atoms and 2 oxygen atoms. ​ On the right side: 2 hydrogen atoms and 1 oxygen atom. 3.​ Balance the Atoms One Element at a Time: ○​ Start with elements that appear in only one compound on each side. Typically, balance the metals first, then non-metals, and finally oxygen and hydrogen. ○​ For example, balance the oxygen atoms in the equation: ​ To balance oxygen, add a coefficient of 1 for oxygen on the left side (already there) and adjust the hydrogen atoms on the right side. ​ Balanced equation:2H2+O2→2H2O2H2​+O2​→2H2​O ​ Now, both sides have 4 hydrogen atoms and 2 oxygen atoms. 4.​ Check the Balance of All Elements: ○​ Ensure that the number of atoms of each element is the same on both sides. ​ In the example: ​ Left side: 4 hydrogen atoms, 2 oxygen atoms. ​ Right side: 4 hydrogen atoms, 2 oxygen atoms. ​ The equation is now balanced. 5.​ Verify the Final Equation: ○​ Double-check all elements to make sure the equation is fully balanced. ○​ Example:2H2+O2→2H2O2H2​+O2​→2H2​O ○​ Both sides have 4 hydrogen atoms and 2 oxygen atoms, so it is balanced. Common Tips for Balancing Equations ​ Balance Oxygen and Hydrogen Last: These elements are often in multiple compounds (especially water), so balancing them first can make it more difficult. 5  ​ Use Coefficients: Do not change the subscripts in the formulas (e.g., H₂O should stay H₂O, not H₂O₂). Adjust the number of molecules by adding coefficients in front of compounds. ​ Start with Complex Molecules: Begin by balancing molecules that are most complex, then move to simpler ones. ​ Fractional Coefficients: If you end up with a fractional coefficient (e.g., 1/2), multiply the entire equation by the denominator to clear the fraction. Examples of Balancing Chemical Equations Example 1: Combustion of Propane Unbalanced Equation: C3H8+O2→CO2+H2OC3​H8​+O2​→CO2​+H2​O Steps: 1.​ Count atoms: ○​ Left side: 3 carbon (C), 8 hydrogen (H), 2 oxygen (O). ○​ Right side: 1 carbon (C) in CO₂, 2 hydrogen (H) in H₂O, and oxygen (O). 2.​ Balance carbon atoms: ○​ Add a coefficient of 3 to CO₂:C3H8+O2→3CO2+H2OC3​H8​+O2​→3CO2​+H2​O 3.​ Balance hydrogen atoms: ○​ Add a coefficient of 4 to H₂O:C3H8+O2→3CO2+4H2OC3​H8​+O2​→3CO2​+4H2​O 4.​ Balance oxygen atoms: ○​ Oxygen on the right side: 6 from CO₂ + 4 from H₂O = 10. ○​ To balance, add a coefficient of 5 to O₂:C3H8+5O2→3CO2+4H2OC3​H8​+5O2​→3CO2​+4H2​O Final Balanced Equation: C3H8+5O2→3CO2+4H2OC3​H8​+5O2​→3CO2​+4H2​O 6 Example 2: Double Displacement Reaction Unbalanced Equation: AgNO3+NaCl→AgCl+NaNO3AgNO3​+NaCl→AgCl+NaNO3​ Steps: 1.​ Count atoms: ○​ Left side: 1 silver (Ag), 1 nitrate (NO₃), 1 sodium (Na), 1 chloride (Cl). ○​ Right side: 1 silver (Ag), 1 chloride (Cl), 1 sodium (Na), 1 nitrate (NO₃). 2.​ All atoms are already balanced. Final Balanced Equation: AgNO3+NaCl→AgCl+NaNO3AgNO3​+NaCl→AgCl+NaNO3​ Example 3: Decomposition of Calcium Carbonate Unbalanced Equation: CaCO3→CaO+CO2CaCO3​→CaO+CO2​ Steps: 1.​ Count atoms: ○​ Left side: 1 calcium (Ca), 1 carbon (C), 3 oxygens (O). ○​ Right side: 1 calcium (Ca), 1 carbon (C), 2 oxygens (O) in CaO and 2 oxygens (O) in CO₂. 2.​ Balance oxygen atoms by ensuring the total on both sides is equal. Final Balanced Equation: CaCO3→CaO+CO2CaCO3​→CaO+CO2​ The equation is balanced as is. 7  Biology 1. Identify the function of each of the following organelles: ​ Nucleus:​ Function: The cell's control center. It houses the cell's DNA, which carries the instructions for all cellular activities, including growth, metabolism, and reproduction. ​ Mitochondria:​ Function: The cell's energy maker. Mitochondria generate energy in the form of ATP through cellular respiration, which powers various cell processes. ​ Cell wall:​ Function: The plant cell's protector. It provides structure, support, and protection for the cell. The cell wall is rigid and made mostly of cellulose in plant cells. ​ Cytoplasm:​ Function: The cell's inner gel. It is a jelly-like substance that surrounds the organelles, providing a medium for chemical reactions and supporting the cell's structure. ​ Chloroplast:​ Function: The plant's food maker. Chloroplasts contain chlorophyll, which captures sunlight for photosynthesis, converting light energy into chemical energy stored in glucose. ​ Vacuole:​ Function: The cell's storage space. Vacuoles store nutrients, waste products, and help maintain turgor pressure in plant cells (keeping the cell rigid). 