Chapter 5: Properties of Matter

Lesson 1: Describing Matter Lesson 2: Measurement Lesson 3: Classifying Matter

Lesson 1: Describing Matter

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Matter is anything that has mass and occupies space. your pencil, your snack, the water inside your water bottle, the bircks used to make your classroom, the juice inside the juicebox... all these things are made of matter. However, light, heat and sound are not matter, because they dont occupy space.

We can describe matter using its properties. A property is a characteristic that you can observe for example, color, shape, size etc are some of the characteristics.

Mass: mass describes the amount of matter in an object. You can measure mass using grams (g) or kilograms (kgs). Mass is measured using a tool called A balance. A balance measures the mass by comparing the object to another object of known mass.

Volume: volume is a measure of how much space and object occupies.

Bouyancy: When you put an object in wter, you feel it being pushed upwards. For example, if you try to push a baloon or abeach ball inside a swimming pool, you will feel the water pushing the ball out. The upward force ofa liquid or gas is called bouyancy. It is the force tht enables objects to float on water and is used to design boats and ships.

States of Matter

Matter can be found in three common states namely: solids, liquids and gases.

Solids: Solids have a shape and take up a definite amount of space. In solids, the particles of matter are packed tightly and mostly in a regular pattern. The pencil, pen, book, desk, blocks, wood, ice ... are all solids.

Liquids: Liquids do not have a definite shape, they take the shape of the container. Juice is a liquid, if you pour it into a glass, it will spread out and take up the shape of the glass. In liquids, the particles that make up matter are further apart and can move more freely than in solids. Water, juice, milk, and oil are examples of liquids.

Gases: If you pour juice into a glass, it goes to the bottom of the glass makes the glass half full. Gases do not have a definite shape. In addition, if you put a gas into a container, it spreads out throughout the container. In gases, the particles spread out so as to fill the space in the container. If the space is small, the particles will be tight together, if the space is big, the particles will be spread out further apart. Air is mostly made out of gases.

Lesson 2: Measurement

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Measuring is one way to determine the size of an object, and to compare it with the size of another object. For this to be successful, we need to use the same units of measurement so that different people can understand what the measurement actually means. These units that people agree on are called standard units. Scientists use the metric system which uses prefixes like milli-, centi -, and kilo- . The metric system is based on units of ten to move from one prefix to the next. For example, 1 centimeter is made up of 10 millimeters. 1 meter is made up of 100 centimeters, and 1 kilometer is made up of 1000 meters.

Length: Length is the measure from one end to the other end. It is usually the measure of the long side of a 2D shape. For example, if you place your book on the desk, the length is the measure of the long side of the book.

Width: Width is the measure of how wide an object is. It corresponds to the shorter side of a 2D shape.

Area: Area describes the number of unit squares that an object's surface covers. An easy way to calculate the area of a rectangle is to multiply the Length (L) and the Width (W). Therefore, A = L X W. If the length is 15 centimeters (cm) and the width is 10 cm, the Area is = 15 cm X 10cm = 150 cm². cm² is read as 'square cm. When we express Area as A = L X W, we call this a formula. So the formula to calculate the area (A) of a rectangle is L X W. This formula remains the same if we are calculating the area of a square. However, because the square has equal sides, the measure of L will be equal to the measure of W, so even if you switch L and W, you still get the same correct answer. A square with sides equal to 10 cm has an area of L X W = 10cm X 10cm = 100 cm²

Volume: Volume describes the number of cubes that can fit inside an object. It is a measure of how much space an object occupies. Therefore the object needs to have a 3 dimensional structure. Here, we introduce the concept of height (H). If you are measuring the volume of an ice cube that measures 2cm on all sides, the volume is; V = L X W X H = 2cm X 2cm X 2cm = 8 cm ³. Realise that the formula to calculate the volume of an object can be shortened to V = A (of the base) X H or short V = Base X height. This is important because the same formula applies if the object is based on rectangular sides or if the base is of a different shape. A 3D shape with a circular base is called a cylinder.

To find the volume of an irregularly shaped object, you can use water in a measuring container. First add the water, measure how much water is in the container. Then surmerge the object until it has all been covered by the water then record the new reading of the volume of water. The volume of the object is the difference between the new final reading and the original reading. This is called displacement. A solid object will displace an amount of water that is the same as its own volume.

