"Matter And Their Parts" 4th Grade Science Test (Part 2) 2/9

Melting refers to the change of state from a solid to a liquid. It occurs when a solid substance is heated, causing the particles to gain enough energy to break free from their fixed positions and move more freely, forming a liquid. This process is commonly observed when ice melts to form water, or when a candle wax melts upon heating.

Water is unique in that it expands when it freezes. This is because of the hydrogen bonding between water molecules. When water freezes, the molecules arrange themselves in a hexagonal lattice structure, with each water molecule forming hydrogen bonds with four neighboring molecules. These hydrogen bonds create open spaces in the lattice, causing the water to expand and become less dense. This expansion is what allows ice to float on water and is also responsible for the cracking of pipes and containers when the water inside them freezes.

Chemical reactions involve the breaking and forming of chemical bonds. During this process, energy is either released or absorbed. This is known as the law of conservation of energy. Therefore, all chemical reactions either give off or use energy.

When bubbling or fizzing occurs, it indicates the release of a gas. This suggests that a chemical change has occurred. Chemical changes involve the formation or breaking of chemical bonds, resulting in the creation of new substances. In this case, the release of gas indicates that a chemical reaction has taken place, leading to the formation of the gas as a product.

Physical changes within water allow fish and other organisms to survive in a pond during winter. Water undergoes several physical changes during winter, such as freezing and forming ice. This process creates a layer of ice on the surface of the pond, which acts as insulation and prevents the water below from freezing completely. This allows fish and other organisms to survive in the relatively warmer water beneath the ice. Additionally, water has a high specific heat capacity, which means it can absorb and retain heat. This property helps regulate the temperature of the pond, providing a more stable environment for the organisms to survive.

Evaporation is the process in which a liquid changes into a gas without reaching its boiling point. This occurs when the molecules at the surface of the liquid gain enough energy to escape into the surrounding air. The escaping molecules create a cooling effect, which is why evaporation is commonly associated with the sensation of cooling. This process is different from boiling, as boiling requires the entire liquid to reach its boiling point and produce bubbles.

A chemical change refers to a process in which the starting materials (matter) undergo a transformation and result in the formation of different substances (another kind of matter). This change is typically accompanied by a chemical reaction, where the atoms of the original substances rearrange to form new compounds or molecules. Therefore, the given answer "chemical" accurately describes the type of change that occurs during a chemical reaction.

Fire is indeed a chemical reaction that produces light and heat. When a fuel source combines with oxygen in the presence of heat, combustion occurs, resulting in fire. During this process, the fuel molecules break down and recombine with oxygen molecules, releasing energy in the form of light and heat. This reaction is known as oxidation or combustion and is a fundamental characteristic of fire. Therefore, the statement "Fire is a chemical reaction that gives off light and heat" is correct.

When we cook food, it undergoes various chemical and physical changes that alter its color, taste, and texture. The application of heat during cooking causes proteins to denature, which affects the texture of the food. Additionally, cooking can also lead to the Maillard reaction, where amino acids and sugars react to produce browning and enhance the flavor of the food. Therefore, cooking is the process that brings about these changes in the color, taste, and texture of food.

Cooking and baking cause chemical changes in food. When food is exposed to heat during cooking or baking, chemical reactions occur that result in changes in the composition, flavor, and texture of the food. These chemical changes can include caramelization, Maillard browning, protein denaturation, and starch gelatinization, among others. These reactions transform the raw ingredients into a cooked or baked product, altering their chemical structure and creating new flavors and aromas.

When elements combine to form a compound, they undergo a chemical reaction that results in the formation of a new substance with different properties than the original elements. In the case of salt and chlorine, when they combine, they form sodium chloride, which is a compound with distinct properties from both the individual elements. Therefore, the statement that elements lose their original properties when they form a compound is correct.

A change of state refers to a physical change in which matter transitions from one state (solid, liquid, or gas) to another. This process involves the absorption or release of energy, such as melting, freezing, evaporation, or condensation. During a change of state, the arrangement and movement of particles within the substance are altered, resulting in a different physical form.

Reactions can cause the matter involved to become warm, hot, or even cold. This is because during a reaction, energy is either released or absorbed. When energy is released, it can manifest as heat, making the matter warm or hot. Conversely, when energy is absorbed, it can make the matter cold. Additionally, some reactions can also give off light as a result of the energy released. Therefore, reactions can have a range of effects on the temperature and light emission of the matter involved.

Boiling is the rapid change of state from a liquid to a gas. When a liquid is heated, its molecules gain energy and move faster. At the boiling point, the liquid's vapor pressure becomes equal to the atmospheric pressure, causing bubbles of gas to form throughout the liquid. These bubbles rise to the surface and escape into the air, resulting in the conversion of the liquid to a gas. Boiling is commonly observed when water reaches its boiling point and turns into steam.

Matter is composed of atoms, and atoms are made up of different elements. Elements are substances that cannot be broken down into simpler substances by chemical means. Therefore, most matter is made up of more than one element.

When two or more elements combine, they form a compound. This occurs during a chemical change, where the original substances undergo a transformation and create a new substance with different properties. Compounds are formed through chemical bonding, which involves the sharing or transfer of electrons between atoms. This process leads to the creation of a distinct substance with its own set of characteristics and properties. Therefore, the correct answer is "compound".

When enough energy is removed from a liquid, the particles within the liquid slow down and lose energy. This causes them to come closer together and form a more ordered arrangement, resulting in the formation of a solid. This process is known as freezing.

Boiling is a process where a liquid converts into a gas by the rapid formation of bubbles within the liquid. However, boiling is not the only way a liquid can become a gas. Evaporation is another common process where a liquid slowly converts into a gas at lower temperatures without the formation of bubbles. Other methods such as sublimation, where a solid directly converts into a gas without becoming a liquid, can also occur. Therefore, boiling is just one of the ways in which a liquid can transform into a gas.

Chemical changes can result in the production of gases. During a chemical reaction, the bonds between atoms are broken and new bonds are formed, resulting in the formation of different substances. In some cases, this can lead to the release of gas molecules as a byproduct. This can occur due to various reasons, such as the formation of gas bubbles or the release of gases from compounds involved in the reaction. Therefore, the correct answer is "gases".

Matter can exist in three forms: solid, liquid, and gas. Solids have a fixed shape and volume, with particles tightly packed together. Liquids have a definite volume but can change shape, with particles that are loosely packed and can move past one another. Gases have neither a fixed shape nor volume, with particles that are widely spaced and can move freely.

A change in color is the most visible sign of a chemical change because it indicates that the chemical composition of a substance has been altered. When a chemical reaction occurs, new substances are formed with different properties, including color. This change in color can be easily observed and is often used as an indicator of a chemical change taking place.

Chemical reactions have the potential to release heat, light, and electricity. During a chemical reaction, energy is often transferred or transformed, resulting in the production of these three forms of energy. Heat is generated due to the increase in temperature, light is emitted as a result of excited electrons returning to their ground state, and in some cases, electricity can be produced through the movement of charged particles.

You can tell whether a physical change has taken place by looking for a change in the size, position, and shape of the object. Physical changes involve alterations in the physical properties of a substance, such as its appearance or state, without changing its chemical composition. Changes in size, position, and shape indicate that the object has undergone a physical transformation, such as stretching, moving, or deforming. These changes can be observed visually or measured quantitatively to determine if a physical change has occurred.