2. What are the 3 parts of the cell theory? ​ a) All living things are made of cells. ​ b) The cell is the basic unit of structure and function in living organisms. ​ c) All cells arise from pre-existing cells. 8 3. Which organelles are in plant cells and not animal cells? ​ Cell Wall: Provides structural support and protection (not in animal cells). ​ Chloroplasts: Contain chlorophyll for photosynthesis (not in animal cells). ​ Vacuoles: Larger and central in plant cells, they store water, nutrients, and waste products. 4. Label the diagram of the human digestive system. Identify the 4 stages and where they occur. ​ Ingestion: The intake of food through the mouth. ​ Digestion: The breakdown of food into smaller molecules by mechanical (chewing) and chemical (enzymes) processes in the mouth, stomach, and small intestine. ​ Absorption: Nutrients from digested food are absorbed into the bloodstream through the walls of the small intestine. ​ Elimination: The removal of undigested food and waste products through the rectum and anus. 5. Labelling the following terms #1-4 in the correct order of food processing: 1.​ Ingestion 2.​ Digestion 3.​ Absorption 4.​ Elimination 6. What does the small intestine primarily absorb? The small intestine primarily absorbs nutrients from digested food, including sugars, amino acids, fatty acids, and vitamins. These nutrients are absorbed into the bloodstream via villi in the lining of the small intestine. 9 7. What does the large intestine primarily absorb? The large intestine primarily absorbs water and minerals (such as sodium and potassium). It also absorbs some remaining nutrients and stores waste material until elimination. 8. Draw the phases of mitosis, and explain what is happening during each phase: ​ Prophase: ○​ The chromosomes condense and become visible. The nuclear membrane begins to break down, and the spindle fibers form. ​ Metaphase: ○​ Chromosomes line up along the middle (metaphase plate) of the cell, attached to spindle fibers. ​ Anaphase: ○​ Sister chromatids are pulled apart towards opposite poles of the cell by the spindle fibers. ​ Telophase: ○​ The nuclear membranes re-form around the separated chromosomes, and the chromosomes begin to de-condense back into chromatin. ​ Cytokinesis (final step): ○​ The cytoplasm divides, resulting in two daughter cells. 9. Label the diagram of the human respiratory system. Label parts such as: ​ Nose: Filters, warms, and moistens air. ​ Trachea: The windpipe that carries air to the bronchi. ​ Bronchi: Tubes that carry air into each lung. 10  ​ Bronchioles: Smaller branches of the bronchi in the lungs. ​ Alveoli: Tiny air sacs where gas exchange occurs. 10. Where do the respiratory system and the circulatory system (capillaries) interact for gas exchange? The respiratory system and circulatory system interact in the alveoli of the lungs, where oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli to be exhaled. 11. **Veins take blood ______________ the heart. Arteries take blood ______________ the heart.** ​ Veins: Take blood to the heart. ​ Arteries: Take blood away from the heart. 12. What makes a cancer cell different from a normal cell? What is a tumor? ​ Cancer cells: These cells divide uncontrollably and do not respond to normal regulatory signals that stop cell division. They can invade other tissues (metastasis) and form tumors. ​ Tumor: A mass of abnormal cells. It can be benign (non-cancerous) or malignant (cancerous). 13. What is a stem cell? 11 A stem cell is a type of cell that has the ability to develop into different types of cells in the body. They are unspecializedand can divide to produce more stem cells or differentiate into specialized cells (like muscle cells, blood cells, or nerve cells). ​ Totipotent stem cells: Can develop into any cell type in the body. ​ Pluripotent stem cells: Can develop into almost any cell type, but not the entire organism. ​ Multipotent stem cells: Can develop into a limited range of cell types. Optics 1. Refraction, Opaque, Transparent, Translucent ​ Refraction:​ Refraction occurs when light travels from one medium to another, causing it to change direction. This happens because light travels at different speeds in different materials. For example, when light moves from air (less dense) into water (denser), the light slows down and bends toward the normal (an imaginary line perpendicular to the surface). Similarly, when light moves from water to air, it speeds up and bends away from the normal.