Density: Density is the amount of matter per unit space (volume). Remember we said solids have particles that are tightly packed and gases have particles that are far apart, this corresponds with how much matter is in a unit volume, so solids are expected to have more matter per unit volume than gases. This also means solids are expected to have a higher density than liquids, and liquids have a higher density than gases. in addition to this, objects of the same state can have different densities. As in, different solids can have different densities. The amount of matter is measured using Mass and is expressed in grams (g). To calculate the density of an object, divide its mass by its volume, M ÷ V. If the mass is in grams and the volume in cubic centimeters, then the result will have units in grams per cubic centimeter (g/cm³).

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Density and Bouyancy: Remember, bouyancy is the upward force of a liquid or gas on another object. It determines if an object will sink or float in the liquid, such as water. An object floats if the its density is lower than the density of the liquid. For example, the Density of water is 1g/cm³. The density of cork is 0.24g/cm³. Will cork float or sink? Cork will float, because water has a higher density than cork. Brass has a density of 8.5g/cm³. Will brass float or sink in water?
Liquids can also float on top of water as you observe when you add oil into water.

You can change the density of an substance by either heating it or cooling it. Heating makes the particles move faster, making the particles move further apart and this reduces the object's density. This is the reason a hot air balloon will rise up in the air because the air inside the balloon is heated, making it less dense than the air outside the balloon.

Weight: Weight measures the amount of gravitational pull between an object and a planet, in this case, earth. Gravity is a force, or a pull, acting between two objects. The force of gravity acting on an object depends on the object's mass. The higher the mass, the higher the weight. However, the gravitational force also changes, like if you go to a different planet or the moon, so the higher the gravitational force, the higher the weight. The standard metric unit for weight is the Newton (N). Different countries use different units to measure weight, like Pounds (lb) is the US. An object with a mass of 1kg weighs 9.8 Newtons on earth and only about 1.6 Newtons on the moon.

Lesson 3: Classifying Matter

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Many years ago, people thought that all matter was made up of either Earth, Water, Air and Fire. We now know that matter is made up of elements. An element is a substance that is made up of only type of matter. Because an element is made of one type of matter, you cannot break it down into any simpler form. Hydrogen, Oxygen, Gold, Silver are some examples of elements. There are several other examples of elements.

Atoms: An atom is the smallest part of an element. You can think of atoms as particles. However, atoms are very tiny and you cannot see them with your naked eye. All atoms in an element are alike, for example, all atoms in silver are alike, and you can describe them as Silver atoms. Same for hydrogen and gold and other elements. The atoms of a certain elemet are different from the atoms of another element.

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Metals and Nonmetals: A metal is shiny, it can be bent or hammered into shape. examples of metals include Iron, Aluminum and Copper. Metals allow heat and electricity pass through them (i.e., they conduct heat and electricity). Thats why Aluminum and Iron are used for cooking pots and Copper is used for Electric wires.

Metalloids are elements that have some of the properties of metals but not all.

Nonmetals is a large group of elements euch as Nitrogen and Hydrogen (and many others). They have none of the properties of metals.

Element Symbols: Most elements can be represented using symbols. In most cases, the symbol is the first letter of the element's name, such as Hydrogen - H, Nitrogen - N, Oxygen - O, Carbon- C and so forth. In other cases, the element's symbol is obtined from the element's latin name. For example, Gold is called aurum in latin, and the symbol for gold is Au.

Periodic Table: Because of the diverse differences between elements, scientists found it necessary to develop a way to organize the elements, so that elements with similar properties can be grouped together. About 150 years ago, a scientist named Mendelev developed a Periodic Table a s way to organize elements. See the periodic table below:

Columns and Rows: As shown on the periodic table, elements are organized into rows and columns. Elements in the same column are said to be in the same Group. Elements in the same row are said to be in the same Period. When Mendeleev arranged the elements in a table, he saw a pattern. Elements with similar properties were grouped near one another. Scientists use these patterns to predict how an element behaves. Hydrogen (H), for instance, reacts easily with other substances. The elements that share its column in the periodic table also react easily. Elements that share the same row often have similar properties, too. Iron (Fe) is magnetic. Find Iron in the Periodic table. Notice that the two elements next to iron are also magnetic.

