Matter is anything that has mass, occupies volume and has properties that we can measure.

Transcription

1 1. Matter. Matter is anything that has mass, occupies volume and has properties that we can measure. All the objects around us occupy space, but this space is not always very clearly defined. For example, trees and stones have very clearly defined boundaries, but water and the ground do not. Matter forms all the bodies in the Universe Properties of matter The properties of matter are those qualities that describe and identify it. They can be: - General properties: These properties are common to all matter. For example mass, volume, weight and density. - Specific properties: These are the characteristics that differentiate one kind of matter from another. They can be used to describe and identify matter. They are colour, shape, size, texture, hardness, etc State which of the following concept are matter. Then explain why. Beauty Water Freedom Tree Paper Glass Sadness 1.2. Imagine that you pull the plunger of the syringe of the picture filling it with air. Then you cover the tip of the syringe with your finger and push the plunger down trying to expel the air. a. Could you do it? b. What does this experiment show?

2 2. Measurement. Measure is to compare something with an established model or pattern to know how many times the object contains it. Measurement is a method of determining it. We can classify the properties of matter in two groups: Quantitative properties of matter are those that we can count and measure, such as distance and time. They are called magnitudes (or quantities) Qualitative properties are those that we can't count or measure, such as smell, taste, lustre or smoothness Magnitudes and units A magnitude is a property of matter that can be measured, such as length, mass, time, temperature or force. To measure something, we need a standard, constant unit of measurement. This unit must also be easy to reproduce and to use. Magnitudes are represented by symbols, usually by a letter from the Greek or Latin alphabet. For example, mass is represented by the letter m and temperature by the letter T. Measurements are expressed by a number and the corresponding unit of the quantity that we are measuring: for example, Pepe is 1.67 m (metres) tall or The jug contains 2 L (litres) of water. To measure, we need an appropriate instrument too, such a ruler (length), a thermometer (temperature), a scale (mass), etc The international system of units A system of units is a scientific method of expressing the values of magnitudes using their corresponding units of measurement. The International System of Units (SI) establishes the magnitudes and their correspondent units of measurement. However, these unit are too big or too small, so multiples or fractions of them are used instead. For example a kilometre is equivalent to metres or a centimetre is equivalent to 0.01 metres. The units can be: - Base units. They are not derived from other magnitude. They are length, mass, time, temperature, force and electric charge. - Derived units. They are derived from one or more base units. They are surface area, volume, density, speed, etc.

3 2.1. Answer the questions about magnitudes and units of measurement: a. What is a magnitude? Put some examples. b. What characteristics have to have a unit of measurement? c. How are represented a magnitude? And a measurement? Put some example. d. What we need to measure a magnitude? Put some example. e. What is the difference between base units and derived units?

4 3. Length, surface area and volume Length Length is the distance between two points. It is used to express how long a body is. Length is a base unit. In the International System of Units, length is measured in metres (m) The instrument we used to measure length is the ruler or the tape measure Surface area Surface area is the extension occupied by a body in two dimensions (length and width). It is used to express how wide this body is. It is a derived unit from length. It is the result to multiply length by height of an object. In the International System of Units, surface is measured in square metres (m 2 ). To calculate the surface area of regular shaped bodies we use the mathematical equation corresponding to the shape. With irregular shaped bodies we divide the surface into regular ones, and calculate the surface of each one. Then, we add these areas together to calculate the total Volume Volume is the amount of space occupied by a body. It is used to express how large a body is. It is a derived unit from length too. It is the result to multiply length by height by width of an object. In the International System of Units, surface is measured in cubic metres (m 3 ).

5 In the case of regular geometric solids, we can use the corresponding mathematical formula. In the case of irregular-shaped solids, we must use a measuring cylinder. We submerge the body in water, and then we can measure the amount of displaced water. With liquids, we can directly use a measuring cylinder. And with gases, first we have to fill a measuring cylinder with water. Then, place it upside down in a dish of water and mark the water level in the cylinder: it is the initial volume. Next, blow air through a tube into the cylinder. The air displaces some water. We have to mark the new water level. It is the final volume. The difference between the two levels is the volume of gas. Related to the volume is the capacity of an object. Capacity is the maximum volume a container can contain. The litre is the unit of capacity we use most often. The relation between volume and capacity is: 1 dm 3 = 1 litre 3.1. Which multiples and submultiples of the metre would you use to calculate the following measurements? a. The distance between two towns. b. The diameter of the head of a nail. c. The length of your pen. d. The length of the classroom Your school wants to build a new sports field. Indicate how many square metres are needed for it, if it needs to include: - A football pitch measuring 100m x 100m. - A basketball court measuring 18m x 15 m. - A tennis court measuring m x 8.23 m A small carton has a capacity of 200 ml. What volume of juice can it contain? Express it in cm 3 and in m 3.

6 4. Mass. Mass is the amount of matter in a body. Mass is a base unit. The SI unit to measure mass is the kilogram (kg) The instrument used to measure mass is the scale. Mass is not the same than weight. Weight is the force with which the Earth attracts a body What is the difference between mass and weight? 4.2. A gold chain has weighted using a scale. We have needed 4 weights to do it: one 100g weight, two 1 g weight and one 500 mg weigth. Can you calculate the mass of the chain in grams and milligrams?

7 5. Density. Density is the relationship between the mass and the volume of a body. Density = Mass Volume In other words, density represent how concentrated the mass is in a specific volume. Density is measured in kg/m 3 (International System of Units) or g/cm 3. For example, iron has a higher density than wood. Imagine two blocks, one of iron, and one of wood, have the same volume. The block of iron has more mass, or amount of matter, so it is harder to move. Other example is represented in the pictures below: The same volume of different substances has different masses. So the density of these substances is different too. Density is a specific property of matter. It helps differentiate one substance from another. Generally speaking, solids have a higher density than liquids, and liquids have a higher density than gases cm 3 of water are poured in a container of 200 cm 3. Then a stone of 100 g is introduced onto it. As a result, the water level increases until 225 cm 3. a. What is the volume of the stone? b. What is its density? 5.2. Why does not the iron float on water, but mercury does?

8 6. Temperature and time Temperature Temperature is used to measure the thermal state of a body. This measurement is related to the body's internal state. Temperature represents the amount of heat a body gives off or absorbs. A hot body will heat a cold one until they are both the same temperature. The instrument used to measure the temperature of bodies is the thermometer. In the International System of Units, the kelvin (K) is the unit for temperature. Another unit, degrees Celsius ( C) is used more frequently. Some countries, (especially the United States of America) use another measurement, Fahrenheit ( F). Here are some equivalents: Temperature does not depend on the amount of matter. For example, imagine that the temperature of the water in a glass is 60 C. If you pour half of the water into one glass and half in another, the temperature in each one will still be 60 C Time Time is used to measure the passing of events. In the International System of Units, time is measured in seconds (s) and the instrument used to measure it is the chronometer What we use these instruments for? a. Thermometer b. Chronometer