Aim: Understand how scientists work and the importance of measurement. You will learn The method scientists use to investigate a problem. Learn how we observe things in the world and realise how our sense can give the wrong information sometimes. Be able to understand the different units of measurement. Learn how to measure length, the instruments used, and how to avoid errors. Learn how to measure time, mass and temperature and their units. Learn how to use common prefixes with regard to units of measure.

Keywords

Measurement and Units Scientific Method The scientific method is a way to ask and answer scientific questions by making observations and doing experiments. The steps of the scientific method are to:

Scientific Method Ask a Question Do Background Research Suggest a Hypothesis (explanation) Test Your Hypothesis by Doing an Exer ment Analyze Your Data and Draw a Conclusion Tell others your Results

Scientific Method It is important for your experiment to be a fair test. A "fair test" occurs when you change only one factor (variable) and keep all other conditions the same.

Scientific Method

Measuring Scientists do experiments and with measuring instruments can make accurate observations. We cannot always trust our senses, one the reasons why measuring is important.

Measurment Which line is the longest a or b? In fact they are both the same length.

Measurement Which man is the tallest? In fact they are all the same height So we must be careful of ours senses

Measuring Length Length is measured in units called metres (m). Where did metres come from? Show video clip on measurement. Common Units 1 m 100 cm 1m 1000 mm 1 km 1000 m

Measuring length

Measuring Length Metre stick (nearest mm) Measuring tape (nearest mm) Callipers (nearest mm)

Measuring Length Vernier Callipers (nearest 0.1 mm) measures small lengths and thicknesses.

Measuring Length Opisometer (nearest mm) measures length of curved lines

Measuring Length Trundle Wheel (nearest cm) measure longer lengths eg. Curved or straight lines on football pitches.

Measuring Mass Mass is the amount of matter or stuff in an object, measured using electronic balance in grams (g) or kilograms (kg) How can the mass of a liquid be measured?

Measuring Time Time is measured in seconds, minutes, hours, days and years. Measured using a stopwatch in the laboratory.

Measuring Temperature The temperature of an object is measure of how hot or cold an object is measured in degrees celcius (oC) Temperature of the body is 37 oC Pure water freezes at 0 oC and boils at 100 oC Temperatures below 0 oC have a minus value.

Measuring Temperature Four types of thermometer (a) mercury (b) alcohol (c) digital (d) clinical

Units and Prefixes Prefixc Symbol Unit multiplied by milli- m 1/1000 or 0.001 or 10-3 centi- c 1/100 or 0.01 or 10-2 deci- d 1/10 or 0.1 or 10-1 hecto- h 100 or 102 kilo- k 1000 or 103 mega- M 1000000 or 106

Area The area of a shape is the amount of surface enclosed by it. Area is measured in cm2 or m2 1m2 = 1m x 1m = 100cm x 100cm = 10,000 cm2 Area of a rectangle = length by width.

Area Area of a square = length by length

Area The area of a triangle = half the base x perpendicular height.

Area Area of circle = π x radius x radius (πr2)

Area EXAMPLE 1 Which of the following has the greatest area? (1) a rectangle of length 12.5 m and width 4. (2) a square of length 7 m (3) a triangle of base 13 m and height 8 m. Do the above problems in your copy book. (1) area of rectangle = length x width = 12.5 x 4 = 50 m2 (2) area of square = length x length = 7 x 7 = 49 m2

Area (3) Area of a triangle = ½base x perpendicular height. = 52 m2 EXAMPLE 2 How many times bigger is pizza A than pizza B if A has a radius of 20 cm and B a radius of 10 cm. Area of Pizza A radius 20 cm = πr2 = π 20 x 20 = 400π cm2 Area of Pizza B radius 10 cm = πr2 = π 10 x 10 = 100π cm2 SO PIZZA A IS FOUR TIMES THE AREA OF PIZZA B

Volume The volume of an object is the amount of space it takes up. Volume is measured in cubic metres (m3) or cubic centimetres (cm3) or litres = 1000 cm3 Volume in the laboratory is measured with measuring pipettes Burettes cylinders

Volume The volume of a regular object = length x width x height. EXAMPLE What is volume of a rectangular object length 10 m width 5 m and height 2 m Volume = length x width x height = 10 x 5 x 2 = 100 m3 How could you measure the volume of stone?

Volume Measuring the volume of an irregular object is got my displacement of a liquid (e.g. water) either by the rise in water level or displacement of water into a measuring cylinder.