Chapter 6: Changes in Matter

Lesson 1: How Matter Can Change Lesson 2: Mixtures Lesson 3: Compounds Lesson 4: Thermal Energy

Lesson 1: How Matter Can Change

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We can classify changes into two types; either Physical change, or Chemical change. A physical change is when matter changes in form, state, shape etc but remains the same substance. If you mold clay to make a flower pot, you have changed the shape of the clay but it still remains clay. If you take an ice cube from the freezer and allow it to melt into water, you have changed its state but it still remains water. Ice was just frozen water. These kids of changes are called Physical Changes. Physical changes involve a change in size, shape, structure, state and even position/location.

If you heat a solid substance, the particles move faster and if there is enough energy, the solid will melt into a liquid. Melting is the change of state from solid to liquid. If you heat the liquid further, the particles move even further apart and the liquid changes to a gas. This process is called Boiling. Liquids can also change to gases without necessarily undergoing boiling. Evaporation is that process where a liquid can change to a gas without boiling. Water on ponds, lakes, rivers and oceans is constantly undergoing evaporation.

Cooling occurs when we take away heat energy from a substance. This makes the particles move closer together. If we cool a gas into a liquid, we call that Condensation. Or we can say the gas condenses to a liquid. If we cool a liquid into a solid (like if we put water into the freezer), we call that Freezing, or we can say the liquid freezes into a solid. Water freezes into ice.

A chemical change results in a change in the type of matter present in the object. The resulting substance has different properties from the original matter. If ou leave you bicycle out in the rain throughout summer, it will begin to rust. Rust is a chemical change that occurs on Iron when it is exposed to water and air (oxygen). It appears brown in color and in this case, you cannot reverse the rust beck to iron. Some chemical reactions can be reversed so that you obtain the original substance(s). Most chemical reactions either use up energy, or produce energy. The energy may be in form of heat, light or electricity.

There are very many chemical changes. Here are a few examples:

• Cooking: cooking and baking results in chemical changes on the ingedients.
• When you mix vinegar and baking soda, you see bubbles being released. These bubbles are actually Carbon Dioxide gas being released by the chemical reaction between vinegar and the baking soda.
• Burning paper or wood or other materials also causes chemical changes. The smoke released in a mixture of carbon dioxide, moisture and soot particles. (There are other products too that you dont need to know at this level).
• Rusting

How do you know a chemical change has occured?

There are some tell tale signs that you can use to detect if a chemical reaction has occured. For instance:

• Change in color
• Release of gas
• Smell
• Change in temperature - the substance could either become warmer or colder.
• Sometimes chemical reactions result in production of energy such as light. Fire is good example here.

Lesson 2: Mixtures

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A mixture (as you probably already guessed) is a combination of two or more kinds of matter. However, in a mixture, each kind of matter keeps its properties. For example, a salad is a mixture of various vegetables and dressing. But each vegetable remains in its original state.

When two substances are mixed together and they blend completely so you can no longer detect the individual substances, we call this a Solution.

A mixture of two metals (or a mixture that contains at least one metal) is called an Alloy. Some alloys are stronger than the elements used to make it. Bronze is an alloy or Copper and Tin, and it is stronger than either of them. Steel is an alloy or Iron and carbon.

Mixtures can be separated using various methods. For example, you can allow the substances to settle. Settling is when the matter with a higher density moves down to the bottom of the container and the matter with the lower density stays at the top. If you add sand into water, the sand will settle at the bottom.

Filtration is a method to separate mixtures based on size. You can filter water using a sieve, the larger particles stay in the sieve and the smaller particles pass through the sieve and are collected as filtrate.

Magnetic attraction: Magnets are often used to separate scrap metal in a junk yard. A magnet will attract elements such as iron, nickel and cobalt.

One method to separate substances in a solution is to use distillation. Distillation relies on boiling points. In distillation, a solution is heated until the liquid that has a lower boiling point becomes a gas. The solid or the liquid that has a higher boiling point is left behind. The gas is passed slowly through a tube where it slowly cools down (condenses) and goes back to a liquid state and settles in another tube. This is the method used to separate gasoline fro curde oil.

Evaporation can also be used to separate a solution into its its parts. This is the process used to make salt from sea water. When you allow sea water to evaporate, you are left with solid salt. This technique differs from distillation in that; 1. it doesnt involve boiling, 2, we are aiming to collect the solid, and we allow the water to be lost into the air.