​ Example: If you place a pencil in a glass of water, the pencil will appear bent at the water’s surface due to refraction. ​ Opaque:​ Opaque objects do not allow light to pass through them. Instead, light is either absorbed or reflected by the surface. An opaque material will create a shadow because it blocks the passage of light completely.​ Example: A wooden block is opaque because no light can pass through it. ​ Transparent:​ Transparent materials allow light to pass through them without significant scattering or absorption, so you can see objects clearly through them. The light passes straight through without changing direction significantly.​ Example: A clear glass window is transparent because it allows light to pass through without distortion. 12  ​ Translucent:​ Translucent materials allow light to pass through but scatter it in many directions, which causes objects behind them to appear blurry or unclear.​ Example: Frosted glass is translucent because light passes through but is scattered, making objects behind it difficult to see clearly. 2. Matching Terms in a Diagram (Reflection) When you are asked to match terms like incident ray, reflected ray, angle of incidence, and normal in a diagram, you need to understand their definitions: ​ Incident Ray: This is the light ray that strikes the surface. ​ Reflected Ray: This is the ray that bounces off the surface after it hits it. ​ Normal: The normal is an imaginary line that is perpendicular (at a 90-degree angle) to the surface at the point where the incident ray strikes. ​ Angle of Incidence: This is the angle between the incident ray and the normal. ​ Angle of Reflection: This is the angle between the reflected ray and the normal. The law of reflection states that the angle of incidence equals the angle of reflection. 3. Calculating Angles of Reflection and Incidence Refraction follows a principle where the angle of incidence equals the angle of reflection. So, if you are given the angle of incidence (say 52 degrees), the angle of reflection will also be 52 degrees. This principle is known as the Law of Reflection. 4. Image Formation in Concave and Convex Mirrors To draw the image formed by a concave or convex mirror, you need to understand where the object is in relation to the focal point of the mirror: 13  ​ Concave Mirror: A concave mirror is curved inward, like the inside of a bowl. The position of the object determines the nature of the image: ○​ If the object is beyond the focal point, the image will be real, inverted, and reduced in size. ○​ If the object is between the focal point and the mirror, the image will be virtual, upright, and magnified. ​ Example: If you hold an object close to a concave mirror, the image will appear upright and larger than the object itself. ​ Convex Mirror: A convex mirror is curved outward. This mirror always forms a virtual, upright, and reduced image regardless of the object’s position.​ Example: Convex mirrors are used in car side mirrors because they give a wide field of view and the image is always reduced. 5. SALT (Size, Attitude, Location, Type) of Images The SALT method is used to describe images formed by mirrors or lenses: ​ S (Size): Is the image larger, smaller, or the same size as the object? ​ A (Attitude): Is the image upright or inverted? ​ L (Location): Is the image formed in front of or behind the mirror (or lens)? ​ T (Type): Is the image real or virtual? For instance, in a concave mirror when the object is placed beyond the focal point: ​ S: Smaller ​ A: Inverted ​ L: In front of the mirror (real image) ​ T: Real 6. Concave vs. Convex Mirrors ​ Concave Mirror:​ A concave mirror is curved inward, like the inside of a spoon. The shape focuses light to a single point called the focal point. These mirrors can form 14  both real and virtual images depending on where the object is placed. Concave mirrors are used in applications like makeup mirrors or telescopes where magnified, real images are needed. ​ Convex Mirror:​ A convex mirror bulges outward. It diverges light rays, meaning the reflected rays spread apart. The image formed is always virtual, smaller, and upright. Convex mirrors are commonly used for security and safety purposes, such as in car side mirrors. 