Lesson 3: Compounds

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Remember we said chemical changes are changes that result in a new product that is different from the original substances. A Compound is formed when two or more elements combine chemically. Iron is a gray metal. Oxygen is a colorless / clear gas. Water is also clear/colorless. When Iron reacts with Oxygen, in the presence of moisture, to form Rust, it changes color to a brown solid.

Here are a few examples of compounds.

• Water (liquid) - combination of Hydrogen (gas) and Oxygen (gas)
• Table salt (solid) - combination of Sodium (Na) (solid) and Chlorine (Cl) (gas).
• Rust (solid) - combination of Iron (Fe) (solid) and Oxygen (O) (gas) in the presence of water/moisture.
• Sugar, starch, glucose are all compounds of Carbon, Hydrogen and Oxygen (C H O) with each element in different proportions to make the different compounds.

Acids: An acid is a substance that turns blue litmus paper red. Acids are sour in taste. Citric acid is what gives lemons a sour taste. Strong acids can be very harmful, children should stay away from acids because they can burn your skin.

Bases: Bases are substances that can turn red litmus paper blue. They taste bitter. A strong base can be harmful. Such as drain cleaners. Children should not taste any substance that may contain a strong base.

Water does not change the color of litmus papers. Water is neither an acid nor a base.

Lesson 4: Thermal Energy

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Thermal energy is one type of energy. There are several other types of energy that you will learn about soon. Thermal energy is the energy of moving particles of matter. Heat is the flow of thermal energy from one object to another. Thermal energy always moves from warmer objects to cooler objects. Objects feel hot because the thermal energy has moved from the object to your hand.

Heating an object means you subject an object to thermal energy and by doing so, you increase the thermal energy of the object making it hot. This change involves increasing the movement of the particles that make up the object. This change results in the particles moving further apart from each other, which results in Expansion. Expansion is the apparent or subtle increase in the size of an object due to heating. The change in thermal energy can be detected as a change in Temperature. remember we meausre an object's temperature using a Thermometer. In fact, you can see the word thermometer has the 'thermal' sound in it. A meter that measures thermal energy (thermo-meter).

Most thermometers use alcohol (colorised red) or mercury (appears like a silver color) in a very thin tube. As the thermometer warms, the alcohol or mercury also warms and begins to expand, which results in it rising up the narrow tube. The mercury or alcohol will rise to the point that corresponds to how warm the surface was and this can be read on the scale. The scales can either be in degrees celsius (^oC) or degrees Fahrenheit (^oF).

You have already noticed by now that water is used a reference in many situations. (see the topic on density where the density of water is 1g/cm³ as a way to create easy comparison with other substances. ) In this case, the freezing point of water is referenced as 0^oC. The boiling point of water is 100 ^oC.

Different thermometers have different capabilities in measuring temperatures both in terms of accuracy and range.

Now, am sure you have seen digital termometers. Digital thermometers do not use alcohol nor mercury, instead they use heat sensors that can detect the temperature based on the heat.

Conduction: Conduction occurs when thermal energy is transferred between two objects that are touching/are in contact. If you heat one side of a spoon on a flame, with time the entire spoon will become hot, even the parts that were not in contact with the hot water. Conduction occurs between the spoon and the flame. Because they are in contact, thermal energy is conducted from the flame to the spoon. This is followed by the conduction of thermal energy within the spoon, from the parts of the spoon that were hotter, to parts that were colder, until the whole spoon is more or less equally hot.

Convection: This is the transfer of thermal energy through a liquid or a gas. If you boil water in a pot, the water at the bottom of the pot get hot first/faster, then heat is transferred from the water in the bottom to the water at the top of the pot.

Radiation: Radiation is the transfer of energy through space. Without radiation, energy from the Sun would not reach Earth. Matter does not need to be present for radiation to occur.

Insulators and Conductors: Insulators are materials that do not transfer thermal energy well. As in, they prevent the transfer of thermal energy. One good use of insulators is in making handles for cooking pans/pots. Wood is a good example of an insulator. In humans and animals, fat acts as an insulator. Fat prevents the transfer of thermal energy, which is why bears gain fat just before winter so as to prepare them to concerve more thermal energy during winter.

Conductors (kinda as the name suggests) are materials that can effectively conduct heat, as in they are good at transferring thermal energy. Most metals are good conductors of heat, which is why cooking pots are made from metals. Clay is a poor conductor of heat, which means it takes longer to get hot but also takes longer to lose the heat (cool down), this property makes clay materials good for slow cooking.

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