7. Types of Light Sources ​ Chemiluminescence:​ The emission of light resulting from a chemical reaction without producing heat. An example is a glow stick, where chemicals mix and release light. ​ Bioluminescence:​ Light produced by living organisms through biochemical reactions. Fireflies and some types of fish (like jellyfish) emit light through a chemical process that occurs in their bodies. ​ Incandescence:​ The emission of light from a hot object. When an object like a metal filament in a light bulb is heated to a high temperature, it glows. This is a traditional method of producing light but is less energy-efficient compared to newer methods like LEDs. ​ Fluorescence:​ A material absorbs light at one wavelength and then re-emits it at a longer wavelength. Fluorescent lamps are common examples of this phenomenon. The light emitted is visible and often more intense than the original absorbed light. 8. Wavelengths of Visible Light ​ Longest wavelength: Red light has the longest wavelength in the visible spectrum. ​ Shortest wavelength: Violet light has the shortest wavelength in the visible spectrum. 15 Wavelengths are important in determining the energy of light. The longer the wavelength, the lower the energy. Conversely, the shorter the wavelength, the higher the energy. 9. Reflection of Light on a Blue Film When white light (which contains all colors) shines on a blue film: ​ Reflected color: The blue light is reflected because the film selectively reflects blue wavelengths of light. ​ Absorbed colors: All other colors (red, green, yellow, etc.) are absorbed by the blue film. This selective reflection and absorption explain why we see the blue color on the film. 10. Electromagnetic Spectrum (From Strongest to Weakest) The electromagnetic spectrum is ordered based on the energy of different types of electromagnetic radiation. From strongest (highest energy, shortest wavelength) to weakest (lowest energy, longest wavelength): 1.​ Gamma rays 2.​ X-rays 3.​ Blue light 4.​ Red light 5.​ Infrared 6.​ Radio waves Gamma rays have the highest energy and shortest wavelength, while radio waves have the lowest energy and longest wavelength. 16 11. Refraction with a Straw in Water When a straw is placed in water, it appears bent or disconnected at the water's surface. This happens due to refraction, the bending of light as it moves from one medium (water) to another (air). The light slows down in the water, causing it to bend at the water-air interface. This bending distorts the appearance of the straw. Earth and space global warming Global warming: The long-term increase in Earth's average surface temperature, primarily due to the accumulation of greenhouse gases in the atmosphere caused by human activities like burning fossil fuels and deforestation. What is climate change? ​ Climate change: Broad changes in global or regional climate patterns, including temperature, precipitation, and wind. It encompasses global warming but also includes changes like rising sea levels, more extreme weather events, and shifts in ecosystems. What is the Greenhouse Effect ​ The Greenhouse Effect is a natural process where greenhouse gases in Earth's atmosphere trap heat from the sun, keeping the planet warm enough to sustain life. ​ Enhanced Greenhouse Effect: An increase in greenhouse gas concentrations due to human activities, leading to excess heat being trapped and contributing to global warming. three of the main greenhouse gases created by man? 1.​ Carbon dioxide (CO₂): Released by burning fossil fuels like coal, oil, and natural gas. 17 2.​ Methane (CH₄): Emitted from livestock digestion, rice paddies, and landfills. 3.​ Nitrous oxide (N₂O): Released from agricultural activities, especially fertilizer use, and industrial processes. 18